[linux.git] / drivers / spi / spi-bcm2835aux.c

/*
 * 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_IN_RISING	0x00000400
#define BCM2835_AUX_SPI_CNTL0_CLEARFIFO	0x00000200
#define BCM2835_AUX_SPI_CNTL0_OUT_RISING	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_TXEMPTY	0x00000080
#define BCM2835_AUX_SPI_CNTL1_IDLE	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

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 void bcm2835aux_spi_transfer_helper(struct bcm2835aux_spi *bs)
{
	/* 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);
	}

	/* 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);
	}
}

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);

	/* IRQ may be shared, so return if our interrupts are disabled */
	if (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_CNTL1) &
	      (BCM2835_AUX_SPI_CNTL1_TXEMPTY | BCM2835_AUX_SPI_CNTL1_IDLE)))
		return IRQ_NONE;

	/* do common fifo handling */
	bcm2835aux_spi_transfer_helper(bs);

	if (!bs->tx_len) {
		/* disable tx fifo empty interrupt */
		bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1] |
			BCM2835_AUX_SPI_CNTL1_IDLE);
	}

	/* and if rx_len is 0 then disable interrupts and wake up completion */
	if (!bs->rx_len) {
		bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
		complete(&master->xfer_completion);
	}

	return IRQ_HANDLED;
}

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;

	/* 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) {

		/* do common fifo handling */
		bcm2835aux_spi_transfer_helper(bs);

		/* 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);
		}
	}

	/* 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;

	/* 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
	 */

	/* 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;
	}
	/* mask out old speed from previous spi_transfer */
	bs->cntl[0] &= ~(BCM2835_AUX_SPI_CNTL0_SPEED);
	/* set the new speed */
	bs->cntl[0] |= speed << BCM2835_AUX_SPI_CNTL0_SPEED_SHIFT;

	spi_used_hz = clk_hz / (2 * (speed + 1));

	/* 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 cycles after each chunk getting
	 * transferred - in our case the chunk size is 3 bytes, so we
	 * approximate this by 9 cycles/byte.  This is used to find the number
	 * of Hz per byte per polling limit.  E.g., we can transfer 1 byte in
	 * 30 µs per 300,000 Hz of bus clock.
	 */
#define HZ_PER_BYTE ((9 * 1000000) / BCM2835_AUX_SPI_POLLING_LIMIT_US)
	/* run in polling mode for short transfers */
	if (tfr->len < spi_used_hz / HZ_PER_BYTE)
		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);
#undef HZ_PER_BYTE
}

static int bcm2835aux_spi_prepare_message(struct spi_master *master,
					  struct spi_message *msg)
{
	struct spi_device *spi = msg->spi;
	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);

	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;

	/* handle all the modes */
	if (spi->mode & SPI_CPOL) {
		bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_CPOL;
		bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_OUT_RISING;
	} else {
		bs->cntl[0] |= BCM2835_AUX_SPI_CNTL0_IN_RISING;
	}
	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]);

	return 0;
}

static int bcm2835aux_spi_unprepare_message(struct spi_master *master,
					    struct spi_message *msg)
{
	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);

	bcm2835aux_spi_reset_hw(bs);

