Initial import

1 files changed, 2408 insertions, 0 deletions

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
new file mode 100644
index 000000000..d35c1a132
--- /dev/null
+++ b/drivers/spi/spi.c
@@ -0,0 +1,2408 @@
+/*
+ * SPI init/core code
+ *
+ * Copyright (C) 2005 David Brownell
+ * Copyright (C) 2008 Secret Lab Technologies Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/cache.h>
+#include <linux/dma-mapping.h>
+#include <linux/dmaengine.h>
+#include <linux/mutex.h>
+#include <linux/of_device.h>
+#include <linux/of_irq.h>
+#include <linux/clk/clk-conf.h>
+#include <linux/slab.h>
+#include <linux/mod_devicetable.h>
+#include <linux/spi/spi.h>
+#include <linux/of_gpio.h>
+#include <linux/pm_runtime.h>
+#include <linux/pm_domain.h>
+#include <linux/export.h>
+#include <linux/sched/rt.h>
+#include <linux/delay.h>
+#include <linux/kthread.h>
+#include <linux/ioport.h>
+#include <linux/acpi.h>
+
+#define CREATE_TRACE_POINTS
+#include <trace/events/spi.h>
+
+static void spidev_release(struct device *dev)
+{
+	struct spi_device	*spi = to_spi_device(dev);
+
+	/* spi masters may cleanup for released devices */
+	if (spi->master->cleanup)
+		spi->master->cleanup(spi);
+
+	spi_master_put(spi->master);
+	kfree(spi);
+}
+
+static ssize_t
+modalias_show(struct device *dev, struct device_attribute *a, char *buf)
+{
+	const struct spi_device	*spi = to_spi_device(dev);
+	int len;
+
+	len = acpi_device_modalias(dev, buf, PAGE_SIZE - 1);
+	if (len != -ENODEV)
+		return len;
+
+	return sprintf(buf, "%s%s\n", SPI_MODULE_PREFIX, spi->modalias);
+}
+static DEVICE_ATTR_RO(modalias);
+
+static struct attribute *spi_dev_attrs[] = {
+	&dev_attr_modalias.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(spi_dev);
+
+/* modalias support makes "modprobe $MODALIAS" new-style hotplug work,
+ * and the sysfs version makes coldplug work too.
+ */
+
+static const struct spi_device_id *spi_match_id(const struct spi_device_id *id,
+						const struct spi_device *sdev)
+{
+	while (id->name[0]) {
+		if (!strcmp(sdev->modalias, id->name))
+			return id;
+		id++;
+	}
+	return NULL;
+}
+
+const struct spi_device_id *spi_get_device_id(const struct spi_device *sdev)
+{
+	const struct spi_driver *sdrv = to_spi_driver(sdev->dev.driver);
+
+	return spi_match_id(sdrv->id_table, sdev);
+}
+EXPORT_SYMBOL_GPL(spi_get_device_id);
+
+static int spi_match_device(struct device *dev, struct device_driver *drv)
+{
+	const struct spi_device	*spi = to_spi_device(dev);
+	const struct spi_driver	*sdrv = to_spi_driver(drv);
+
+	/* Attempt an OF style match */
+	if (of_driver_match_device(dev, drv))
+		return 1;
+
+	/* Then try ACPI */
+	if (acpi_driver_match_device(dev, drv))
+		return 1;
+
+	if (sdrv->id_table)
+		return !!spi_match_id(sdrv->id_table, spi);
+
+	return strcmp(spi->modalias, drv->name) == 0;
+}
+
+static int spi_uevent(struct device *dev, struct kobj_uevent_env *env)
+{
+	const struct spi_device		*spi = to_spi_device(dev);
+	int rc;
+
+	rc = acpi_device_uevent_modalias(dev, env);
+	if (rc != -ENODEV)
+		return rc;
+
+	add_uevent_var(env, "MODALIAS=%s%s", SPI_MODULE_PREFIX, spi->modalias);
+	return 0;
+}
+
+struct bus_type spi_bus_type = {
+	.name		= "spi",
+	.dev_groups	= spi_dev_groups,
+	.match		= spi_match_device,
+	.uevent		= spi_uevent,
+};
+EXPORT_SYMBOL_GPL(spi_bus_type);
+
+
+static int spi_drv_probe(struct device *dev)
+{
+	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);
+	int ret;
+
+	ret = of_clk_set_defaults(dev->of_node, false);
+	if (ret)
+		return ret;
+
+	ret = dev_pm_domain_attach(dev, true);
+	if (ret != -EPROBE_DEFER) {
+		ret = sdrv->probe(to_spi_device(dev));
+		if (ret)
+			dev_pm_domain_detach(dev, true);
+	}
+
+	return ret;
+}
+
+static int spi_drv_remove(struct device *dev)
+{
+	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);
+	int ret;
+
+	ret = sdrv->remove(to_spi_device(dev));
+	dev_pm_domain_detach(dev, true);
+
+	return ret;
+}
+
+static void spi_drv_shutdown(struct device *dev)
+{
+	const struct spi_driver		*sdrv = to_spi_driver(dev->driver);
+
+	sdrv->shutdown(to_spi_device(dev));
+}
+
+/**
+ * spi_register_driver - register a SPI driver
+ * @sdrv: the driver to register
+ * Context: can sleep
+ */
+int spi_register_driver(struct spi_driver *sdrv)
+{
+	sdrv->driver.bus = &spi_bus_type;
+	if (sdrv->probe)
+		sdrv->driver.probe = spi_drv_probe;
+	if (sdrv->remove)
+		sdrv->driver.remove = spi_drv_remove;
+	if (sdrv->shutdown)
+		sdrv->driver.shutdown = spi_drv_shutdown;
+	return driver_register(&sdrv->driver);
+}
+EXPORT_SYMBOL_GPL(spi_register_driver);
+
+/*-------------------------------------------------------------------------*/
+
+/* SPI devices should normally not be created by SPI device drivers; that
+ * would make them board-specific.  Similarly with SPI master drivers.
+ * Device registration normally goes into like arch/.../mach.../board-YYY.c
+ * with other readonly (flashable) information about mainboard devices.
+ */
+
+struct boardinfo {
+	struct list_head	list;
+	struct spi_board_info	board_info;
+};
+
+static LIST_HEAD(board_list);
+static LIST_HEAD(spi_master_list);
+
+/*
+ * Used to protect add/del opertion for board_info list and
+ * spi_master list, and their matching process
+ */
+static DEFINE_MUTEX(board_lock);
+
+/**
+ * spi_alloc_device - Allocate a new SPI device
+ * @master: Controller to which device is connected
+ * Context: can sleep
+ *
+ * Allows a driver to allocate and initialize a spi_device without
+ * registering it immediately.  This allows a driver to directly
+ * fill the spi_device with device parameters before calling
+ * spi_add_device() on it.
+ *
+ * Caller is responsible to call spi_add_device() on the returned
+ * spi_device structure to add it to the SPI master.  If the caller
+ * needs to discard the spi_device without adding it, then it should
+ * call spi_dev_put() on it.
+ *
+ * Returns a pointer to the new device, or NULL.
+ */
+struct spi_device *spi_alloc_device(struct spi_master *master)
+{
+	struct spi_device	*spi;
+
+	if (!spi_master_get(master))
+		return NULL;
+
+	spi = kzalloc(sizeof(*spi), GFP_KERNEL);
+	if (!spi) {
+		spi_master_put(master);
+		return NULL;
+	}
+
+	spi->master = master;
+	spi->dev.parent = &master->dev;
+	spi->dev.bus = &spi_bus_type;
+	spi->dev.release = spidev_release;
+	spi->cs_gpio = -ENOENT;
+	device_initialize(&spi->dev);
+	return spi;
+}
+EXPORT_SYMBOL_GPL(spi_alloc_device);
+
+static void spi_dev_set_name(struct spi_device *spi)
+{
+	struct acpi_device *adev = ACPI_COMPANION(&spi->dev);
+
+	if (adev) {
+		dev_set_name(&spi->dev, "spi-%s", acpi_dev_name(adev));
+		return;
+	}
+
+	dev_set_name(&spi->dev, "%s.%u", dev_name(&spi->master->dev),
+		     spi->chip_select);
+}
+
+static int spi_dev_check(struct device *dev, void *data)
+{
+	struct spi_device *spi = to_spi_device(dev);
+	struct spi_device *new_spi = data;
+
+	if (spi->master == new_spi->master &&
+	    spi->chip_select == new_spi->chip_select)
+		return -EBUSY;
+	return 0;
+}
+
+/**
+ * spi_add_device - Add spi_device allocated with spi_alloc_device
+ * @spi: spi_device to register
+ *
+ * Companion function to spi_alloc_device.  Devices allocated with
+ * spi_alloc_device can be added onto the spi bus with this function.
+ *
+ * Returns 0 on success; negative errno on failure
+ */
+int spi_add_device(struct spi_device *spi)
+{
+	static DEFINE_MUTEX(spi_add_lock);
+	struct spi_master *master = spi->master;
+	struct device *dev = master->dev.parent;
+	int status;
+
+	/* Chipselects are numbered 0..max; validate. */
+	if (spi->chip_select >= master->num_chipselect) {
+		dev_err(dev, "cs%d >= max %d\n",
+			spi->chip_select,
+			master->num_chipselect);
+		return -EINVAL;
+	}
+
+	/* Set the bus ID string */
+	spi_dev_set_name(spi);
+
+	/* We need to make sure there's no other device with this
+	 * chipselect **BEFORE** we call setup(), else we'll trash
+	 * its configuration.  Lock against concurrent add() calls.
+	 */
+	mutex_lock(&spi_add_lock);
+
+	status = bus_for_each_dev(&spi_bus_type, NULL, spi, spi_dev_check);
+	if (status) {
+		dev_err(dev, "chipselect %d already in use\n",
+				spi->chip_select);
+		goto done;
+	}
+
+	if (master->cs_gpios)
+		spi->cs_gpio = master->cs_gpios[spi->chip_select];
+
+	/* Drivers may modify this initial i/o setup, but will
+	 * normally rely on the device being setup.  Devices
+	 * using SPI_CS_HIGH can't coexist well otherwise...
