diff options
Diffstat (limited to 'drivers/spi/spi-bcm2835aux.c')
| -rw-r--r-- | drivers/spi/spi-bcm2835aux.c | 512 |
1 files changed, 512 insertions, 0 deletions
diff --git a/drivers/spi/spi-bcm2835aux.c b/drivers/spi/spi-bcm2835aux.c new file mode 100644 index 000000000..7de6f8472 --- /dev/null +++ b/drivers/spi/spi-bcm2835aux.c @@ -0,0 +1,512 @@ +/* + * Driver for Broadcom BCM2835 auxiliary SPI Controllers + * + * the driver does not rely on the native chipselects at all + * but only uses the gpio type chipselects + * + * Based on: spi-bcm2835.c + * + * Copyright (C) 2015 Martin Sperl + * + * 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/clk.h> +#include <linux/completion.h> +#include <linux/delay.h> +#include <linux/err.h> +#include <linux/interrupt.h> +#include <linux/io.h> +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/of.h> +#include <linux/of_address.h> +#include <linux/of_device.h> +#include <linux/of_gpio.h> +#include <linux/of_irq.h> +#include <linux/regmap.h> +#include <linux/spi/spi.h> +#include <linux/spinlock.h> + +/* + * spi register defines + * + * note there is garbage in the "official" documentation, + * so some data is taken from the file: + * brcm_usrlib/dag/vmcsx/vcinclude/bcm2708_chip/aux_io.h + * inside of: + * http://www.broadcom.com/docs/support/videocore/Brcm_Android_ICS_Graphics_Stack.tar.gz + */ + +/* SPI register offsets */ +#define BCM2835_AUX_SPI_CNTL0 0x00 +#define BCM2835_AUX_SPI_CNTL1 0x04 +#define BCM2835_AUX_SPI_STAT 0x08 +#define BCM2835_AUX_SPI_PEEK 0x0C +#define BCM2835_AUX_SPI_IO 0x20 +#define BCM2835_AUX_SPI_TXHOLD 0x30 + +/* Bitfields in CNTL0 */ +#define BCM2835_AUX_SPI_CNTL0_SPEED 0xFFF00000 +#define BCM2835_AUX_SPI_CNTL0_SPEED_MAX 0xFFF +#define BCM2835_AUX_SPI_CNTL0_SPEED_SHIFT 20 +#define BCM2835_AUX_SPI_CNTL0_CS 0x000E0000 +#define BCM2835_AUX_SPI_CNTL0_POSTINPUT 0x00010000 +#define BCM2835_AUX_SPI_CNTL0_VAR_CS 0x00008000 +#define BCM2835_AUX_SPI_CNTL0_VAR_WIDTH 0x00004000 +#define BCM2835_AUX_SPI_CNTL0_DOUTHOLD 0x00003000 +#define BCM2835_AUX_SPI_CNTL0_ENABLE 0x00000800 +#define BCM2835_AUX_SPI_CNTL0_CPHA_IN 0x00000400 +#define BCM2835_AUX_SPI_CNTL0_CLEARFIFO 0x00000200 +#define BCM2835_AUX_SPI_CNTL0_CPHA_OUT 0x00000100 +#define BCM2835_AUX_SPI_CNTL0_CPOL 0x00000080 +#define BCM2835_AUX_SPI_CNTL0_MSBF_OUT 0x00000040 +#define BCM2835_AUX_SPI_CNTL0_SHIFTLEN 0x0000003F + +/* Bitfields in CNTL1 */ +#define BCM2835_AUX_SPI_CNTL1_CSHIGH 0x00000700 +#define BCM2835_AUX_SPI_CNTL1_IDLE 0x00000080 +#define BCM2835_AUX_SPI_CNTL1_TXEMPTY 0x00000040 +#define BCM2835_AUX_SPI_CNTL1_MSBF_IN 0x00000002 +#define BCM2835_AUX_SPI_CNTL1_KEEP_IN 0x00000001 + +/* Bitfields in STAT */ +#define BCM2835_AUX_SPI_STAT_TX_LVL 0xFF000000 +#define BCM2835_AUX_SPI_STAT_RX_LVL 0x00FF0000 +#define BCM2835_AUX_SPI_STAT_TX_FULL 0x00000400 +#define BCM2835_AUX_SPI_STAT_TX_EMPTY 0x00000200 +#define BCM2835_AUX_SPI_STAT_RX_FULL 0x00000100 +#define BCM2835_AUX_SPI_STAT_RX_EMPTY 0x00000080 +#define BCM2835_AUX_SPI_STAT_BUSY 0x00000040 +#define BCM2835_AUX_SPI_STAT_BITCOUNT 0x0000003F + +/* timeout values */ +#define BCM2835_AUX_SPI_POLLING_LIMIT_US 30 +#define BCM2835_AUX_SPI_POLLING_JIFFIES 2 + +#define BCM2835_AUX_SPI_MODE_BITS (SPI_CPOL | SPI_CPHA | SPI_CS_HIGH \ + | SPI_NO_CS) + +struct bcm2835aux_spi { + void __iomem *regs; + struct clk *clk; + int irq; + u32 cntl[2]; + const u8 *tx_buf; + u8 *rx_buf; + int tx_len; + int rx_len; + int pending; +}; + +static inline u32 bcm2835aux_rd(struct bcm2835aux_spi *bs, unsigned reg) +{ + return readl(bs->regs + reg); +} + +static inline void bcm2835aux_wr(struct