	return 0;
}

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 = (SPI_CPOL | SPI_CS_HIGH | SPI_NO_CS);
	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->prepare_message = bcm2835aux_spi_prepare_message;
	master->unprepare_message = bcm2835aux_spi_unprepare_message;
	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 (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 <[email protected]>");
MODULE_LICENSE("GPL");
Commit	Line	Data
1ea29b39 MS	1	/*
	2	* Driver for Broadcom BCM2835 auxiliary SPI Controllers
	3	*
	4	* the driver does not rely on the native chipselects at all
	5	* but only uses the gpio type chipselects
	6	*
	7	* Based on: spi-bcm2835.c
	8	*
	9	* Copyright (C) 2015 Martin Sperl
	10	*
	11	* This program is free software; you can redistribute it and/or modify
	12	* it under the terms of the GNU General Public License as published by
	13	* the Free Software Foundation; either version 2 of the License, or
	14	* (at your option) any later version.
	15	*
	16	* This program is distributed in the hope that it will be useful,
	17	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	18	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	19	* GNU General Public License for more details.
	20	*/
	21
	22	#include <linux/clk.h>
	23	#include <linux/completion.h>
	24	#include <linux/delay.h>
	25	#include <linux/err.h>
	26	#include <linux/interrupt.h>
	27	#include <linux/io.h>
	28	#include <linux/kernel.h>
	29	#include <linux/module.h>
	30	#include <linux/of.h>
	31	#include <linux/of_address.h>
	32	#include <linux/of_device.h>
	33	#include <linux/of_gpio.h>
	34	#include <linux/of_irq.h>
	35	#include <linux/regmap.h>
	36	#include <linux/spi/spi.h>
	37	#include <linux/spinlock.h>
	38
	39	/*
	40	* spi register defines
	41	*
	42	* note there is garbage in the "official" documentation,
	43	* so some data is taken from the file:
	44	* brcm_usrlib/dag/vmcsx/vcinclude/bcm2708_chip/aux_io.h
	45	* inside of:
	46	* http://www.broadcom.com/docs/support/videocore/Brcm_Android_ICS_Graphics_Stack.tar.gz
	47	*/
	48
	49	/* SPI register offsets */
	50	#define BCM2835_AUX_SPI_CNTL0 0x00
	51	#define BCM2835_AUX_SPI_CNTL1 0x04
	52	#define BCM2835_AUX_SPI_STAT 0x08
	53	#define BCM2835_AUX_SPI_PEEK 0x0C
	54	#define BCM2835_AUX_SPI_IO 0x20
	55	#define BCM2835_AUX_SPI_TXHOLD 0x30
	56
	57	/* Bitfields in CNTL0 */
	58	#define BCM2835_AUX_SPI_CNTL0_SPEED 0xFFF00000
	59	#define BCM2835_AUX_SPI_CNTL0_SPEED_MAX 0xFFF
	60	#define BCM2835_AUX_SPI_CNTL0_SPEED_SHIFT 20
	61	#define BCM2835_AUX_SPI_CNTL0_CS 0x000E0000
	62	#define BCM2835_AUX_SPI_CNTL0_POSTINPUT 0x00010000
	63	#define BCM2835_AUX_SPI_CNTL0_VAR_CS 0x00008000
	64	#define BCM2835_AUX_SPI_CNTL0_VAR_WIDTH 0x00004000
65	#define BCM2835_AUX_SPI_CNTL0_DOUTHOLD 0x00003000
66	#define BCM2835_AUX_SPI_CNTL0_ENABLE 0x00000800
e9dd4edc	67	#define BCM2835_AUX_SPI_CNTL0_IN_RISING 0x00000400
1ea29b39	68	#define BCM2835_AUX_SPI_CNTL0_CLEARFIFO 0x00000200
e9dd4edc	69	#define BCM2835_AUX_SPI_CNTL0_OUT_RISING 0x00000100