+	 */
+	status = spi_setup(spi);
+	if (status < 0) {
+		dev_err(dev, "can't setup %s, status %d\n",
+				dev_name(&spi->dev), status);
+		goto done;
+	}
+
+	/* Device may be bound to an active driver when this returns */
+	status = device_add(&spi->dev);
+	if (status < 0)
+		dev_err(dev, "can't add %s, status %d\n",
+				dev_name(&spi->dev), status);
+	else
+		dev_dbg(dev, "registered child %s\n", dev_name(&spi->dev));
+
+done:
+	mutex_unlock(&spi_add_lock);
+	return status;
+}
+EXPORT_SYMBOL_GPL(spi_add_device);
+
+/**
+ * spi_new_device - instantiate one new SPI device
+ * @master: Controller to which device is connected
+ * @chip: Describes the SPI device
+ * Context: can sleep
+ *
+ * On typical mainboards, this is purely internal; and it's not needed
+ * after board init creates the hard-wired devices.  Some development
+ * platforms may not be able to use spi_register_board_info though, and
+ * this is exported so that for example a USB or parport based adapter
+ * driver could add devices (which it would learn about out-of-band).
+ *
+ * Returns the new device, or NULL.
+ */
+struct spi_device *spi_new_device(struct spi_master *master,
+				  struct spi_board_info *chip)
+{
+	struct spi_device	*proxy;
+	int			status;
+
+	/* NOTE:  caller did any chip->bus_num checks necessary.
+	 *
+	 * Also, unless we change the return value convention to use
+	 * error-or-pointer (not NULL-or-pointer), troubleshootability
+	 * suggests syslogged diagnostics are best here (ugh).
+	 */
+
+	proxy = spi_alloc_device(master);
+	if (!proxy)
+		return NULL;
+
+	WARN_ON(strlen(chip->modalias) >= sizeof(proxy->modalias));
+
+	proxy->chip_select = chip->chip_select;
+	proxy->max_speed_hz = chip->max_speed_hz;
+	proxy->mode = chip->mode;
+	proxy->irq = chip->irq;
+	strlcpy(proxy->modalias, chip->modalias, sizeof(proxy->modalias));
+	proxy->dev.platform_data = (void *) chip->platform_data;
+	proxy->controller_data = chip->controller_data;
+	proxy->controller_state = NULL;
+
+	status = spi_add_device(proxy);
+	if (status < 0) {
+		spi_dev_put(proxy);
+		return NULL;
+	}
+
+	return proxy;
+}
+EXPORT_SYMBOL_GPL(spi_new_device);
+
+static void spi_match_master_to_boardinfo(struct spi_master *master,
+				struct spi_board_info *bi)
+{
+	struct spi_device *dev;
+
+	if (master->bus_num != bi->bus_num)
+		return;
+
+	dev = spi_new_device(master, bi);
+	if (!dev)
+		dev_err(master->dev.parent, "can't create new device for %s\n",
+			bi->modalias);
+}
+
+/**
+ * spi_register_board_info - register SPI devices for a given board
+ * @info: array of chip descriptors
+ * @n: how many descriptors are provided
+ * Context: can sleep
+ *
+ * Board-specific early init code calls this (probably during arch_initcall)
+ * with segments of the SPI device table.  Any device nodes are created later,
+ * after the relevant parent SPI controller (bus_num) is defined.  We keep
+ * this table of devices forever, so that reloading a controller driver will
+ * not make Linux forget about these hard-wired devices.
+ *
+ * Other code can also call this, e.g. a particular add-on board might provide
+ * SPI devices through its expansion connector, so code initializing that board
+ * would naturally declare its SPI devices.
+ *
+ * The board info passed can safely be __initdata ... but be careful of
+ * any embedded pointers (platform_data, etc), they're copied as-is.
+ */
+int spi_register_board_info(struct spi_board_info const *info, unsigned n)
+{
+	struct boardinfo *bi;
+	int i;
+
+	if (!n)
+		return -EINVAL;
+
+	bi = kzalloc(n * sizeof(*bi), GFP_KERNEL);
+	if (!bi)
+		return -ENOMEM;
+
+	for (i = 0; i < n; i++, bi++, info++) {
+		struct spi_master *master;
+
+		memcpy(&bi->board_info, info, sizeof(*info));
+		mutex_lock(&board_lock);
+		list_add_tail(&bi->list, &board_list);
+		list_for_each_entry(master, &spi_master_list, list)
+			spi_match_master_to_boardinfo(master, &bi->board_info);
+		mutex_unlock(&board_lock);
+	}
+
+	return 0;
+}
+
+/*-------------------------------------------------------------------------*/
+
+static void spi_set_cs(struct spi_device *spi, bool enable)
+{
+	if (spi->mode & SPI_CS_HIGH)
+		enable = !enable;
+
+	if (spi->cs_gpio >= 0)
+		gpio_set_value(spi->cs_gpio, !enable);
+	else if (spi->master->set_cs)
+		spi->master->set_cs(spi, !enable);
+}
+
+#ifdef CONFIG_HAS_DMA
+static int spi_map_buf(struct spi_master *master, struct device *dev,
+		       struct sg_table *sgt, void *buf, size_t len,
+		       enum dma_data_direction dir)
+{
+	const bool vmalloced_buf = is_vmalloc_addr(buf);
+	const int desc_len = vmalloced_buf ? PAGE_SIZE : master->max_dma_len;
+	const int sgs = DIV_ROUND_UP(len, desc_len);
+	struct page *vm_page;
+	void *sg_buf;
+	size_t min;
+	int i, ret;
+
+	ret = sg_alloc_table(sgt, sgs, GFP_KERNEL);
+	if (ret != 0)
+		return ret;
+
+	for (i = 0; i < sgs; i++) {
+		min = min_t(size_t, len, desc_len);
+
+		if (vmalloced_buf) {
+			vm_page = vmalloc_to_page(buf);
+			if (!vm_page) {
+				sg_free_table(sgt);
+				return -ENOMEM;
+			}
+			sg_set_page(&sgt->sgl[i], vm_page,
+				    min, offset_in_page(buf));
+		} else {
+			sg_buf = buf;
+			sg_set_buf(&sgt->sgl[i], sg_buf, min);
+		}
+
+
+		buf += min;
+		len -= min;
+	}
+
+	ret = dma_map_sg(dev, sgt->sgl, sgt->nents, dir);
+	if (!ret)
+		ret = -ENOMEM;
+	if (ret < 0) {
+		sg_free_table(sgt);
+		return ret;
+	}
+
+	sgt->nents = ret;
+
+	return 0;
+}
+
+static void spi_unmap_buf(struct spi_master *master, struct device *dev,
+			  struct sg_table *sgt, enum dma_data_direction dir)
+{
+	if (sgt->orig_nents) {
+		dma_unmap_sg(dev, sgt->sgl, sgt->orig_nents, dir);
+		sg_free_table(sgt);
+	}
+}
+
+static int __spi_map_msg(struct spi_master *master, struct spi_message *msg)
+{
+	struct device *tx_dev, *rx_dev;
+	struct spi_transfer *xfer;
+	int ret;
+
+	if (!master->can_dma)
+		return 0;
+
+	tx_dev = master->dma_tx->device->dev;
+	rx_dev = master->dma_rx->device->dev;
+
+	list_for_each_entry(xfer, &msg->transfers, transfer_list) {
+		if (!master->can_dma(master, msg->spi, xfer))
+			continue;
+
+		if (xfer->tx_buf != NULL) {
+			ret = spi_map_buf(master, tx_dev, &xfer->tx_sg,
+					  (void *)xfer->tx_buf, xfer->len,
+					  DMA_TO_DEVICE);
+			if (ret != 0)
+				return ret;
+		}
+
+		if (xfer->rx_buf != NULL) {
+			ret = spi_map_buf(master, rx_dev, &xfer->rx_sg,
+					  xfer->rx_buf, xfer->len,
+					  DMA_FROM_DEVICE);
+			if (ret != 0) {
+				spi_unmap_buf(master, tx_dev, &xfer->tx_sg,
+					      DMA_TO_DEVICE);
+				return ret;
+			}
+		}
+	}
+
+	master->cur_msg_mapped = true;
+
+	return 0;
+}
+
+static int spi_unmap_msg(struct spi_master *master, struct spi_message *msg)
+{
+	struct spi_transfer *xfer;
+	struct device *tx_dev, *rx_dev;
+
+	if (!master->cur_msg_mapped || !master->can_dma)
+		return 0;
+
+	tx_dev = master->dma_tx->device->dev;
+	rx_dev = master->dma_rx->device->dev;
+
+	list_for_each_entry(xfer, &msg->transfers, transfer_list) {
+		/*
+		 * Restore the original value of tx_buf or rx_buf if they are
+		 * NULL.