bcm2835aux_spi *bs, unsigned reg, + u32 val) +{ + writel(val, bs->regs + reg); +} + +static inline void bcm2835aux_rd_fifo(struct bcm2835aux_spi *bs) +{ + u32 data; + int count = min(bs->rx_len, 3); + + data = bcm2835aux_rd(bs, BCM2835_AUX_SPI_IO); + if (bs->rx_buf) { + switch (count) { + case 4: + *bs->rx_buf++ = (data >> 24) & 0xff; + /* fallthrough */ + case 3: + *bs->rx_buf++ = (data >> 16) & 0xff; + /* fallthrough */ + case 2: + *bs->rx_buf++ = (data >> 8) & 0xff; + /* fallthrough */ + case 1: + *bs->rx_buf++ = (data >> 0) & 0xff; + /* fallthrough - no default */ + } + } + bs->rx_len -= count; + bs->pending -= count; +} + +static inline void bcm2835aux_wr_fifo(struct bcm2835aux_spi *bs) +{ + u32 data; + u8 byte; + int count; + int i; + + /* gather up to 3 bytes to write to the FIFO */ + count = min(bs->tx_len, 3); + data = 0; + for (i = 0; i < count; i++) { + byte = bs->tx_buf ? *bs->tx_buf++ : 0; + data |= byte << (8 * (2 - i)); + } + + /* and set the variable bit-length */ + data |= (count * 8) << 24; + + /* and decrement length */ + bs->tx_len -= count; + bs->pending += count; + + /* write to the correct TX-register */ + if (bs->tx_len) + bcm2835aux_wr(bs, BCM2835_AUX_SPI_TXHOLD, data); + else + bcm2835aux_wr(bs, BCM2835_AUX_SPI_IO, data); +} + +static void bcm2835aux_spi_reset_hw(struct bcm2835aux_spi *bs) +{ + /* disable spi clearing fifo and interrupts */ + bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, 0); + bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, + BCM2835_AUX_SPI_CNTL0_CLEARFIFO); +} + +static irqreturn_t bcm2835aux_spi_interrupt(int irq, void *dev_id) +{ + struct spi_master *master = dev_id; + struct bcm2835aux_spi *bs = spi_master_get_devdata(master); + irqreturn_t ret = IRQ_NONE; + + /* check if we have data to read */ + while (bs->rx_len && + (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) & + BCM2835_AUX_SPI_STAT_RX_EMPTY))) { + bcm2835aux_rd_fifo(bs); + ret = IRQ_HANDLED; + } + + /* check if we have data to write */ + while (bs->tx_len && + (bs->pending < 12) && + (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) & + BCM2835_AUX_SPI_STAT_TX_FULL))) { + bcm2835aux_wr_fifo(bs); + ret = IRQ_HANDLED; + } + + /* and check if we have reached "done" */ + while (bs->rx_len && + (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) & + BCM2835_AUX_SPI_STAT_BUSY))) { + bcm2835aux_rd_fifo(bs); + ret = IRQ_HANDLED; + } + + /* and if rx_len is 0 then wake up completion and disable spi */ + if (!bs->rx_len) { + bcm2835aux_spi_reset_hw(bs); + complete(&master->xfer_completion); + } + + /* and return */ + return ret; +} + +static int __bcm2835aux_spi_transfer_one_irq(struct spi_master *master, + struct spi_device *spi, + struct spi_transfer *tfr) +{ + struct bcm2835aux_spi *bs = spi_master_get_devdata(master); + + /* enable interrupts */ + bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1] | + BCM2835_AUX_SPI_CNTL1_TXEMPTY | + BCM2835_AUX_SPI_CNTL1_IDLE); + + /* and wait for finish... */ + return 1; +} + +static int bcm2835aux_spi_transfer_one_irq(struct spi_master *master, + struct spi_device *spi, + struct spi_transfer *tfr) +{ + struct bcm2835aux_spi *bs = spi_master_get_devdata(master); + + /* fill in registers and fifos before enabling interrupts */ + bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]); + bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]); + + /* fill in tx fifo with data before enabling interrupts */ + while ((bs->tx_len) && + (bs->pending < 12) && + (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) & + BCM2835_AUX_SPI_STAT_TX_FULL))) { + bcm2835aux_wr_fifo(bs); + } + + /* now