1ea29b39 MS	70	#define BCM2835_AUX_SPI_CNTL0_CPOL 0x00000080
	71	#define BCM2835_AUX_SPI_CNTL0_MSBF_OUT 0x00000040
	72	#define BCM2835_AUX_SPI_CNTL0_SHIFTLEN 0x0000003F
	73
	74	/* Bitfields in CNTL1 */
	75	#define BCM2835_AUX_SPI_CNTL1_CSHIGH 0x00000700
fe0e2304 SO	76	#define BCM2835_AUX_SPI_CNTL1_TXEMPTY 0x00000080
fe0e2304 SO	77	#define BCM2835_AUX_SPI_CNTL1_IDLE 0x00000040
1ea29b39 MS	78	#define BCM2835_AUX_SPI_CNTL1_MSBF_IN 0x00000002
	79	#define BCM2835_AUX_SPI_CNTL1_KEEP_IN 0x00000001
	80
	81	/* Bitfields in STAT */
	82	#define BCM2835_AUX_SPI_STAT_TX_LVL 0xFF000000
	83	#define BCM2835_AUX_SPI_STAT_RX_LVL 0x00FF0000
	84	#define BCM2835_AUX_SPI_STAT_TX_FULL 0x00000400
	85	#define BCM2835_AUX_SPI_STAT_TX_EMPTY 0x00000200
	86	#define BCM2835_AUX_SPI_STAT_RX_FULL 0x00000100
	87	#define BCM2835_AUX_SPI_STAT_RX_EMPTY 0x00000080
	88	#define BCM2835_AUX_SPI_STAT_BUSY 0x00000040
	89	#define BCM2835_AUX_SPI_STAT_BITCOUNT 0x0000003F
	90
	91	/* timeout values */
	92	#define BCM2835_AUX_SPI_POLLING_LIMIT_US 30
	93	#define BCM2835_AUX_SPI_POLLING_JIFFIES 2
	94
1ea29b39 MS	95	struct bcm2835aux_spi {
	96	void __iomem *regs;
	97	struct clk *clk;
	98	int irq;
	99	u32 cntl[2];
	100	const u8 *tx_buf;
	101	u8 *rx_buf;
	102	int tx_len;
	103	int rx_len;
72aac02b	104	int pending;
1ea29b39 MS	105	};
	106
	107	static inline u32 bcm2835aux_rd(struct bcm2835aux_spi *bs, unsigned reg)
	108	{
	109	return readl(bs->regs + reg);
	110	}
	111
	112	static inline void bcm2835aux_wr(struct bcm2835aux_spi *bs, unsigned reg,
	113	u32 val)
	114	{
	115	writel(val, bs->regs + reg);
	116	}
	117
	118	static inline void bcm2835aux_rd_fifo(struct bcm2835aux_spi *bs)
	119	{
	120	u32 data;
1ea29b39 MS	121	int count = min(bs->rx_len, 3);
	122
	123	data = bcm2835aux_rd(bs, BCM2835_AUX_SPI_IO);
	124	if (bs->rx_buf) {
72aac02b MS	125	switch (count) {
	126	case 4:
	127	*bs->rx_buf++ = (data >> 24) & 0xff;
	128	/* fallthrough */
	129	case 3:
	130	*bs->rx_buf++ = (data >> 16) & 0xff;
	131	/* fallthrough */
	132	case 2:
	133	*bs->rx_buf++ = (data >> 8) & 0xff;
	134	/* fallthrough */
	135	case 1:
	136	*bs->rx_buf++ = (data >> 0) & 0xff;
	137	/* fallthrough - no default */
	138	}
1ea29b39 MS	139	}
1ea29b39 MS	140	bs->rx_len -= count;
72aac02b	141	bs->pending -= count;
1ea29b39 MS	142	}
	143
	144	static inline void bcm2835aux_wr_fifo(struct bcm2835aux_spi *bs)
	145	{
	146	u32 data;
	147	u8 byte;
	148	int count;
	149	int i;
	150
	151	/* gather up to 3 bytes to write to the FIFO */
	152	count = min(bs->tx_len, 3);
	153	data = 0;
	154	for (i = 0; i < count; i++) {
	155	byte = bs->tx_buf ? *bs->tx_buf++ : 0;
	156	data \|= byte << (8 * (2 - i));
	157	}
	158
	159	/* and set the variable bit-length */
	160	data \|= (count * 8) << 24;
	161
	162	/* and decrement length */
	163	bs->tx_len -= count;
72aac02b	164	bs->pending += count;
1ea29b39 MS	165
	166	/* write to the correct TX-register */
	167	if (bs->tx_len)
	168	bcm2835aux_wr(bs, BCM2835_AUX_SPI_TXHOLD, data);
	169	else