+		 */
+		if (xfer->tx_buf == master->dummy_tx)
+			xfer->tx_buf = NULL;
+		if (xfer->rx_buf == master->dummy_rx)
+			xfer->rx_buf = NULL;
+
+		if (!master->can_dma(master, msg->spi, xfer))
+			continue;
+
+		spi_unmap_buf(master, rx_dev, &xfer->rx_sg, DMA_FROM_DEVICE);
+		spi_unmap_buf(master, tx_dev, &xfer->tx_sg, DMA_TO_DEVICE);
+	}
+
+	return 0;
+}
+#else /* !CONFIG_HAS_DMA */
+static inline int __spi_map_msg(struct spi_master *master,
+				struct spi_message *msg)
+{
+	return 0;
+}
+
+static inline int spi_unmap_msg(struct spi_master *master,
+				struct spi_message *msg)
+{
+	return 0;
+}
+#endif /* !CONFIG_HAS_DMA */
+
+static int spi_map_msg(struct spi_master *master, struct spi_message *msg)
+{
+	struct spi_transfer *xfer;
+	void *tmp;
+	unsigned int max_tx, max_rx;
+
+	if (master->flags & (SPI_MASTER_MUST_RX | SPI_MASTER_MUST_TX)) {
+		max_tx = 0;
+		max_rx = 0;
+
+		list_for_each_entry(xfer, &msg->transfers, transfer_list) {
+			if ((master->flags & SPI_MASTER_MUST_TX) &&
+			    !xfer->tx_buf)
+				max_tx = max(xfer->len, max_tx);
+			if ((master->flags & SPI_MASTER_MUST_RX) &&
+			    !xfer->rx_buf)
+				max_rx = max(xfer->len, max_rx);
+		}
+
+		if (max_tx) {
+			tmp = krealloc(master->dummy_tx, max_tx,
+				       GFP_KERNEL | GFP_DMA);
+			if (!tmp)
+				return -ENOMEM;
+			master->dummy_tx = tmp;
+			memset(tmp, 0, max_tx);
+		}
+
+		if (max_rx) {
+			tmp = krealloc(master->dummy_rx, max_rx,
+				       GFP_KERNEL | GFP_DMA);
+			if (!tmp)
+				return -ENOMEM;
+			master->dummy_rx = tmp;
+		}
+
+		if (max_tx || max_rx) {
+			list_for_each_entry(xfer, &msg->transfers,
+					    transfer_list) {
+				if (!xfer->tx_buf)
+					xfer->tx_buf = master->dummy_tx;
+				if (!xfer->rx_buf)
+					xfer->rx_buf = master->dummy_rx;
+			}
+		}
+	}
+
+	return __spi_map_msg(master, msg);
+}
+
+/*
+ * spi_transfer_one_message - Default implementation of transfer_one_message()
+ *
+ * This is a standard implementation of transfer_one_message() for
+ * drivers which impelment a transfer_one() operation.  It provides
+ * standard handling of delays and chip select management.
+ */
+static int spi_transfer_one_message(struct spi_master *master,
+				    struct spi_message *msg)
+{
+	struct spi_transfer *xfer;
+	bool keep_cs = false;
+	int ret = 0;
+	unsigned long ms = 1;
+
+	spi_set_cs(msg->spi, true);
+
+	list_for_each_entry(xfer, &msg->transfers, transfer_list) {
+		trace_spi_transfer_start(msg, xfer);
+
+		if (xfer->tx_buf || xfer->rx_buf) {
+			reinit_completion(&master->xfer_completion);
+
+			ret = master->transfer_one(master, msg->spi, xfer);
+			if (ret < 0) {
+				dev_err(&msg->spi->dev,
+					"SPI transfer failed: %d\n", ret);
+				goto out;
+			}
+
+			if (ret > 0) {
+				ret = 0;
+				ms = xfer->len * 8 * 1000 / xfer->speed_hz;
+				ms += ms + 100; /* some tolerance */
+
+				ms = wait_for_completion_timeout(&master->xfer_completion,
+								 msecs_to_jiffies(ms));
+			}
+
+			if (ms == 0) {
+				dev_err(&msg->spi->dev,
+					"SPI transfer timed out\n");
+				msg->status = -ETIMEDOUT;
+			}
+		} else {
+			if (xfer->len)
+				dev_err(&msg->spi->dev,
+					"Bufferless transfer has length %u\n",
+					xfer->len);
+		}
+
+		trace_spi_transfer_stop(msg, xfer);
+
+		if (msg->status != -EINPROGRESS)
+			goto out;
+
+		if (xfer->delay_usecs)
+			udelay(xfer->delay_usecs);
+
+		if (xfer->cs_change) {
+			if (list_is_last(&xfer->transfer_list,
+					 &msg->transfers)) {
+				keep_cs = true;
+			} else {
+				spi_set_cs(msg->spi, false);
+				udelay(10);
+				spi_set_cs(msg->spi, true);
+			}
+		}
+
+		msg->actual_length += xfer->len;
+	}
+
+out:
+	if (ret != 0 || !keep_cs)
+		spi_set_cs(msg->spi, false);
+
+	if (msg->status == -EINPROGRESS)
+		msg->status = ret;
+
+	if (msg->status && master->handle_err)
+		master->handle_err(master, msg);
+
+	spi_finalize_current_message(master);
+
+	return ret;
+}
+
+/**
+ * spi_finalize_current_transfer - report completion of a transfer
+ * @master: the master reporting completion
+ *
+ * Called by SPI drivers using the core transfer_one_message()
+ * implementation to notify it that the current interrupt driven
+ * transfer has finished and the next one may be scheduled.
+ */
+void spi_finalize_current_transfer(struct spi_master *master)
+{
+	complete(&master->xfer_completion);
+}
+EXPORT_SYMBOL_GPL(spi_finalize_current_transfer);
+
+/**
+ * __spi_pump_messages - function which processes spi message queue
+ * @master: master to process queue for
+ * @in_kthread: true if we are in the context of the message pump thread
+ *
+ * This function checks if there is any spi message in the queue that
+ * needs processing and if so call out to the driver to initialize hardware
+ * and transfer each message.
+ *
+ * Note that it is called both from the kthread itself and also from
+ * inside spi_sync(); the queue extraction handling at the top of the
+ * function should deal with this safely.
+ */
+static void __spi_pump_messages(struct spi_master *master, bool in_kthread)
+{
+	unsigned long flags;
+	bool was_busy = false;
+	int ret;
+
+	/* Lock queue */
+	spin_lock_irqsave(&master->queue_lock, flags);
+
+	/* Make sure we are not already running a message */
+	if (master->cur_msg) {
+		spin_unlock_irqrestore(&master->queue_lock, flags);
+		return;
+	}
+
+	/* If another context is idling the device then defer */
+	if (master->idling) {
+		queue_kthread_work(&master->kworker, &master->pump_messages);
+		spin_unlock_irqrestore(&master->queue_lock, flags);
+		return;
+	}
+
+	/* Check if the queue is idle */
+	if (list_empty(&master->queue) || !master->running) {
+		if (!master->busy) {
+			spin_unlock_irqrestore(&master->queue_lock, flags);
+			return;
+		}
+
+		/* Only do teardown in the thread */
+		if (!in_kthread) {
+			queue_kthread_work(&master->kworker,
+					   &master->pump_messages);
+			spin_unlock_irqrestore(&master->queue_lock, flags);
+			return;
+		}
+
+		master->busy = false;
+		master->idling = true;
+		spin_unlock_irqrestore(&master->queue_lock, flags);
+
+		kfree(master->dummy_rx);
+		master->dummy_rx = NULL;
+		kfree(master->dummy_tx);
+		master->dummy_tx = NULL;
+		if (master->unprepare_transfer_hardware &&
+		    master->unprepare_transfer_hardware(master))
+			dev_err(&master->dev,
+				"failed to unprepare transfer hardware\n");
+		if (master->auto_runtime_pm) {
+			pm_runtime_mark_last_busy(master->dev.parent);
+			pm_runtime_put_autosuspend(master->dev.parent);
+		}
+		trace_spi_master_idle(master);
+
+		spin_lock_irqsave(&master->queue_lock, flags);
+		master->idling = false;
+		spin_unlock_irqrestore(&master->queue_lock, flags);
+		return;
+	}
+
+	/* Extract head of queue */
+	master->cur_msg =
+		list_first_entry(&master->queue, struct spi_message, queue);
+
+	list_del_init(&master->cur_msg->queue);
+	if (master->busy)
+		was_busy = true;
+	else
+		master->busy = true;
+	spin_unlock_irqrestore(&master->queue_lock, flags);
+
+	if (!was_busy && master->auto_runtime_pm) {
+		ret = pm_runtime_get_sync(master->dev.parent);
+		if (ret < 0) {
+			dev_err(&master->dev, "Failed to power device: %d\n",
+				ret);
+			return;
+		}
+	}
+
+	if (!was_busy)
+		trace_spi_master_busy(master);
+
+	if (!was_busy && master->prepare_transfer_hardware) {
+		ret = master->prepare_transfer_hardware(master);
+		if (ret) {
+			dev_err(&master->dev,
+				"failed to prepare transfer hardware\n");
+
+			if (master->auto_runtime_pm)
+				pm_runtime_put(master->dev.parent);
+			return;
+		}
+	}
+
+	trace_spi_message_start(master->cur_msg);
+
+	if (master->prepare_message) {
+		ret = master->prepare_message(master, master->cur_msg);
+		if (ret) {
+			dev_err(&master->dev,
+				"failed to prepare message: %d\n", ret);
+			master->cur_msg->status = ret;
+			spi_finalize_current_message(master);
+			return;
+		}
+		master->cur_msg_prepared = true;
+	}
+
+	ret = spi_map_msg(master, master->cur_msg);
+	if (ret) {
+		master->cur_msg->status = ret;
+		spi_finalize_current_message(master);
+		return;
+	}
+
+	ret = master->transfer_one_message(master, master->cur_msg);
+	if (ret) {
+		dev_err(&master->dev,
+			"failed to transfer one message from queue\n");
+		return;
+	}
+}
+
+/**
+ * spi_pump_messages - kthread work function which processes spi message queue
+ * @work: pointer to kthread work struct contained in the master struct
+ */
+static void spi_pump_messages(struct kthread_work *work)
+{
+	struct spi_master *master =
+		container_of(work, struct spi_master, pump_messages);
+
+	__spi_pump_messages(master, true);
+}
+
+static int spi_init_queue(struct spi_master *master)
+{
+	struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 };
+
+	master->running = false;
+	master->busy = false;
+
+	init_kthread_worker(&master->kworker);
+	master->kworker_task = kthread_run(kthread_worker_fn,
+					   &master->kworker, "%s",
+					   dev_name(&master->dev));
+	if (IS_ERR(master->kworker_task)) {
+		dev_err(&master->dev, "failed to create message pump task\n");
+		return PTR_ERR(master->kworker_task);
+	}
+	init_kthread_work(&master->pump_messages, spi_pump_messages);
+
+	/*
+	 * Master config will indicate if this controller should run the
+	 * message pump with high (realtime) priority to reduce the transfer
+	 * latency on the bus by minimising the delay between a transfer
+	 * request and the scheduling of the message pump thread. Without this
+	 * setting the message pump thread will remain at default priority.