run the interrupt mode */ + return __bcm2835aux_spi_transfer_one_irq(master, spi, tfr); +} + +static int bcm2835aux_spi_transfer_one_poll(struct spi_master *master, + struct spi_device *spi, + struct spi_transfer *tfr) +{ + struct bcm2835aux_spi *bs = spi_master_get_devdata(master); + unsigned long timeout; + u32 stat; + + /* configure spi */ + bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]); + bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]); + + /* set the timeout */ + timeout = jiffies + BCM2835_AUX_SPI_POLLING_JIFFIES; + + /* loop until finished the transfer */ + while (bs->rx_len) { + /* read status */ + stat = bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT); + + /* fill in tx fifo with remaining data */ + if ((bs->tx_len) && (!(stat & BCM2835_AUX_SPI_STAT_TX_FULL))) { + bcm2835aux_wr_fifo(bs); + continue; + } + + /* read data from fifo for both cases */ + if (!(stat & BCM2835_AUX_SPI_STAT_RX_EMPTY)) { + bcm2835aux_rd_fifo(bs); + continue; + } + if (!(stat & BCM2835_AUX_SPI_STAT_BUSY)) { + bcm2835aux_rd_fifo(bs); + continue; + } + + /* there is still data pending to read check the timeout */ + if (bs->rx_len && time_after(jiffies, timeout)) { + dev_dbg_ratelimited(&spi->dev, + "timeout period reached: jiffies: %lu remaining tx/rx: %d/%d - falling back to interrupt mode\n", + jiffies - timeout, + bs->tx_len, bs->rx_len); + /* forward to interrupt handler */ + return __bcm2835aux_spi_transfer_one_irq(master, + spi, tfr); + } + } + + /* Transfer complete - reset SPI HW */ + bcm2835aux_spi_reset_hw(bs); + + /* and return without waiting for completion */ + return 0; +} + +static int bcm2835aux_spi_transfer_one(struct spi_master *master, + struct spi_device *spi, + struct spi_transfer *tfr) +{ + struct bcm2835aux_spi *bs = spi_master_get_devdata(master); + unsigned long spi_hz, clk_hz, speed; + unsigned long spi_used_hz; + unsigned long long xfer_time_us; + + /* calculate the registers to handle + * + * note that we use the variable data mode, which + * is not optimal for longer transfers as we waste registers + * resulting (potentially) in more interrupts when transferring + * more than 12 bytes + */ + bs->cntl[0] = BCM2835_AUX_SPI_CNTL0_ENABLE | + BCM2835_AUX_SPI_CNTL0_VAR_WIDTH | + BCM2835_AUX_SPI_CNTL0_MSBF_OUT; + bs->cntl[1] = BCM2835_AUX_SPI_CNTL1_MSBF_IN; + + /* set clock */ + spi_hz = tfr->speed_hz; + clk_hz = clk_get_rate(bs->clk); + + if (spi_hz >= clk_hz / 2) { + speed = 0; + } else if (spi_hz) { + speed = DIV_ROUND_UP(clk_hz, 2 * spi_hz) - 1; + if (speed > BCM2835_AUX_SPI_CNTL0_SPEED_MAX) + speed = BCM2835_AUX_SPI_CNTL0_SPEED_MAX; + } else { /* the slowest we can go */ + speed = BCM2835_AUX_SPI_CNTL0_SPEED_MAX; + } + bs->cntl[0] |= speed << BCM2835_AUX_SPI_CNTL0_SPEED_SHIFT; + + spi_used_hz = clk_hz / (2 * (speed + 1)); + + /* handle all the modes */ + if (spi->mode & SPI_CPOL) + bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_CPOL; + if (spi->mode & SPI_CPHA) + bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_CPHA_OUT | + BCM2835_AUX_SPI_CNTL0_CPHA_IN; + + /* set transmit buffers and length */ + bs->tx_buf = tfr->tx_buf; + bs->rx_buf = tfr->rx_buf; + bs->tx_len = tfr->len; + bs->rx_len = tfr->len; + bs->pending = 0; + + /* calculate the estimated time in us the transfer runs + * note that there are are 2 idle clocks after each + * chunk getting transferred - in our case the chunk size + * is 3 bytes, so we approximate this by 9 bits/byte + */ + xfer_time_us = tfr->len * 9 * 1000000; + do_div(xfer_time_us, spi_used_hz); + + /* run in polling mode for