	170	bcm2835aux_wr(bs, BCM2835_AUX_SPI_IO, data);
	171	}
	172
	173	static void bcm2835aux_spi_reset_hw(struct bcm2835aux_spi *bs)
	174	{
	175	/* disable spi clearing fifo and interrupts */
	176	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, 0);
	177	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0,
	178	BCM2835_AUX_SPI_CNTL0_CLEARFIFO);
	179	}
	180
7188a6f0	181	static void bcm2835aux_spi_transfer_helper(struct bcm2835aux_spi *bs)
1ea29b39	182	{
1ea29b39 MS	183	/* check if we have data to read */
	184	while (bs->rx_len &&
	185	(!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) &
	186	BCM2835_AUX_SPI_STAT_RX_EMPTY))) {
	187	bcm2835aux_rd_fifo(bs);
1ea29b39 MS	188	}
	189
	190	/* check if we have data to write */
	191	while (bs->tx_len &&
72aac02b	192	(bs->pending < 12) &&
1ea29b39 MS	193	(!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) &
	194	BCM2835_AUX_SPI_STAT_TX_FULL))) {
	195	bcm2835aux_wr_fifo(bs);
1ea29b39	196	}
7188a6f0 MS	197	}
	198
	199	static irqreturn_t bcm2835aux_spi_interrupt(int irq, void *dev_id)
	200	{
	201	struct spi_master *master = dev_id;
	202	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
	203
	204	/* IRQ may be shared, so return if our interrupts are disabled */
	205	if (!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_CNTL1) &
	206	(BCM2835_AUX_SPI_CNTL1_TXEMPTY \| BCM2835_AUX_SPI_CNTL1_IDLE)))
	207	return IRQ_NONE;
	208
	209	/* do common fifo handling */
	210	bcm2835aux_spi_transfer_helper(bs);
1ea29b39	211
f29ab184 SO	212	if (!bs->tx_len) {
	213	/* disable tx fifo empty interrupt */
	214	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1] \|
	215	BCM2835_AUX_SPI_CNTL1_IDLE);
	216	}
	217
b4e2adef	218	/* and if rx_len is 0 then disable interrupts and wake up completion */
1ea29b39	219	if (!bs->rx_len) {
b4e2adef	220	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
1ea29b39 MS	221	complete(&master->xfer_completion);
	222	}
	223
7188a6f0	224	return IRQ_HANDLED;
1ea29b39 MS	225	}
	226
	227	static int __bcm2835aux_spi_transfer_one_irq(struct spi_master *master,
	228	struct spi_device *spi,
	229	struct spi_transfer *tfr)
	230	{
	231	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
	232
	233	/* enable interrupts */
	234	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1] \|
	235	BCM2835_AUX_SPI_CNTL1_TXEMPTY \|
	236	BCM2835_AUX_SPI_CNTL1_IDLE);
	237
	238	/* and wait for finish... */
	239	return 1;
	240	}
	241
	242	static int bcm2835aux_spi_transfer_one_irq(struct spi_master *master,
	243	struct spi_device *spi,
	244	struct spi_transfer *tfr)
	245	{
	246	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
	247
	248	/* fill in registers and fifos before enabling interrupts */
	249	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
	250	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]);
	251
	252	/* fill in tx fifo with data before enabling interrupts */
	253	while ((bs->tx_len) &&
72aac02b	254	(bs->pending < 12) &&