+	 */
+	if (master->rt) {
+		dev_info(&master->dev,
+			"will run message pump with realtime priority\n");
+		sched_setscheduler(master->kworker_task, SCHED_FIFO, &param);
+	}
+
+	return 0;
+}
+
+/**
+ * spi_get_next_queued_message() - called by driver to check for queued
+ * messages
+ * @master: the master to check for queued messages
+ *
+ * If there are more messages in the queue, the next message is returned from
+ * this call.
+ */
+struct spi_message *spi_get_next_queued_message(struct spi_master *master)
+{
+	struct spi_message *next;
+	unsigned long flags;
+
+	/* get a pointer to the next message, if any */
+	spin_lock_irqsave(&master->queue_lock, flags);
+	next = list_first_entry_or_null(&master->queue, struct spi_message,
+					queue);
+	spin_unlock_irqrestore(&master->queue_lock, flags);
+
+	return next;
+}
+EXPORT_SYMBOL_GPL(spi_get_next_queued_message);
+
+/**
+ * spi_finalize_current_message() - the current message is complete
+ * @master: the master to return the message to
+ *
+ * Called by the driver to notify the core that the message in the front of the
+ * queue is complete and can be removed from the queue.
+ */
+void spi_finalize_current_message(struct spi_master *master)
+{
+	struct spi_message *mesg;
+	unsigned long flags;
+	int ret;
+
+	spin_lock_irqsave(&master->queue_lock, flags);
+	mesg = master->cur_msg;
+	spin_unlock_irqrestore(&master->queue_lock, flags);
+
+	spi_unmap_msg(master, mesg);
+
+	if (master->cur_msg_prepared && master->unprepare_message) {
+		ret = master->unprepare_message(master, mesg);
+		if (ret) {
+			dev_err(&master->dev,
+				"failed to unprepare message: %d\n", ret);
+		}
+	}
+
+	spin_lock_irqsave(&master->queue_lock, flags);
+	master->cur_msg = NULL;
+	master->cur_msg_prepared = false;
+	queue_kthread_work(&master->kworker, &master->pump_messages);
+	spin_unlock_irqrestore(&master->queue_lock, flags);
+
+	trace_spi_message_done(mesg);
+
+	mesg->state = NULL;
+	if (mesg->complete)
+		mesg->complete(mesg->context);
+}
+EXPORT_SYMBOL_GPL(spi_finalize_current_message);
+
+static int spi_start_queue(struct spi_master *master)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&master->queue_lock, flags);
+
+	if (master->running || master->busy) {
+		spin_unlock_irqrestore(&master->queue_lock, flags);
+		return -EBUSY;
+	}
+
+	master->running = true;
+	master->cur_msg = NULL;
+	spin_unlock_irqrestore(&master->queue_lock, flags);
+
+	queue_kthread_work(&master->kworker, &master->pump_messages);
+
+	return 0;
+}
+
+static int spi_stop_queue(struct spi_master *master)
+{
+	unsigned long flags;
+	unsigned limit = 500;
+	int ret = 0;
+
+	spin_lock_irqsave(&master->queue_lock, flags);
+
+	/*
+	 * This is a bit lame, but is optimized for the common execution path.
+	 * A wait_queue on the master->busy could be used, but then the common
+	 * execution path (pump_messages) would be required to call wake_up or
+	 * friends on every SPI message. Do this instead.
+	 */
+	while ((!list_empty(&master->queue) || master->busy) && limit--) {
+		spin_unlock_irqrestore(&master->queue_lock, flags);
+		usleep_range(10000, 11000);
+		spin_lock_irqsave(&master->queue_lock, flags);
+	}
+
+	if (!list_empty(&master->queue) || master->busy)
+		ret = -EBUSY;
+	else
+		master->running = false;
+
+	spin_unlock_irqrestore(&master->queue_lock, flags);
+
+	if (ret) {
+		dev_warn(&master->dev,
+			 "could not stop message queue\n");
+		return ret;
+	}
+	return ret;
+}
+
+static int spi_destroy_queue(struct spi_master *master)
+{
+	int ret;
+
+	ret = spi_stop_queue(master);
+
+	/*
+	 * flush_kthread_worker will block until all work is done.
+	 * If the reason that stop_queue timed out is that the work will never
+	 * finish, then it does no good to call flush/stop thread, so
+	 * return anyway.
+	 */
+	if (ret) {
+		dev_err(&master->dev, "problem destroying queue\n");
+		return ret;
+	}
+
+	flush_kthread_worker(&master->kworker);
+	kthread_stop(master->kworker_task);
+
+	return 0;
+}
+
+static int __spi_queued_transfer(struct spi_device *spi,
+				 struct spi_message *msg,
+				 bool need_pump)
+{
+	struct spi_master *master = spi->master;
+	unsigned long flags;
+
+	spin_lock_irqsave(&master->queue_lock, flags);
+
+	if (!master->running) {
+		spin_unlock_irqrestore(&master->queue_lock, flags);
+		return -ESHUTDOWN;
+	}
+	msg->actual_length = 0;
+	msg->status = -EINPROGRESS;
+
+	list_add_tail(&msg->queue, &master->queue);
+	if (!master->busy && need_pump)
+		queue_kthread_work(&master->kworker, &master->pump_messages);
+
+	spin_unlock_irqrestore(&master->queue_lock, flags);
+	return 0;
+}
+
+/**
+ * spi_queued_transfer - transfer function for queued transfers
+ * @spi: spi device which is requesting transfer
+ * @msg: spi message which is to handled is queued to driver queue
+ */
+static int spi_queued_transfer(struct spi_device *spi, struct spi_message *msg)
+{
+	return __spi_queued_transfer(spi, msg, true);
+}
+
+static int spi_master_initialize_queue(struct spi_master *master)
+{
+	int ret;
+
+	master->transfer = spi_queued_transfer;
+	if (!master->transfer_one_message)
+		master->transfer_one_message = spi_transfer_one_message;
+
+	/* Initialize and start queue */
+	ret = spi_init_queue(master);
+	if (ret) {
+		dev_err(&master->dev, "problem initializing queue\n");
+		goto err_init_queue;
+	}
+	master->queued = true;
+	ret = spi_start_queue(master);
+	if (ret) {
+		dev_err(&master->dev, "problem starting queue\n");
+		goto err_start_queue;
+	}
+
+	return 0;
+
+err_start_queue:
+	spi_destroy_queue(master);
+err_init_queue:
+	return ret;
+}
+
+/*-------------------------------------------------------------------------*/
+
+#if defined(CONFIG_OF)
+static struct spi_device *
+of_register_spi_device(struct spi_master *master, struct device_node *nc)
+{
+	struct spi_device *spi;
+	int rc;
+	u32 value;
+
+	/* Alloc an spi_device */
+	spi = spi_alloc_device(master);
+	if (!spi) {
+		dev_err(&master->dev, "spi_device alloc error for %s\n",
+			nc->full_name);
+		rc = -ENOMEM;
+		goto err_out;
+	}
+
+	/* Select device driver */
+	rc = of_modalias_node(nc, spi->modalias,
+				sizeof(spi->modalias));
+	if (rc < 0) {
+		dev_err(&master->dev, "cannot find modalias for %s\n",
+			nc->full_name);
+		goto err_out;
+	}
+
+	/* Device address */
+	rc = of_property_read_u32(nc, "reg", &value);
+	if (rc) {
+		dev_err(&master->dev, "%s has no valid 'reg' property (%d)\n",
+			nc->full_name, rc);
+		goto err_out;
+	}
+	spi->chip_select = value;
+
+	/* Mode (clock phase/polarity/etc.) */
+	if (of_find_property(nc, "spi-cpha", NULL))
+		spi->mode |= SPI_CPHA;
+	if (of_find_property(nc, "spi-cpol", NULL))
+		spi->mode |= SPI_CPOL;
+	if (of_find_property(nc, "spi-cs-high", NULL))
+		spi->mode |= SPI_CS_HIGH;
+	if (of_find_property(nc, "spi-3wire", NULL))
+		spi->mode |= SPI_3WIRE;
+	if (of_find_property(nc, "spi-lsb-first", NULL))
+		spi->mode |= SPI_LSB_FIRST;
+
+	/* Device DUAL/QUAD mode */
+	if (!of_property_read_u32(nc, "spi-tx-bus-width", &value)) {
+		switch (value) {
+		case 1:
+			break;
+		case 2:
+			spi->mode |= SPI_TX_DUAL;
+			break;
+		case 4:
+			spi->mode |= SPI_TX_QUAD;
+			break;
+		default:
+			dev_warn(&master->dev,
+				"spi-tx-bus-width %d not supported\n",
+				value);
+			break;
+		}
+	}
+
+	if (!of_property_read_u32(nc, "spi-rx-bus-width", &value)) {
+		switch (value) {
+		case 1:
+			break;
+		case 2:
+			spi->mode |= SPI_RX_DUAL;
+			break;
+		case 4:
+			spi->mode |= SPI_RX_QUAD;
+			break;
+		default:
+			dev_warn(&master->dev,
+				"spi-rx-bus-width %d not supported\n",
+				value);
+			break;
+		}
+	}
+
+	/* Device speed */
+	rc = of_property_read_u32(nc, "spi-max-frequency", &value);
+	if (rc) {
+		dev_err(&master->dev, "%s has no valid 'spi-max-frequency' property (%d)\n",
+			nc->full_name, rc);
+		goto err_out;
+	}
+	spi->max_speed_hz = value;
+
+	/* IRQ */
+	spi->irq = irq_of_parse_and_map(nc, 0);
+
+	/* Store a pointer to the node in the device structure */
+	of_node_get(nc);
+	spi->dev.of_node = nc;
+
+	/* Register the new device */
+	rc = spi_add_device(spi);
+	if (rc) {
+		dev_err(&master->dev, "spi_device register error %s\n",
+			nc->full_name);
+		goto err_out;
+	}
+
+	return spi;
+
+err_out:
+	spi_dev_put(spi);
+	return ERR_PTR(rc);
+}
+
+/**
+ * of_register_spi_devices() - Register child devices onto the SPI bus
+ * @master:	Pointer to spi_master device
+ *
+ * Registers an spi_device for each child node of master node which has a 'reg'
+ * property.
