diff options
Diffstat (limited to 'drivers/spi/spi-gpio.c')
| -rw-r--r-- | drivers/spi/spi-gpio.c | 547 |
1 files changed, 547 insertions, 0 deletions
diff --git a/drivers/spi/spi-gpio.c b/drivers/spi/spi-gpio.c new file mode 100644 index 000000000..1c34c9314 --- /dev/null +++ b/drivers/spi/spi-gpio.c @@ -0,0 +1,547 @@ +/* + * SPI master driver using generic bitbanged GPIO + * + * Copyright (C) 2006,2008 David Brownell + * + * 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/module.h> +#include <linux/platform_device.h> +#include <linux/gpio.h> +#include <linux/of.h> +#include <linux/of_device.h> +#include <linux/of_gpio.h> + +#include <linux/spi/spi.h> +#include <linux/spi/spi_bitbang.h> +#include <linux/spi/spi_gpio.h> + + +/* + * This bitbanging SPI master driver should help make systems usable + * when a native hardware SPI engine is not available, perhaps because + * its driver isn't yet working or because the I/O pins it requires + * are used for other purposes. + * + * platform_device->driver_data ... points to spi_gpio + * + * spi->controller_state ... reserved for bitbang framework code + * spi->controller_data ... holds chipselect GPIO + * + * spi->master->dev.driver_data ... points to spi_gpio->bitbang + */ + +struct spi_gpio { + struct spi_bitbang bitbang; + struct spi_gpio_platform_data pdata; + struct platform_device *pdev; + unsigned long cs_gpios[0]; +}; + +/*----------------------------------------------------------------------*/ + +/* + * Because the overhead of going through four GPIO procedure calls + * per transferred bit can make performance a problem, this code + * is set up so that you can use it in either of two ways: + * + * - The slow generic way: set up platform_data to hold the GPIO + * numbers used for MISO/MOSI/SCK, and issue procedure calls for + * each of them. This driver can handle several such busses. + * + * - The quicker inlined way: only helps with platform GPIO code + * that inlines operations for constant GPIOs. This can give + * you tight (fast!) inner loops, but each such bus needs a + * new driver. You'll define a new C file, with Makefile and + * Kconfig support; the C code can be a total of six lines: + * + * #define DRIVER_NAME "myboard_spi2" + * #define SPI_MISO_GPIO 119 + * #define SPI_MOSI_GPIO 120 + * #define SPI_SCK_GPIO 121 + * #define SPI_N_CHIPSEL 4 + * #include "spi-gpio.c" + */ + +#ifndef DRIVER_NAME +#define DRIVER_NAME "spi_gpio" + +#define GENERIC_BITBANG /* vs tight inlines */ + +/* all functions referencing these symbols must define pdata */ +#define SPI_MISO_GPIO ((pdata)->miso) +#define SPI_MOSI_GPIO ((pdata)->mosi) +#define SPI_SCK_GPIO ((pdata)->sck) + +#define SPI_N_CHIPSEL ((pdata)->num_chipselect) + +#endif + +/*----------------------------------------------------------------------*/ + +static inline struct spi_gpio *__pure +spi_to_spi_gpio(const struct spi_device *spi) +{ + const struct spi_bitbang *bang; + struct spi_gpio *spi_gpio; + + bang = spi_master_get_devdata(spi->master); + spi_gpio = container_of(bang, struct spi_gpio, bitbang); + return spi_gpio; +} + +static inline struct spi_gpio_platform_data *__pure +spi_to_pdata(const struct spi_device *spi) +{ + return &spi_to_spi_gpio(spi)->pdata; +} + +/* this is #defined to avoid unused-variable warnings when inlining */ +#define pdata spi_to_pdata(spi) + +static inline void setsck(const struct spi_device *spi, int is_on) +{ + gpio_set_value_cansleep(SPI_SCK_GPIO, is_on); +} + +static inline void setmosi(const struct spi_device *spi, int is_on) +{ + gpio_set_value_cansleep(SPI_MOSI_GPIO, is_on); +} + +static inline int getmiso(const struct spi_device *spi) +{ + return !!gpio_get_value_cansleep(SPI_MISO_GPIO); +} + +#undef pdata + +/* + * NOTE: this clocks "as fast as we can". It "should" be a function of the + * requested device clock. Software