1ea29b39 MS	255	(!(bcm2835aux_rd(bs, BCM2835_AUX_SPI_STAT) &
	256	BCM2835_AUX_SPI_STAT_TX_FULL))) {
	257	bcm2835aux_wr_fifo(bs);
	258	}
	259
	260	/* now run the interrupt mode */
	261	return __bcm2835aux_spi_transfer_one_irq(master, spi, tfr);
	262	}
	263
	264	static int bcm2835aux_spi_transfer_one_poll(struct spi_master *master,
	265	struct spi_device *spi,
72aac02b	266	struct spi_transfer *tfr)
1ea29b39 MS	267	{
	268	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
	269	unsigned long timeout;
1ea29b39 MS	270
	271	/* configure spi */
	272	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
	273	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]);
	274
	275	/* set the timeout */
	276	timeout = jiffies + BCM2835_AUX_SPI_POLLING_JIFFIES;
	277
	278	/* loop until finished the transfer */
	279	while (bs->rx_len) {
1ea29b39	280
7188a6f0 MS	281	/* do common fifo handling */
7188a6f0 MS	282	bcm2835aux_spi_transfer_helper(bs);
1ea29b39 MS	283
	284	/* there is still data pending to read check the timeout */
	285	if (bs->rx_len && time_after(jiffies, timeout)) {
	286	dev_dbg_ratelimited(&spi->dev,
	287	"timeout period reached: jiffies: %lu remaining tx/rx: %d/%d - falling back to interrupt mode\n",
	288	jiffies - timeout,
	289	bs->tx_len, bs->rx_len);
	290	/* forward to interrupt handler */
	291	return __bcm2835aux_spi_transfer_one_irq(master,
	292	spi, tfr);
	293	}
	294	}
	295
1ea29b39 MS	296	/* and return without waiting for completion */
	297	return 0;
	298	}
	299
	300	static int bcm2835aux_spi_transfer_one(struct spi_master *master,
	301	struct spi_device *spi,
	302	struct spi_transfer *tfr)
	303	{
	304	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
	305	unsigned long spi_hz, clk_hz, speed;
72aac02b	306	unsigned long spi_used_hz;
1ea29b39 MS	307
	308	/* calculate the registers to handle
	309	*
	310	* note that we use the variable data mode, which
	311	* is not optimal for longer transfers as we waste registers
	312	* resulting (potentially) in more interrupts when transferring
	313	* more than 12 bytes
	314	*/
1ea29b39 MS	315
	316	/* set clock */
	317	spi_hz = tfr->speed_hz;
	318	clk_hz = clk_get_rate(bs->clk);
	319
	320	if (spi_hz >= clk_hz / 2) {
	321	speed = 0;
	322	} else if (spi_hz) {
	323	speed = DIV_ROUND_UP(clk_hz, 2 * spi_hz) - 1;
	324	if (speed > BCM2835_AUX_SPI_CNTL0_SPEED_MAX)
	325	speed = BCM2835_AUX_SPI_CNTL0_SPEED_MAX;
	326	} else { /* the slowest we can go */
	327	speed = BCM2835_AUX_SPI_CNTL0_SPEED_MAX;
	328	}
b4e2adef SO	329	/* mask out old speed from previous spi_transfer */
	330	bs->cntl[0] &= ~(BCM2835_AUX_SPI_CNTL0_SPEED);
	331	/* set the new speed */
1ea29b39 MS	332	bs->cntl[0] \|= speed << BCM2835_AUX_SPI_CNTL0_SPEED_SHIFT;
	333
	334	spi_used_hz = clk_hz / (2 * (speed + 1));
	335
1ea29b39 MS	336	/* set transmit buffers and length */
	337	bs->tx_buf = tfr->tx_buf;
	338	bs->rx_buf = tfr->rx_buf;
	339	bs->tx_len = tfr->len;
	340	bs->rx_len = tfr->len;
72aac02b	341	bs->pending = 0;
1ea29b39	342