+ */
+static void of_register_spi_devices(struct spi_master *master)
+{
+	struct spi_device *spi;
+	struct device_node *nc;
+
+	if (!master->dev.of_node)
+		return;
+
+	for_each_available_child_of_node(master->dev.of_node, nc) {
+		spi = of_register_spi_device(master, nc);
+		if (IS_ERR(spi))
+			dev_warn(&master->dev, "Failed to create SPI device for %s\n",
+				nc->full_name);
+	}
+}
+#else
+static void of_register_spi_devices(struct spi_master *master) { }
+#endif
+
+#ifdef CONFIG_ACPI
+static int acpi_spi_add_resource(struct acpi_resource *ares, void *data)
+{
+	struct spi_device *spi = data;
+
+	if (ares->type == ACPI_RESOURCE_TYPE_SERIAL_BUS) {
+		struct acpi_resource_spi_serialbus *sb;
+
+		sb = &ares->data.spi_serial_bus;
+		if (sb->type == ACPI_RESOURCE_SERIAL_TYPE_SPI) {
+			spi->chip_select = sb->device_selection;
+			spi->max_speed_hz = sb->connection_speed;
+
+			if (sb->clock_phase == ACPI_SPI_SECOND_PHASE)
+				spi->mode |= SPI_CPHA;
+			if (sb->clock_polarity == ACPI_SPI_START_HIGH)
+				spi->mode |= SPI_CPOL;
+			if (sb->device_polarity == ACPI_SPI_ACTIVE_HIGH)
+				spi->mode |= SPI_CS_HIGH;
+		}
+	} else if (spi->irq < 0) {
+		struct resource r;
+
+		if (acpi_dev_resource_interrupt(ares, 0, &r))
+			spi->irq = r.start;
+	}
+
+	/* Always tell the ACPI core to skip this resource */
+	return 1;
+}
+
+static acpi_status acpi_spi_add_device(acpi_handle handle, u32 level,
+				       void *data, void **return_value)
+{
+	struct spi_master *master = data;
+	struct list_head resource_list;
+	struct acpi_device *adev;
+	struct spi_device *spi;
+	int ret;
+
+	if (acpi_bus_get_device(handle, &adev))
+		return AE_OK;
+	if (acpi_bus_get_status(adev) || !adev->status.present)
+		return AE_OK;
+
+	spi = spi_alloc_device(master);
+	if (!spi) {
+		dev_err(&master->dev, "failed to allocate SPI device for %s\n",
+			dev_name(&adev->dev));
+		return AE_NO_MEMORY;
+	}
+
+	ACPI_COMPANION_SET(&spi->dev, adev);
+	spi->irq = -1;
+
+	INIT_LIST_HEAD(&resource_list);
+	ret = acpi_dev_get_resources(adev, &resource_list,
+				     acpi_spi_add_resource, spi);
+	acpi_dev_free_resource_list(&resource_list);
+
+	if (ret < 0 || !spi->max_speed_hz) {
+		spi_dev_put(spi);
+		return AE_OK;
+	}
+
+	adev->power.flags.ignore_parent = true;
+	strlcpy(spi->modalias, acpi_device_hid(adev), sizeof(spi->modalias));
+	if (spi_add_device(spi)) {
+		adev->power.flags.ignore_parent = false;
+		dev_err(&master->dev, "failed to add SPI device %s from ACPI\n",
+			dev_name(&adev->dev));
+		spi_dev_put(spi);
+	}
+
+	return AE_OK;
+}
+
+static void acpi_register_spi_devices(struct spi_master *master)
+{
+	acpi_status status;
+	acpi_handle handle;
+
+	handle = ACPI_HANDLE(master->dev.parent);
+	if (!handle)
+		return;
+
+	status = acpi_walk_namespace(ACPI_TYPE_DEVICE, handle, 1,
+				     acpi_spi_add_device, NULL,
+				     master, NULL);
+	if (ACPI_FAILURE(status))
+		dev_warn(&master->dev, "failed to enumerate SPI slaves\n");
+}
+#else
+static inline void acpi_register_spi_devices(struct spi_master *master) {}
+#endif /* CONFIG_ACPI */
+
+static void spi_master_release(struct device *dev)
+{
+	struct spi_master *master;
+
+	master = container_of(dev, struct spi_master, dev);
+	kfree(master);
+}
+
+static struct class spi_master_class = {
+	.name		= "spi_master",
+	.owner		= THIS_MODULE,
+	.dev_release	= spi_master_release,
+};
+
+
+
+/**
+ * spi_alloc_master - allocate SPI master controller
+ * @dev: the controller, possibly using the platform_bus
+ * @size: how much zeroed driver-private data to allocate; the pointer to this
+ *	memory is in the driver_data field of the returned device,
+ *	accessible with spi_master_get_devdata().
+ * Context: can sleep
+ *
+ * This call is used only by SPI master controller drivers, which are the
+ * only ones directly touching chip registers.  It's how they allocate
+ * an spi_master structure, prior to calling spi_register_master().
+ *
+ * This must be called from context that can sleep.  It returns the SPI
+ * master structure on success, else NULL.
+ *
+ * The caller is responsible for assigning the bus number and initializing
+ * the master's methods before calling spi_register_master(); and (after errors
+ * adding the device) calling spi_master_put() and kfree() to prevent a memory
+ * leak.
+ */
+struct spi_master *spi_alloc_master(struct device *dev, unsigned size)
+{
+	struct spi_master	*master;
+
+	if (!dev)
+		return NULL;
+
+	master = kzalloc(size + sizeof(*master), GFP_KERNEL);
+	if (!master)
+		return NULL;
+
+	device_initialize(&master->dev);
+	master->bus_num = -1;
+	master->num_chipselect = 1;
+	master->dev.class = &spi_master_class;
+	master->dev.parent = get_device(dev);
+	spi_master_set_devdata(master, &master[1]);
+
+	return master;
+}
+EXPORT_SYMBOL_GPL(spi_alloc_master);
+
+#ifdef CONFIG_OF
+static int of_spi_register_master(struct spi_master *master)
+{
+	int nb, i, *cs;
+	struct device_node *np = master->dev.of_node;
+
+	if (!np)
+		return 0;
+
+	nb = of_gpio_named_count(np, "cs-gpios");
+	master->num_chipselect = max_t(int, nb, master->num_chipselect);
+
+	/* Return error only for an incorrectly formed cs-gpios property */
+	if (nb == 0 || nb == -ENOENT)
+		return 0;
+	else if (nb < 0)
+		return nb;
+
+	cs = devm_kzalloc(&master->dev,
+			  sizeof(int) * master->num_chipselect,
+			  GFP_KERNEL);
+	master->cs_gpios = cs;
+
+	if (!master->cs_gpios)
+		return -ENOMEM;
+
+	for (i = 0; i < master->num_chipselect; i++)
+		cs[i] = -ENOENT;
+
+	for (i = 0; i < nb; i++)
+		cs[i] = of_get_named_gpio(np, "cs-gpios", i);
+
+	return 0;
+}
+#else
+static int of_spi_register_master(struct spi_master *master)
+{
+	return 0;
+}
+#endif
+
+/**
+ * spi_register_master - register SPI master controller
+ * @master: initialized master, originally from spi_alloc_master()
+ * Context: can sleep
+ *
+ * SPI master controllers connect to their drivers using some non-SPI bus,
+ * such as the platform bus.  The final stage of probe() in that code
+ * includes calling spi_register_master() to hook up to this SPI bus glue.
+ *
+ * SPI controllers use board specific (often SOC specific) bus numbers,
+ * and board-specific addressing for SPI devices combines those numbers
+ * with chip select numbers.  Since SPI does not directly support dynamic
+ * device identification, boards need configuration tables telling which
+ * chip is at which address.
+ *
+ * This must be called from context that can sleep.  It returns zero on
+ * success, else a negative error code (dropping the master's refcount).
+ * After a successful return, the caller is responsible for calling
+ * spi_unregister_master().
+ */
+int spi_register_master(struct spi_master *master)
+{
+	static atomic_t		dyn_bus_id = ATOMIC_INIT((1<<15) - 1);
+	struct device		*dev = master->dev.parent;
+	struct boardinfo	*bi;
+	int			status = -ENODEV;
+	int			dynamic = 0;
+
+	if (!dev)
+		return -ENODEV;
+
+	status = of_spi_register_master(master);
+	if (status)
+		return status;
+
+	/* even if it's just one always-selected device, there must
+	 * be at least one chipselect
+	 */
+	if (master->num_chipselect == 0)
+		return -EINVAL;
+
+	if ((master->bus_num < 0) && master->dev.of_node)
+		master->bus_num = of_alias_get_id(master->dev.of_node, "spi");
+
+	/* convention:  dynamically assigned bus IDs count down from the max */
+	if (master->bus_num < 0) {
+		/* FIXME switch to an IDR based scheme, something like
+		 * I2C now uses, so we can't run out of "dynamic" IDs
+		 */
+		master->bus_num = atomic_dec_return(&dyn_bus_id);
+		dynamic = 1;
+	}
+
+	INIT_LIST_HEAD(&master->queue);
+	spin_lock_init(&master->queue_lock);
+	spin_lock_init(&master->bus_lock_spinlock);
+	mutex_init(&master->bus_lock_mutex);
+	master->bus_lock_flag = 0;
+	init_completion(&master->xfer_completion);
+	if (!master->max_dma_len)
+		master->max_dma_len = INT_MAX;
+
+	/* register the device, then userspace will see it.