overhead means we usually have trouble + * reaching even one Mbit/sec (except when we can inline bitops), so for now + * we'll just assume we never need additional per-bit slowdowns. + */ +#define spidelay(nsecs) do {} while (0) + +#include "spi-bitbang-txrx.h" + +/* + * These functions can leverage inline expansion of GPIO calls to shrink + * costs for a txrx bit, often by factors of around ten (by instruction + * count). That is particularly visible for larger word sizes, but helps + * even with default 8-bit words. + * + * REVISIT overheads calling these functions for each word also have + * significant performance costs. Having txrx_bufs() calls that inline + * the txrx_word() logic would help performance, e.g. on larger blocks + * used with flash storage or MMC/SD. There should also be ways to make + * GCC be less stupid about reloading registers inside the I/O loops, + * even without inlined GPIO calls; __attribute__((hot)) on GCC 4.3? + */ + +static u32 spi_gpio_txrx_word_mode0(struct spi_device *spi, + unsigned nsecs, u32 word, u8 bits) +{ + return bitbang_txrx_be_cpha0(spi, nsecs, 0, 0, word, bits); +} + +static u32 spi_gpio_txrx_word_mode1(struct spi_device *spi, + unsigned nsecs, u32 word, u8 bits) +{ + return bitbang_txrx_be_cpha1(spi, nsecs, 0, 0, word, bits); +} + +static u32 spi_gpio_txrx_word_mode2(struct spi_device *spi, + unsigned nsecs, u32 word, u8 bits) +{ + return bitbang_txrx_be_cpha0(spi, nsecs, 1, 0, word, bits); +} + +static u32 spi_gpio_txrx_word_mode3(struct spi_device *spi, + unsigned nsecs, u32 word, u8 bits) +{ + return bitbang_txrx_be_cpha1(spi, nsecs, 1, 0, word, bits); +} + +/* + * These functions do not call setmosi or getmiso if respective flag + * (SPI_MASTER_NO_RX or SPI_MASTER_NO_TX) is set, so they are safe to + * call when such pin is not present or defined in the controller. + * A separate set of callbacks is defined to get highest possible + * speed in the generic case (when both MISO and MOSI lines are + * available), as optimiser will remove the checks when argument is + * constant. + */ + +static u32 spi_gpio_spec_txrx_word_mode0(struct spi_device *spi, + unsigned nsecs, u32 word, u8 bits) +{ + unsigned flags = spi->master->flags; + return bitbang_txrx_be_cpha0(spi, nsecs, 0, flags, word, bits); +} + +static u32 spi_gpio_spec_txrx_word_mode1(struct spi_device *spi, + unsigned nsecs, u32 word, u8 bits) +{ + unsigned flags = spi->master->flags; + return bitbang_txrx_be_cpha1(spi, nsecs, 0, flags, word, bits); +} + +static u32 spi_gpio_spec_txrx_word_mode2(struct spi_device *spi, + unsigned nsecs, u32 word, u8 bits) +{ + unsigned flags = spi->master->flags; + return bitbang_txrx_be_cpha0(spi, nsecs, 1, flags, word, bits); +} + +static u32 spi_gpio_spec_txrx_word_mode3(struct spi_device *spi, + unsigned nsecs, u32 word, u8 bits) +{ + unsigned flags = spi->master->flags; + return bitbang_txrx_be_cpha1(spi, nsecs, 1, flags, word, bits); +} + +/*----------------------------------------------------------------------*/ + +static void spi_gpio_chipselect(struct spi_device *spi, int is_active) +{ + struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi); + unsigned long cs = spi_gpio->cs_gpios[spi->chip_select]; + + /* set initial clock polarity */ + if (is_active) + setsck(spi, spi->mode & SPI_CPOL); + + if (cs != SPI_GPIO_NO_CHIPSELECT) { + /* SPI is normally active-low */ + gpio_set_value_cansleep(cs, (spi->mode & SPI_CS_HIGH) ? is_active : !is_active); + } +} + +static int spi_gpio_setup(struct spi_device *spi) +{ + unsigned long cs; + int status = 0; + struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi); + struct device_node *np = spi->master->dev.of_node; + + if (np) { + /* + * In DT environments, the CS GPIOs have already been + * initialized from the "cs-gpios" property of the node. + */ + cs = spi_gpio->cs_gpios[spi->chip_select]; + } else { + /* + * ... otherwise, take it from spi->controller_data + */ + cs = (uintptr_t) spi->controller_data; + } + + if (!spi->controller_state) { + if (cs != SPI_GPIO_NO_CHIPSELECT) { + status = gpio_request(cs, dev_name(&spi->dev)); + if (status) + return status; + status = gpio_direction_output(cs, + !