d704afff TP	343	/* Calculate the estimated time in us the transfer runs. Note that
	344	* there are are 2 idle clocks cycles after each chunk getting
	345	* transferred - in our case the chunk size is 3 bytes, so we
	346	* approximate this by 9 cycles/byte. This is used to find the number
	347	* of Hz per byte per polling limit. E.g., we can transfer 1 byte in
	348	* 30 µs per 300,000 Hz of bus clock.
72aac02b	349	*/
d704afff	350	#define HZ_PER_BYTE ((9 * 1000000) / BCM2835_AUX_SPI_POLLING_LIMIT_US)
1ea29b39	351	/* run in polling mode for short transfers */
d704afff	352	if (tfr->len < spi_used_hz / HZ_PER_BYTE)
72aac02b	353	return bcm2835aux_spi_transfer_one_poll(master, spi, tfr);
1ea29b39 MS	354
	355	/* run in interrupt mode for all others */
	356	return bcm2835aux_spi_transfer_one_irq(master, spi, tfr);
d704afff	357	#undef HZ_PER_BYTE
1ea29b39 MS	358	}
1ea29b39 MS	359
b4e2adef SO	360	static int bcm2835aux_spi_prepare_message(struct spi_master *master,
	361	struct spi_message *msg)
	362	{
	363	struct spi_device *spi = msg->spi;
	364	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
	365
	366	bs->cntl[0] = BCM2835_AUX_SPI_CNTL0_ENABLE \|
	367	BCM2835_AUX_SPI_CNTL0_VAR_WIDTH \|
	368	BCM2835_AUX_SPI_CNTL0_MSBF_OUT;
	369	bs->cntl[1] = BCM2835_AUX_SPI_CNTL1_MSBF_IN;
	370
	371	/* handle all the modes */
e9dd4edc	372	if (spi->mode & SPI_CPOL) {
b4e2adef	373	bs->cntl[0] \|= BCM2835_AUX_SPI_CNTL0_CPOL;
e9dd4edc SO	374	bs->cntl[0] \|= BCM2835_AUX_SPI_CNTL0_OUT_RISING;
	375	} else {
	376	bs->cntl[0] \|= BCM2835_AUX_SPI_CNTL0_IN_RISING;
	377	}
b4e2adef SO	378	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL1, bs->cntl[1]);
	379	bcm2835aux_wr(bs, BCM2835_AUX_SPI_CNTL0, bs->cntl[0]);
	380
	381	return 0;
	382	}
	383
	384	static int bcm2835aux_spi_unprepare_message(struct spi_master *master,
	385	struct spi_message *msg)
	386	{
	387	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
	388
	389	bcm2835aux_spi_reset_hw(bs);
	390
	391	return 0;
	392	}
	393
1ea29b39 MS	394	static void bcm2835aux_spi_handle_err(struct spi_master *master,
	395	struct spi_message *msg)
	396	{
	397	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
	398
	399	bcm2835aux_spi_reset_hw(bs);
	400	}
	401
	402	static int bcm2835aux_spi_probe(struct platform_device *pdev)
	403	{
	404	struct spi_master *master;
	405	struct bcm2835aux_spi *bs;
	406	struct resource *res;
	407	unsigned long clk_hz;
	408	int err;
	409
	410	master = spi_alloc_master(&pdev->dev, sizeof(*bs));
	411	if (!master) {
	412	dev_err(&pdev->dev, "spi_alloc_master() failed\n");
	413	return -ENOMEM;
	414	}
	415
	416	platform_set_drvdata(pdev, master);
e9dd4edc	417	master->mode_bits = (SPI_CPOL \| SPI_CS_HIGH \| SPI_NO_CS);
1ea29b39 MS	418	master->bits_per_word_mask = SPI_BPW_MASK(8);
	419	master->num_chipselect = -1;
	420	master->transfer_one = bcm2835aux_spi_transfer_one;
	421	master->handle_err = bcm2835aux_spi_handle_err;
b4e2adef SO	422	master->prepare_message = bcm2835aux_spi_prepare_message;