+	 * registration fails if the bus ID is in use.
+	 */
+	dev_set_name(&master->dev, "spi%u", master->bus_num);
+	status = device_add(&master->dev);
+	if (status < 0)
+		goto done;
+	dev_dbg(dev, "registered master %s%s\n", dev_name(&master->dev),
+			dynamic ? " (dynamic)" : "");
+
+	/* If we're using a queued driver, start the queue */
+	if (master->transfer)
+		dev_info(dev, "master is unqueued, this is deprecated\n");
+	else {
+		status = spi_master_initialize_queue(master);
+		if (status) {
+			device_del(&master->dev);
+			goto done;
+		}
+	}
+
+	mutex_lock(&board_lock);
+	list_add_tail(&master->list, &spi_master_list);
+	list_for_each_entry(bi, &board_list, list)
+		spi_match_master_to_boardinfo(master, &bi->board_info);
+	mutex_unlock(&board_lock);
+
+	/* Register devices from the device tree and ACPI */
+	of_register_spi_devices(master);
+	acpi_register_spi_devices(master);
+done:
+	return status;
+}
+EXPORT_SYMBOL_GPL(spi_register_master);
+
+static void devm_spi_unregister(struct device *dev, void *res)
+{
+	spi_unregister_master(*(struct spi_master **)res);
+}
+
+/**
+ * dev_spi_register_master - register managed SPI master controller
+ * @dev:    device managing SPI master
+ * @master: initialized master, originally from spi_alloc_master()
+ * Context: can sleep
+ *
+ * Register a SPI device as with spi_register_master() which will
+ * automatically be unregister
+ */
+int devm_spi_register_master(struct device *dev, struct spi_master *master)
+{
+	struct spi_master **ptr;
+	int ret;
+
+	ptr = devres_alloc(devm_spi_unregister, sizeof(*ptr), GFP_KERNEL);
+	if (!ptr)
+		return -ENOMEM;
+
+	ret = spi_register_master(master);
+	if (!ret) {
+		*ptr = master;
+		devres_add(dev, ptr);
+	} else {
+		devres_free(ptr);
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(devm_spi_register_master);
+
+static int __unregister(struct device *dev, void *null)
+{
+	spi_unregister_device(to_spi_device(dev));
+	return 0;
+}
+
+/**
+ * spi_unregister_master - unregister SPI master controller
+ * @master: the master being unregistered
+ * Context: can sleep
+ *
+ * This call is used only by SPI master controller drivers, which are the
+ * only ones directly touching chip registers.
+ *
+ * This must be called from context that can sleep.
+ */
+void spi_unregister_master(struct spi_master *master)
+{
+	int dummy;
+
+	if (master->queued) {
+		if (spi_destroy_queue(master))
+			dev_err(&master->dev, "queue remove failed\n");
+	}
+
+	mutex_lock(&board_lock);
+	list_del(&master->list);
+	mutex_unlock(&board_lock);
+
+	dummy = device_for_each_child(&master->dev, NULL, __unregister);
+	device_unregister(&master->dev);
+}
+EXPORT_SYMBOL_GPL(spi_unregister_master);
+
+int spi_master_suspend(struct spi_master *master)
+{
+	int ret;
+
+	/* Basically no-ops for non-queued masters */
+	if (!master->queued)
+		return 0;
+
+	ret = spi_stop_queue(master);
+	if (ret)
+		dev_err(&master->dev, "queue stop failed\n");
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(spi_master_suspend);
+
+int spi_master_resume(struct spi_master *master)
+{
+	int ret;
+
+	if (!master->queued)
+		return 0;
+
+	ret = spi_start_queue(master);
+	if (ret)
+		dev_err(&master->dev, "queue restart failed\n");
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(spi_master_resume);
+
+static int __spi_master_match(struct device *dev, const void *data)
+{
+	struct spi_master *m;
+	const u16 *bus_num = data;
+
+	m = container_of(dev, struct spi_master, dev);
+	return m->bus_num == *bus_num;
+}
+
+/**
+ * spi_busnum_to_master - look up master associated with bus_num
+ * @bus_num: the master's bus number
+ * Context: can sleep
+ *
+ * This call may be used with devices that are registered after
+ * arch init time.  It returns a refcounted pointer to the relevant
+ * spi_master (which the caller must release), or NULL if there is
+ * no such master registered.
+ */
+struct spi_master *spi_busnum_to_master(u16 bus_num)
+{
+	struct device		*dev;
+	struct spi_master	*master = NULL;
+
+	dev = class_find_device(&spi_master_class, NULL, &bus_num,
+				__spi_master_match);
+	if (dev)
+		master = container_of(dev, struct spi_master, dev);
+	/* reference got in class_find_device */
+	return master;
+}
+EXPORT_SYMBOL_GPL(spi_busnum_to_master);
+
+
+/*-------------------------------------------------------------------------*/
+
+/* Core methods for SPI master protocol drivers.  Some of the
+ * other core methods are currently defined as inline functions.
+ */
+
+/**
+ * spi_setup - setup SPI mode and clock rate
+ * @spi: the device whose settings are being modified
+ * Context: can sleep, and no requests are queued to the device
+ *
+ * SPI protocol drivers may need to update the transfer mode if the
+ * device doesn't work with its default.  They may likewise need
+ * to update clock rates or word sizes from initial values.  This function
+ * changes those settings, and must be called from a context that can sleep.
+ * Except for SPI_CS_HIGH, which takes effect immediately, the changes take
+ * effect the next time the device is selected and data is transferred to
+ * or from it.  When this function returns, the spi device is deselected.
+ *
+ * Note that this call will fail if the protocol driver specifies an option
+ * that the underlying controller or its driver does not support.  For
+ * example, not all hardware supports wire transfers using nine bit words,
+ * LSB-first wire encoding, or active-high chipselects.
+ */
+int spi_setup(struct spi_device *spi)
+{
+	unsigned	bad_bits, ugly_bits;
+	int		status = 0;
+
+	/* check mode to prevent that DUAL and QUAD set at the same time
+	 */
+	if (((spi->mode & SPI_TX_DUAL) && (spi->mode & SPI_TX_QUAD)) ||
+		((spi->mode & SPI_RX_DUAL) && (spi->mode & SPI_RX_QUAD))) {
+		dev_err(&spi->dev,
+		"setup: can not select dual and quad at the same time\n");
+		return -EINVAL;
+	}
+	/* if it is SPI_3WIRE mode, DUAL and QUAD should be forbidden
+	 */
+	if ((spi->mode & SPI_3WIRE) && (spi->mode &
+		(SPI_TX_DUAL | SPI_TX_QUAD | SPI_RX_DUAL | SPI_RX_QUAD)))
+		return -EINVAL;
+	/* help drivers fail *cleanly* when they need options
+	 * that aren't supported with their current master
+	 */
+	bad_bits = spi->mode & ~spi->master->mode_bits;
+	ugly_bits = bad_bits &
+		    (SPI_TX_DUAL | SPI_TX_QUAD | SPI_RX_DUAL | SPI_RX_QUAD);
+	if (ugly_bits) {
+		dev_warn(&spi->dev,
+			 "setup: ignoring unsupported mode bits %x\n",
+			 ugly_bits);
+		spi->mode &= ~ugly_bits;
+		bad_bits &= ~ugly_bits;
+	}
+	if (bad_bits) {
+		dev_err(&spi->dev, "setup: unsupported mode bits %x\n",
+			bad_bits);
+		return -EINVAL;
+	}
+
+	if (!spi->bits_per_word)
+		spi->bits_per_word = 8;
+
+	if (!spi->max_speed_hz)
+		spi->max_speed_hz = spi->master->max_speed_hz;
+
+	spi_set_cs(spi, false);
+
+	if (spi->master->setup)
+		status = spi->master->setup(spi);
+
+	dev_dbg(&spi->dev, "setup mode %d, %s%s%s%s%u bits/w, %u Hz max --> %d\n",
+			(int) (spi->mode & (SPI_CPOL | SPI_CPHA)),
+			(spi->mode & SPI_CS_HIGH) ? "cs_high, " : "",
+			(spi->mode & SPI_LSB_FIRST) ? "lsb, " : "",
+			(spi->mode & SPI_3WIRE) ? "3wire, " : "",
+			(spi->mode & SPI_LOOP) ? "loopback, " : "",
+			spi->bits_per_word, spi->max_speed_hz,
+			status);
+
+	return status;
+}
+EXPORT_SYMBOL_GPL(spi_setup);
+
+static int __spi_validate(struct spi_device *spi, struct spi_message *message)
+{
+	struct spi_master *master = spi->master;
+	struct spi_transfer *xfer;
+	int w_size;
+
+	if (list_empty(&message->transfers))
+		return -EINVAL;
+
+	/* Half-duplex links include original MicroWire, and ones with
+	 * only one data pin like SPI_3WIRE (switches direction) or where
+	 * either MOSI or MISO is missing.  They can also be caused by
+	 * software limitations.
+	 */
+	if ((master->flags & SPI_MASTER_HALF_DUPLEX)
+			|| (spi->mode & SPI_3WIRE)) {
+		unsigned flags = master->flags;
+
+		list_for_each_entry(xfer, &message->transfers, transfer_list) {
+			if (xfer->rx_buf && xfer->tx_buf)
+				return -EINVAL;
+			if ((flags & SPI_MASTER_NO_TX) && xfer->tx_buf)
+				return -EINVAL;
+			if ((flags & SPI_MASTER_NO_RX) && xfer->rx_buf)
+				return -EINVAL;
+		}
+	}
+
+	/**
+	 * Set transfer bits_per_word and max speed as spi device default if
+	 * it is not set for this transfer.