(spi->mode & SPI_CS_HIGH)); + } + } + if (!status) { + /* in case it was initialized from static board data */ + spi_gpio->cs_gpios[spi->chip_select] = cs; + status = spi_bitbang_setup(spi); + } + + if (status) { + if (!spi->controller_state && cs != SPI_GPIO_NO_CHIPSELECT) + gpio_free(cs); + } + return status; +} + +static void spi_gpio_cleanup(struct spi_device *spi) +{ + struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi); + unsigned long cs = spi_gpio->cs_gpios[spi->chip_select]; + + if (cs != SPI_GPIO_NO_CHIPSELECT) + gpio_free(cs); + spi_bitbang_cleanup(spi); +} + +static int spi_gpio_alloc(unsigned pin, const char *label, bool is_in) +{ + int value; + + value = gpio_request(pin, label); + if (value == 0) { + if (is_in) + value = gpio_direction_input(pin); + else + value = gpio_direction_output(pin, 0); + } + return value; +} + +static int spi_gpio_request(struct spi_gpio_platform_data *pdata, + const char *label, u16 *res_flags) +{ + int value; + + /* NOTE: SPI_*_GPIO symbols may reference "pdata" */ + + if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI) { + value = spi_gpio_alloc(SPI_MOSI_GPIO, label, false); + if (value) + goto done; + } else { + /* HW configuration without MOSI pin */ + *res_flags |= SPI_MASTER_NO_TX; + } + + if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO) { + value = spi_gpio_alloc(SPI_MISO_GPIO, label, true); + if (value) + goto free_mosi; + } else { + /* HW configuration without MISO pin */ + *res_flags |= SPI_MASTER_NO_RX; + } + + value = spi_gpio_alloc(SPI_SCK_GPIO, label, false); + if (value) + goto free_miso; + + goto done; + +free_miso: + if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO) + gpio_free(SPI_MISO_GPIO); +free_mosi: + if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI) + gpio_free(SPI_MOSI_GPIO); +done: + return value; +} + +#ifdef CONFIG_OF +static const struct of_device_id spi_gpio_dt_ids[] = { + { .compatible = "spi-gpio" }, + {} +}; +MODULE_DEVICE_TABLE(of, spi_gpio_dt_ids); + +static int spi_gpio_probe_dt(struct platform_device *pdev) +{ + int ret; + u32 tmp; + struct spi_gpio_platform_data *pdata; + struct device_node *np = pdev->dev.of_node; + const struct of_device_id *of_id = + of_match_device(spi_gpio_dt_ids, &pdev->dev); + + if (!of_id) + return 0; + + pdata = devm_kzalloc(&pdev->dev, sizeof(*pdata), GFP_KERNEL); + if (!pdata) + return -ENOMEM; + + ret = of_get_named_gpio(np, "gpio-sck", 0); + if (ret < 0) { + dev_err(&pdev->dev, "gpio-sck property not found\n"); + goto error_free; + } + pdata->sck = ret; + + ret = of_get_named_gpio(np, "gpio-miso", 0); + if (ret < 0) { + dev_info(&pdev->dev, "gpio-miso property not found, switching to no-rx mode\n"); + pdata->miso = SPI_GPIO_NO_MISO; + } else + pdata->miso = ret; + + ret = of_get_named_gpio(np, "gpio-mosi", 0); + if (ret < 0) { + dev_info(&pdev->dev, "gpio-mosi property not found, switching to no-tx mode\n"); + pdata->mosi = SPI_GPIO_NO_MOSI; + } else + pdata->mosi = ret; + + ret = of_property_read_u32(np, "num-chipselects", &tmp); + if (ret < 0) { + dev_err(&pdev->dev, "num-chipselects property not found\n"); + goto error_free; + } + + pdata->num_chipselect = tmp; + pdev->dev.platform_data = pdata; + + return 1; + +error_free: + devm_kfree(&pdev->dev, pdata); + return ret; +} +#else +static inline int spi_gpio_probe_dt(struct platform_device *pdev) +{ + return 0; +} +#endif + +static int spi_gpio_probe(struct platform_device *pdev) +{ + int status; + struct spi_master *master; + struct spi_gpio *spi_gpio; + struct