short transfers */ + if (xfer_time_us < BCM2835_AUX_SPI_POLLING_LIMIT_US) + return bcm2835aux_spi_transfer_one_poll(master, spi, tfr); + + /* run in interrupt mode for all others */ + return bcm2835aux_spi_transfer_one_irq(master, spi, tfr); +} + +static void bcm2835aux_spi_handle_err(struct spi_master *master, + struct spi_message *msg) +{ + struct bcm2835aux_spi *bs = spi_master_get_devdata(master); + + bcm2835aux_spi_reset_hw(bs); +} + +static int bcm2835aux_spi_probe(struct platform_device *pdev) +{ + struct spi_master *master; + struct bcm2835aux_spi *bs; + struct resource *res; + unsigned long clk_hz; + int err; + + master = spi_alloc_master(&pdev->dev, sizeof(*bs)); + if (!master) { + dev_err(&pdev->dev, "spi_alloc_master() failed\n"); + return -ENOMEM; + } + + platform_set_drvdata(pdev, master); + master->mode_bits = BCM2835_AUX_SPI_MODE_BITS; + master->bits_per_word_mask = SPI_BPW_MASK(8); + master->num_chipselect = -1; + master->transfer_one = bcm2835aux_spi_transfer_one; + master->handle_err = bcm2835aux_spi_handle_err; + master->dev.of_node = pdev->dev.of_node; + + bs = spi_master_get_devdata(master); + + /* the main area */ + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); + bs->regs = devm_ioremap_resource(&pdev->dev, res); + if (IS_ERR(bs->regs)) { + err = PTR_ERR(bs->regs); + goto out_master_put; + } + + bs->clk = devm_clk_get(&pdev->dev, NULL); + if ((!bs->clk) || (IS_ERR(bs->clk))) { + err = PTR_ERR(bs->clk); + dev_err(&pdev->dev, "could not get clk: %d\n", err); + goto out_master_put; + } + + bs->irq = platform_get_irq(pdev, 0); + if (bs->irq <= 0) { + dev_err(&pdev->dev, "could not get IRQ: %d\n", bs->irq); + err = bs->irq ? bs->irq : -ENODEV; + goto out_master_put; + } + + /* this also enables the HW block */ + err = clk_prepare_enable(bs->clk); + if (err) { + dev_err(&pdev->dev, "could not prepare clock: %d\n", err); + goto out_master_put; + } + + /* just checking if the clock returns a sane value */ + clk_hz = clk_get_rate(bs->clk); + if (!clk_hz) { + dev_err(&pdev->dev, "clock returns 0 Hz\n"); + err = -ENODEV; + goto out_clk_disable; + } + + /* reset SPI-HW block */ + bcm2835aux_spi_reset_hw(bs); + + err = devm_request_irq(&pdev->dev, bs->irq, + bcm2835aux_spi_interrupt, + IRQF_SHARED, + dev_name(&pdev->dev), master); + if (err) { + dev_err(&pdev->dev, "could not request IRQ: %d\n", err); + goto out_clk_disable; + } + + err = devm_spi_register_master(&pdev->dev, master); + if (err) { + dev_err(&pdev->dev, "could not register SPI master: %d\n", err); + goto out_clk_disable; + } + + return 0; + +out_clk_disable: + clk_disable_unprepare(bs->clk); +out_master_put: + spi_master_put(master); + return err; +} + +static int bcm2835aux_spi_remove(struct platform_device *pdev) +{ + struct spi_master *master = platform_get_drvdata(pdev); + struct bcm2835aux_spi *bs = spi_master_get_devdata(master); + + bcm2835aux_spi_reset_hw(bs); + + /* disable the HW block by releasing the clock */ + clk_disable_unprepare(bs->clk); + + return 0; +} + +static const struct of_device_id bcm2835aux_spi_match[] = { + { .compatible = "brcm,bcm2835-aux-spi", }, + {} +}; +MODULE_DEVICE_TABLE(of, bcm2835aux_spi_match); + +static struct platform_driver bcm2835aux_spi_driver = { + .driver = { + .name = "spi-bcm2835aux", + .of_match_table = bcm2835aux_spi_match, + }, + .probe = bcm2835aux_spi_probe, + .remove = bcm2835aux_spi_remove, +}; +module_platform_driver(bcm2835aux_spi_driver); + +MODULE_DESCRIPTION("SPI controller driver for Broadcom BCM2835 aux"); +MODULE_AUTHOR("Martin Sperl <kernel@martin.sperl.org>"); +MODULE_LICENSE("GPL v2"); |