b4e2adef SO	423	master->unprepare_message = bcm2835aux_spi_unprepare_message;
1ea29b39 MS	424	master->dev.of_node = pdev->dev.of_node;
	425
	426	bs = spi_master_get_devdata(master);
	427
	428	/* the main area */
	429	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	430	bs->regs = devm_ioremap_resource(&pdev->dev, res);
	431	if (IS_ERR(bs->regs)) {
	432	err = PTR_ERR(bs->regs);
	433	goto out_master_put;
	434	}
	435
	436	bs->clk = devm_clk_get(&pdev->dev, NULL);
bfc7af6d	437	if (IS_ERR(bs->clk)) {
1ea29b39 MS	438	err = PTR_ERR(bs->clk);
	439	dev_err(&pdev->dev, "could not get clk: %d\n", err);
	440	goto out_master_put;
	441	}
	442
07bce09e	443	bs->irq = platform_get_irq(pdev, 0);
1ea29b39 MS	444	if (bs->irq <= 0) {
	445	dev_err(&pdev->dev, "could not get IRQ: %d\n", bs->irq);
	446	err = bs->irq ? bs->irq : -ENODEV;
	447	goto out_master_put;
	448	}
	449
	450	/* this also enables the HW block */
	451	err = clk_prepare_enable(bs->clk);
	452	if (err) {
	453	dev_err(&pdev->dev, "could not prepare clock: %d\n", err);
	454	goto out_master_put;
	455	}
	456
	457	/* just checking if the clock returns a sane value */
	458	clk_hz = clk_get_rate(bs->clk);
	459	if (!clk_hz) {
	460	dev_err(&pdev->dev, "clock returns 0 Hz\n");
	461	err = -ENODEV;
	462	goto out_clk_disable;
	463	}
	464
07bce09e MS	465	/* reset SPI-HW block */
	466	bcm2835aux_spi_reset_hw(bs);
	467
1ea29b39 MS	468	err = devm_request_irq(&pdev->dev, bs->irq,
	469	bcm2835aux_spi_interrupt,
	470	IRQF_SHARED,
	471	dev_name(&pdev->dev), master);
	472	if (err) {
	473	dev_err(&pdev->dev, "could not request IRQ: %d\n", err);
	474	goto out_clk_disable;
	475	}
	476
1ea29b39 MS	477	err = devm_spi_register_master(&pdev->dev, master);
	478	if (err) {
	479	dev_err(&pdev->dev, "could not register SPI master: %d\n", err);
	480	goto out_clk_disable;
	481	}
	482
	483	return 0;
	484
	485	out_clk_disable:
	486	clk_disable_unprepare(bs->clk);
	487	out_master_put:
	488	spi_master_put(master);
	489	return err;
	490	}
	491
	492	static int bcm2835aux_spi_remove(struct platform_device *pdev)
	493	{
	494	struct spi_master *master = platform_get_drvdata(pdev);
	495	struct bcm2835aux_spi *bs = spi_master_get_devdata(master);
	496
	497	bcm2835aux_spi_reset_hw(bs);
	498
	499	/* disable the HW block by releasing the clock */
	500	clk_disable_unprepare(bs->clk);
	501
	502	return 0;
	503	}
	504
	505	static const struct of_device_id bcm2835aux_spi_match[] = {
	506	{ .compatible = "brcm,bcm2835-aux-spi", },
	507	{}
	508	};
	509	MODULE_DEVICE_TABLE(of, bcm2835aux_spi_match);
	510
	511	static struct platform_driver bcm2835aux_spi_driver = {
	512	.driver = {
	513	.name = "spi-bcm2835aux",
	514	.of_match_table = bcm2835aux_spi_match,
	515	},
	516	.probe = bcm2835aux_spi_probe,
	517	.remove = bcm2835aux_spi_remove,
	518	};
	519	module_platform_driver(bcm2835aux_spi_driver);
	520
	521	MODULE_DESCRIPTION("SPI controller driver for Broadcom BCM2835 aux");
	522	MODULE_AUTHOR("Martin Sperl <[email protected]>");
22bf6cd2	523	MODULE_LICENSE("GPL");