spi_gpio_platform_data *pdata; + u16 master_flags = 0; + bool use_of = 0; + int num_devices; + + status = spi_gpio_probe_dt(pdev); + if (status < 0) + return status; + if (status > 0) + use_of = 1; + + pdata = dev_get_platdata(&pdev->dev); +#ifdef GENERIC_BITBANG + if (!pdata || (!use_of && !pdata->num_chipselect)) + return -ENODEV; +#endif + + if (use_of && !SPI_N_CHIPSEL) + num_devices = 1; + else + num_devices = SPI_N_CHIPSEL; + + status = spi_gpio_request(pdata, dev_name(&pdev->dev), &master_flags); + if (status < 0) + return status; + + master = spi_alloc_master(&pdev->dev, sizeof(*spi_gpio) + + (sizeof(unsigned long) * num_devices)); + if (!master) { + status = -ENOMEM; + goto gpio_free; + } + spi_gpio = spi_master_get_devdata(master); + platform_set_drvdata(pdev, spi_gpio); + + spi_gpio->pdev = pdev; + if (pdata) + spi_gpio->pdata = *pdata; + + master->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 32); + master->flags = master_flags; + master->bus_num = pdev->id; + master->num_chipselect = num_devices; + master->setup = spi_gpio_setup; + master->cleanup = spi_gpio_cleanup; +#ifdef CONFIG_OF + master->dev.of_node = pdev->dev.of_node; + + if (use_of) { + int i; + struct device_node *np = pdev->dev.of_node; + + /* + * In DT environments, take the CS GPIO from the "cs-gpios" + * property of the node. + */ + + if (!SPI_N_CHIPSEL) + spi_gpio->cs_gpios[0] = SPI_GPIO_NO_CHIPSELECT; + else + for (i = 0; i < SPI_N_CHIPSEL; i++) { + status = of_get_named_gpio(np, "cs-gpios", i); + if (status < 0) { + dev_err(&pdev->dev, + "invalid cs-gpios property\n"); + goto gpio_free; + } + spi_gpio->cs_gpios[i] = status; + } + } +#endif + + spi_gpio->bitbang.master = master; + spi_gpio->bitbang.chipselect = spi_gpio_chipselect; + + if ((master_flags & (SPI_MASTER_NO_TX | SPI_MASTER_NO_RX)) == 0) { + spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_txrx_word_mode0; + spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_txrx_word_mode1; + spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_txrx_word_mode2; + spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_txrx_word_mode3; + } else { + spi_gpio->bitbang.txrx_word[SPI_MODE_0] = spi_gpio_spec_txrx_word_mode0; + spi_gpio->bitbang.txrx_word[SPI_MODE_1] = spi_gpio_spec_txrx_word_mode1; + spi_gpio->bitbang.txrx_word[SPI_MODE_2] = spi_gpio_spec_txrx_word_mode2; + spi_gpio->bitbang.txrx_word[SPI_MODE_3] = spi_gpio_spec_txrx_word_mode3; + } + spi_gpio->bitbang.setup_transfer = spi_bitbang_setup_transfer; + spi_gpio->bitbang.flags = SPI_CS_HIGH; + + status = spi_bitbang_start(&spi_gpio->bitbang); + if (status < 0) { +gpio_free: + if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO) + gpio_free(SPI_MISO_GPIO); + if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI) + gpio_free(SPI_MOSI_GPIO); + gpio_free(SPI_SCK_GPIO); + spi_master_put(master); + } + + return status; +} + +static int spi_gpio_remove(struct platform_device *pdev) +{ + struct spi_gpio *spi_gpio; + struct spi_gpio_platform_data *pdata; + + spi_gpio = platform_get_drvdata(pdev); + pdata = dev_get_platdata(&pdev->dev); + + /* stop() unregisters child devices too */ + spi_bitbang_stop(&spi_gpio->bitbang); + + if (SPI_MISO_GPIO != SPI_GPIO_NO_MISO) + gpio_free(SPI_MISO_GPIO); + if (SPI_MOSI_GPIO != SPI_GPIO_NO_MOSI) + gpio_free(SPI_MOSI_GPIO); + gpio_free(SPI_SCK_GPIO); + spi_master_put(spi_gpio->bitbang.master); + + return 0; +} + +MODULE_ALIAS("platform:" DRIVER_NAME); + +static struct platform_driver spi_gpio_driver = { + .driver = { + .name = DRIVER_NAME, + .of_match_table = of_match_ptr(spi_gpio_dt_ids), + }, + .probe = spi_gpio_probe, + .remove = spi_gpio_remove, +}; +module_platform_driver(spi_gpio_driver); + +MODULE_DESCRIPTION("SPI master driver using generic bitbanged GPIO "); +MODULE_AUTHOR("David Brownell"); +MODULE_LICENSE("GPL"); |