+	 * Set transfer tx_nbits and rx_nbits as single transfer default
+	 * (SPI_NBITS_SINGLE) if it is not set for this transfer.
+	 */
+	list_for_each_entry(xfer, &message->transfers, transfer_list) {
+		message->frame_length += xfer->len;
+		if (!xfer->bits_per_word)
+			xfer->bits_per_word = spi->bits_per_word;
+
+		if (!xfer->speed_hz)
+			xfer->speed_hz = spi->max_speed_hz;
+
+		if (master->max_speed_hz &&
+		    xfer->speed_hz > master->max_speed_hz)
+			xfer->speed_hz = master->max_speed_hz;
+
+		if (master->bits_per_word_mask) {
+			/* Only 32 bits fit in the mask */
+			if (xfer->bits_per_word > 32)
+				return -EINVAL;
+			if (!(master->bits_per_word_mask &
+					BIT(xfer->bits_per_word - 1)))
+				return -EINVAL;
+		}
+
+		/*
+		 * SPI transfer length should be multiple of SPI word size
+		 * where SPI word size should be power-of-two multiple
+		 */
+		if (xfer->bits_per_word <= 8)
+			w_size = 1;
+		else if (xfer->bits_per_word <= 16)
+			w_size = 2;
+		else
+			w_size = 4;
+
+		/* No partial transfers accepted */
+		if (xfer->len % w_size)
+			return -EINVAL;
+
+		if (xfer->speed_hz && master->min_speed_hz &&
+		    xfer->speed_hz < master->min_speed_hz)
+			return -EINVAL;
+
+		if (xfer->tx_buf && !xfer->tx_nbits)
+			xfer->tx_nbits = SPI_NBITS_SINGLE;
+		if (xfer->rx_buf && !xfer->rx_nbits)
+			xfer->rx_nbits = SPI_NBITS_SINGLE;
+		/* check transfer tx/rx_nbits:
+		 * 1. check the value matches one of single, dual and quad
+		 * 2. check tx/rx_nbits match the mode in spi_device
+		 */
+		if (xfer->tx_buf) {
+			if (xfer->tx_nbits != SPI_NBITS_SINGLE &&
+				xfer->tx_nbits != SPI_NBITS_DUAL &&
+				xfer->tx_nbits != SPI_NBITS_QUAD)
+				return -EINVAL;
+			if ((xfer->tx_nbits == SPI_NBITS_DUAL) &&
+				!(spi->mode & (SPI_TX_DUAL | SPI_TX_QUAD)))
+				return -EINVAL;
+			if ((xfer->tx_nbits == SPI_NBITS_QUAD) &&
+				!(spi->mode & SPI_TX_QUAD))
+				return -EINVAL;
+		}
+		/* check transfer rx_nbits */
+		if (xfer->rx_buf) {
+			if (xfer->rx_nbits != SPI_NBITS_SINGLE &&
+				xfer->rx_nbits != SPI_NBITS_DUAL &&
+				xfer->rx_nbits != SPI_NBITS_QUAD)
+				return -EINVAL;
+			if ((xfer->rx_nbits == SPI_NBITS_DUAL) &&
+				!(spi->mode & (SPI_RX_DUAL | SPI_RX_QUAD)))
+				return -EINVAL;
+			if ((xfer->rx_nbits == SPI_NBITS_QUAD) &&
+				!(spi->mode & SPI_RX_QUAD))
+				return -EINVAL;
+		}
+	}
+
+	message->status = -EINPROGRESS;
+
+	return 0;
+}
+
+static int __spi_async(struct spi_device *spi, struct spi_message *message)
+{
+	struct spi_master *master = spi->master;
+
+	message->spi = spi;
+
+	trace_spi_message_submit(message);
+
+	return master->transfer(spi, message);
+}
+
+/**
+ * spi_async - asynchronous SPI transfer
+ * @spi: device with which data will be exchanged
+ * @message: describes the data transfers, including completion callback
+ * Context: any (irqs may be blocked, etc)
+ *
+ * This call may be used in_irq and other contexts which can't sleep,
+ * as well as from task contexts which can sleep.
+ *
+ * The completion callback is invoked in a context which can't sleep.
+ * Before that invocation, the value of message->status is undefined.
+ * When the callback is issued, message->status holds either zero (to
+ * indicate complete success) or a negative error code.  After that
+ * callback returns, the driver which issued the transfer request may
+ * deallocate the associated memory; it's no longer in use by any SPI
+ * core or controller driver code.
+ *
+ * Note that although all messages to a spi_device are handled in
+ * FIFO order, messages may go to different devices in other orders.
+ * Some device might be higher priority, or have various "hard" access
+ * time requirements, for example.
+ *
+ * On detection of any fault during the transfer, processing of
+ * the entire message is aborted, and the device is deselected.
+ * Until returning from the associated message completion callback,
+ * no other spi_message queued to that device will be processed.
+ * (This rule applies equally to all the synchronous transfer calls,
+ * which are wrappers around this core asynchronous primitive.)
+ */
+int spi_async(struct spi_device *spi, struct spi_message *message)
+{
+	struct spi_master *master = spi->master;
+	int ret;
+	unsigned long flags;
+
+	ret = __spi_validate(spi, message);
+	if (ret != 0)
+		return ret;
+
+	spin_lock_irqsave(&master->bus_lock_spinlock, flags);
+
+	if (master->bus_lock_flag)
+		ret = -EBUSY;
+	else
+		ret = __spi_async(spi, message);
+
+	spin_unlock_irqrestore(&master->bus_lock_spinlock, flags);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(spi_async);
+
+/**
+ * spi_async_locked - version of spi_async with exclusive bus usage
+ * @spi: device with which data will be exchanged
+ * @message: describes the data transfers, including completion callback
+ * Context: any (irqs may be blocked, etc)
+ *
+ * This call may be used in_irq and other contexts which can't sleep,
+ * as well as from task contexts which can sleep.
+ *
+ * The completion callback is invoked in a context which can't sleep.
+ * Before that invocation, the value of message->status is undefined.
+ * When the callback is issued, message->status holds either zero (to
+ * indicate complete success) or a negative error code.  After that
+ * callback returns, the driver which issued the transfer request may
+ * deallocate the associated memory; it's no longer in use by any SPI
+ * core or controller driver code.
+ *
+ * Note that although all messages to a spi_device are handled in
+ * FIFO order, messages may go to different devices in other orders.
+ * Some device might be higher priority, or have various "hard" access
+ * time requirements, for example.
+ *
+ * On detection of any fault during the transfer, processing of
+ * the entire message is aborted, and the device is deselected.
+ * Until returning from the associated message completion callback,
+ * no other spi_message queued to that device will be processed.
+ * (This rule applies equally to all the synchronous transfer calls,
+ * which are wrappers around this core asynchronous primitive.)
+ */
+int spi_async_locked(struct spi_device *spi, struct spi_message *message)
+{
+	struct spi_master *master = spi->master;
+	int ret;
+	unsigned long flags;
+
+	ret = __spi_validate(spi, message);
+	if (ret != 0)
+		return ret;
+
+	spin_lock_irqsave(&master->bus_lock_spinlock, flags);
+
+	ret = __spi_async(spi, message);
+
+	spin_unlock_irqrestore(&master->bus_lock_spinlock, flags);
+
+	return ret;
+
+}
+EXPORT_SYMBOL_GPL(spi_async_locked);
+
+
+/*-------------------------------------------------------------------------*/
+
+/* Utility methods for SPI master protocol drivers, layered on
+ * top of the core.  Some other utility methods are defined as
+ * inline functions.
+ */
+
+static void spi_complete(void *arg)
+{
+	complete(arg);
+}
+
+static int __spi_sync(struct spi_device *spi, struct spi_message *message,
+		      int bus_locked)
+{
+	DECLARE_COMPLETION_ONSTACK(done);
+	int status;
+	struct spi_master *master = spi->master;
+	unsigned long flags;
+
+	status = __spi_validate(spi, message);
+	if (status != 0)
+		return status;
+
+	message->complete = spi_complete;
+	message->context = &done;
+	message->spi = spi;
+
+	if (!bus_locked)
+		mutex_lock(&master->bus_lock_mutex);
+
+	/* If we're not using the legacy transfer method then we will
+	 * try to transfer in the calling context so special case.
+	 * This code would be less tricky if we could remove the
+	 * support for driver implemented message queues.
+	 */
+	if (master->transfer == spi_queued_transfer) {
+		spin_lock_irqsave(&master->bus_lock_spinlock, flags);
+
+		trace_spi_message_submit(message);
+
+		status = __spi_queued_transfer(spi, message, false);
+
+		spin_unlock_irqrestore(&master->bus_lock_spinlock, flags);
+	} else {
+		status = spi_async_locked(spi, message);
+	}
+
+	if (!bus_locked)
+		mutex_unlock(&master->bus_lock_mutex);
+
+	if (status == 0) {
+		/* Push out the messages in the calling context if we
+		 * can.
+		 */
+		if (master->transfer == spi_queued_transfer)
+			__spi_pump_messages(master, false);
+
+		wait_for_completion(&done);
+		status = message->status;
+	}
+	message->context = NULL;
+	return status;
+}
+
+/**
+ * spi_sync - blocking/synchronous SPI data transfers
+ * @spi: device with which data will be exchanged
+ * @message: describes the data transfers
+ * Context: can sleep
+ *
+ * This call may only be used from a context that may sleep.  The sleep
+ * is non-interruptible, and has no timeout.  Low-overhead controller
+ * drivers may DMA directly into and out of the message buffers.
+ *
+ * Note that the SPI device's chip select is active during the message,
+ * and then is normally disabled between messages.  Drivers for some
+ * frequently-used devices may want to minimize costs of selecting a chip,
+ * by leaving it selected in anticipation that the next message will go
+ * to the same chip.  (That may increase power usage.)
+ *
+ * Also, the caller is guaranteeing that the memory associated with the
+ * message will not be freed before this call returns.
+ *
+ * It returns zero on success, else a negative error code.
+ */
+int spi_sync(struct spi_device *spi, struct spi_message *message)
+{
+	return __spi_sync(spi, message, 0);
+}
+EXPORT_SYMBOL_GPL(spi_sync);
+
+/**
+ * spi_sync_locked - version of spi_sync with exclusive bus usage
+ * @spi: device with which data will be exchanged
+ * @message: describes the data transfers
+ * Context: can sleep
+ *
+ * This call may only be used from a context that may sleep.  The sleep
+ * is non-interruptible, and has no timeout.  Low-overhead controller
+ * drivers may DMA directly into and out of the message buffers.
+ *
+ * This call should be used by drivers that require exclusive access to the
+ * SPI bus. It has to be preceded by a spi_bus_lock call. The SPI bus must
+ * be released by a spi_bus_unlock call when the exclusive access is over.
+ *
+ * It returns zero on success, else a negative error code.
+ */
+int spi_sync_locked(struct spi_device *spi, struct spi_message *message)
+{
+	return __spi_sync(spi, message, 1);
+}
+EXPORT_SYMBOL_GPL(spi_sync_locked);
+
+/**
+ * spi_bus_lock - obtain a lock for exclusive SPI bus usage
+ * @master: SPI bus master that should be locked for exclusive bus access
+ * Context: can sleep
+ *
+ * This call may only be used from a context that may sleep.  The sleep
+ * is non-interruptible, and has no timeout.
+ *
+ * This call should be used by drivers that require exclusive access to the
+ * SPI bus. The SPI bus must be released by a spi_bus_unlock call when the
+ * exclusive access is over. Data transfer must be done by spi_sync_locked
+ * and spi_async_locked calls when the SPI bus lock is held.
+ *
+ * It returns zero on success, else a negative error code.
+ */
+int spi_bus_lock(struct spi_master *master)
+{
+	unsigned long flags;
+
+	mutex_lock(&master->bus_lock_mutex);
+
+	spin_lock_irqsave(&master->bus_lock_spinlock, flags);
+	master->bus_lock_flag = 1;
+	spin_unlock_irqrestore(&master->bus_lock_spinlock, flags);
+
+	/* mutex remains locked until spi_bus_unlock is called */
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(spi_bus_lock);
+
+/**
+ * spi_bus_unlock - release the lock for exclusive SPI bus usage
+ * @master: SPI bus master that was locked for exclusive bus access
+ * Context: can sleep
+ *
+ * This call may only be used from a context that may sleep.  The sleep
+ * is non-interruptible, and has no timeout.
+ *
+ * This call releases an SPI bus lock previously obtained by an spi_bus_lock
+ * call.
+ *
+ * It returns zero on success, else a negative error code.
+ */
+int spi_bus_unlock(struct spi_master *master)
+{
+	master->bus_lock_flag = 0;
+
+	mutex_unlock(&master->bus_lock_mutex);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(spi_bus_unlock);
+
+/* portable code must never pass more than 32 bytes */
+#define	SPI_BUFSIZ	max(32, SMP_CACHE_BYTES)
+
+static u8	*buf;
+
+/**
+ * spi_write_then_read - SPI synchronous write followed by read
+ * @spi: device with which data will be exchanged
+ * @txbuf: data to be written (need not be dma-safe)
+ * @n_tx: size of txbuf, in bytes
+ * @rxbuf: buffer into which data will be read (need not be dma-safe)
+ * @n_rx: size of rxbuf, in bytes
+ * Context: can sleep
+ *
+ * This performs a half duplex MicroWire style transaction with the
+ * device, sending txbuf and then reading rxbuf.  The return value
+ * is zero for success, else a negative errno status code.
+ * This call may only be used from a context that may sleep.
+ *
+ * Parameters to this routine are always copied using a small buffer;
+ * portable code should never use this for more than 32 bytes.
+ * Performance-sensitive or bulk transfer code should instead use
+ * spi_{async,sync}() calls with dma-safe buffers.
+ */
+int spi_write_then_read(struct spi_device *spi,
+		const void *txbuf, unsigned n_tx,
+		void *rxbuf, unsigned n_rx)
+{
+	static DEFINE_MUTEX(lock);
+
+	int			status;
+	struct spi_message	message;
+	struct spi_transfer	x[2];
+	u8			*local_buf;
+
+	/* Use preallocated DMA-safe buffer if we can.  We can't avoid
+	 * copying here, (as a pure convenience thing), but we can
+	 * keep heap costs out of the hot path unless someone else is
+	 * using the pre-allocated buffer or the transfer is too large.
+	 */
+	if ((n_tx + n_rx) > SPI_BUFSIZ || !mutex_trylock(&lock)) {
+		local_buf = kmalloc(max((unsigned)SPI_BUFSIZ, n_tx + n_rx),
+				    GFP_KERNEL | GFP_DMA);
+		if (!local_buf)
+			return -ENOMEM;
+	} else {
+		local_buf = buf;
+	}
+
+	spi_message_init(&message);
+	memset(x, 0, sizeof(x));
+	if (n_tx) {
+		x[0].len = n_tx;
+		spi_message_add_tail(&x[0], &message);
+	}
+	if (n_rx) {
+		x[1].len = n_rx;
+		spi_message_add_tail(&x[1], &message);
+	}
+
+	memcpy(local_buf, txbuf, n_tx);
+	x[0].tx_buf = local_buf;
+	x[1].rx_buf = local_buf + n_tx;
+
+	/* do the i/o */
+	status = spi_sync(spi, &message);
+	if (status == 0)
+		memcpy(rxbuf, x[1].rx_buf, n_rx);
+
+	if (x[0].tx_buf == buf)
+		mutex_unlock(&lock);
+	else
+		kfree(local_buf);
+
+	return status;
+}
+EXPORT_SYMBOL_GPL(spi_write_then_read);
+
+/*-------------------------------------------------------------------------*/
+
+#if IS_ENABLED(CONFIG_OF_DYNAMIC)
+static int __spi_of_device_match(struct device *dev, void *data)
+{
+	return dev->of_node == data;
+}
+
+/* must call put_device() when done with returned spi_device device */
+static struct spi_device *of_find_spi_device_by_node(struct device_node *node)
+{
+	struct device *dev = bus_find_device(&spi_bus_type, NULL, node,
+						__spi_of_device_match);
+	return dev ? to_spi_device(dev) : NULL;
+}
+
+static int __spi_of_master_match(struct device *dev, const void *data)
+{
+	return dev->of_node == data;
+}
+
+/* the spi masters are not using spi_bus, so we find it with another way */
+static struct spi_master *of_find_spi_master_by_node(struct device_node *node)
+{
+	struct device *dev;
+
+	dev = class_find_device(&spi_master_class, NULL, node,
+				__spi_of_master_match);
+	if (!dev)
+		return NULL;
+
+	/* reference got in class_find_device */
+	return container_of(dev, struct spi_master, dev);
+}
+
+static int of_spi_notify(struct notifier_block *nb, unsigned long action,
+			 void *arg)
+{
+	struct of_reconfig_data *rd = arg;
+	struct spi_master *master;
+	struct spi_device *spi;
+
+	switch (of_reconfig_get_state_change(action, arg)) {
+	case OF_RECONFIG_CHANGE_ADD:
+		master = of_find_spi_master_by_node(rd->dn->parent);
+		if (master == NULL)
+			return NOTIFY_OK;	/* not for us */
+
+		spi = of_register_spi_device(master, rd->dn);
+		put_device(&master->dev);
+
+		if (IS_ERR(spi)) {
+			pr_err("%s: failed to create for '%s'\n",
+					__func__, rd->dn->full_name);
+			return notifier_from_errno(PTR_ERR(spi));
+		}
+		break;
+
+	case OF_RECONFIG_CHANGE_REMOVE:
+		/* find our device by node */
+		spi = of_find_spi_device_by_node(rd->dn);
+		if (spi == NULL)
+			return NOTIFY_OK;	/* no? not meant for us */
+
+		/* unregister takes one ref away */
+		spi_unregister_device(spi);
+
+		/* and put the reference of the find */
+		put_device(&spi->dev);
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block spi_of_notifier = {
+	.notifier_call = of_spi_notify,
+};
+#else /* IS_ENABLED(CONFIG_OF_DYNAMIC) */
+extern struct notifier_block spi_of_notifier;
+#endif /* IS_ENABLED(CONFIG_OF_DYNAMIC) */
+
+static int __init spi_init(void)
+{
+	int	status;
+
+	buf = kmalloc(SPI_BUFSIZ, GFP_KERNEL);
+	if (!buf) {
+		status = -ENOMEM;
+		goto err0;
+	}
+
+	status = bus_register(&spi_bus_type);
+	if (status < 0)
+		goto err1;
+
+	status = class_register(&spi_master_class);
+	if (status < 0)
+		goto err2;
+
+	if (IS_ENABLED(CONFIG_OF_DYNAMIC))
+		WARN_ON(of_reconfig_notifier_register(&spi_of_notifier));
+
+	return 0;
+
+err2:
+	bus_unregister(&spi_bus_type);
+err1:
+	kfree(buf);
+	buf = NULL;
+err0:
+	return status;
+}
+
+/* board_info is normally registered in arch_initcall(),
+ * but even essential drivers wait till later
+ *
+ * REVISIT only boardinfo really needs static linking. the rest (device and
+ * driver registration) _could_ be dynamically linked (modular) ... costs
+ * include needing to have boardinfo data structures be much more public.
+ */
+postcore_initcall(spi_init);
+