mcp23s08.c

/*
 * mcp23s08.c - SPI gpio expander driver
 */

#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/workqueue.h>
#include <linux/mutex.h>

#include <linux/spi/spi.h>
#include <linux/spi/mcp23s08.h>

#include <asm/gpio.h>


/* Registers are all 8 bits wide.
 *
 * The mcp23s17 has twice as many bits, and can be configured to work
 * with either 16 bit registers or with two adjacent 8 bit banks.
 *
 * Also, there are I2C versions of both chips.
 */
#define MCP_IODIR	0x00		/* init/reset:  all ones */
#define MCP_IPOL	0x01
#define MCP_GPINTEN	0x02
#define MCP_DEFVAL	0x03
#define MCP_INTCON	0x04
#define MCP_IOCON	0x05
#	define IOCON_SEQOP	(1 << 5)
#	define IOCON_HAEN	(1 << 3)
#	define IOCON_ODR	(1 << 2)
#	define IOCON_INTPOL	(1 << 1)
#define MCP_GPPU	0x06
#define MCP_INTF	0x07
#define MCP_INTCAP	0x08
#define MCP_GPIO	0x09
#define MCP_OLAT	0x0a

struct mcp23s08 {
	struct spi_device	*spi;
	u8			addr;

	/* lock protects the cached values */
	struct mutex		lock;
	u8			cache[11];

	struct gpio_chip	chip;

	struct work_struct	work;
};

static int mcp23s08_read(struct mcp23s08 *mcp, unsigned reg)
{
	u8	tx[2], rx[1];
	int	status;

	tx[0] = mcp->addr | 0x01;
	tx[1] = reg;
	status = spi_write_then_read(mcp->spi, tx, sizeof tx, rx, sizeof rx);
	return (status < 0) ? status : rx[0];
}

static int mcp23s08_write(struct mcp23s08 *mcp, unsigned reg, u8 val)
{
	u8	tx[3];

	tx[0] = mcp->addr;
	tx[1] = reg;
	tx[2] = val;
	return spi_write_then_read(mcp->spi, tx, sizeof tx, NULL, 0);
}

static int
mcp23s08_read_regs(struct mcp23s08 *mcp, unsigned reg, u8 *vals, unsigned n)
{
	u8	tx[2];

	if ((n + reg) > sizeof mcp->cache)
		return -EINVAL;
	tx[0] = mcp->addr | 0x01;
	tx[1] = reg;
	return spi_write_then_read(mcp->spi, tx, sizeof tx, vals, n);
}

/*----------------------------------------------------------------------*/

static int mcp23s08_direction_input(struct gpio_chip *chip, unsigned offset)
{
	struct mcp23s08	*mcp = container_of(chip, struct mcp23s08, chip);
	int status;

	mutex_lock(&mcp->lock);
	mcp->cache[MCP_IODIR] |= (1 << offset);
	status = mcp23s08_write(mcp, MCP_IODIR, mcp->cache[MCP_IODIR]);
	mutex_unlock(&mcp->lock);
	return status;
}

static int mcp23s08_get(struct gpio_chip *chip, unsigned offset)
{
	struct mcp23s08	*mcp = container_of(chip, struct mcp23s08, chip);
	int status;

	mutex_lock(&mcp->lock);

	/* REVISIT reading this clears any IRQ ... */
	status = mcp23s08_read(mcp, MCP_GPIO);
	if (status < 0)
		status = 0;
	else {
		mcp->cache[MCP_GPIO] = status;
		status = !!(status & (1 << offset));
	}
	mutex_unlock(&mcp->lock);
	return status;
}

static int __mcp23s08_set(struct mcp23s08 *mcp, unsigned mask, int value)
{
	u8 olat = mcp->cache[MCP_OLAT];

	if (value)
		olat |= mask;
	else
		olat &= ~mask;
	mcp->cache[MCP_OLAT] = olat;
	return mcp23s08_write(mcp, MCP_OLAT, olat);
}

static void mcp23s08_set(struct gpio_chip *chip, unsigned offset, int value)
{
	struct mcp23s08	*mcp = container_of(chip, struct mcp23s08, chip);
	u8 mask = 1 << offset;

	mutex_lock(&mcp->lock);
	__mcp23s08_set(mcp, mask, value);
	mutex_unlock(&mcp->lock);
}

static int
mcp23s08_direction_output(struct gpio_chip *chip, unsigned offset, int value)
{
	struct mcp23s08	*mcp = container_of(chip, struct mcp23s08, chip);
	u8 mask = 1 << offset;
	int status;

	mutex_lock(&mcp->lock);
	status = __mcp23s08_set(mcp, mask, value);
	if (status == 0) {
		mcp->cache[MCP_IODIR] &= ~mask;
		status = mcp23s08_write(mcp, MCP_IODIR, mcp->cache[MCP_IODIR]);
	}
	mutex_unlock(&mcp->lock);
	return status;
}

/*----------------------------------------------------------------------*/

#ifdef CONFIG_DEBUG_FS

#include <linux/seq_file.h>

/*
 * This shows more info than the generic gpio dump code:
 * pullups, deglitching, open drain drive.
 */
static void mcp23s08_dbg_show(struct seq_file *s, struct gpio_chip *chip)
{
	struct mcp23s08	*mcp;
	char		bank;
	int		t;
	unsigned	mask;

	mcp = container_of(chip, struct mcp23s08, chip);

	/* NOTE: we only handle one bank for now ... */
	bank = '0' + ((mcp->addr >> 1) & 0x3);

	mutex_lock(&mcp->lock);
	t = mcp23s08_read_regs(mcp, 0, mcp->cache, sizeof mcp->cache);
	if (t < 0) {
		seq_printf(s, " I/O ERROR %d\n", t);
		goto done;
	}

	for (t = 0, mask = 1; t < 8; t++, mask <<= 1) {
		const char	*label;

		label = gpiochip_is_requested(chip, t);
		if (!label)
			continue;

		seq_printf(s, " gpio-%-3d P%c.%d (%-12s) %s %s %s",
			chip->base + t, bank, t, label,
			(mcp->cache[MCP_IODIR] & mask) ? "in " : "out",
			(mcp->cache[MCP_GPIO] & mask) ? "hi" : "lo",
			(mcp->cache[MCP_GPPU] & mask) ? "  " : "up");
		/* NOTE:  ignoring the irq-related registers */
		seq_printf(s, "\n");
	}
done:
	mutex_unlock(&mcp->lock);
}

#else
#define mcp23s08_dbg_show	NULL
#endif

/*----------------------------------------------------------------------*/

static int mcp23s08_probe(struct spi_device *spi)
{
	struct mcp23s08			*mcp;
	struct mcp23s08_platform_data	*pdata;
	int				status;
	int				do_update = 0;

	pdata = spi->dev.platform_data;
	if (!pdata || pdata->slave > 3 || !pdata->base)
		return -ENODEV;

	mcp = kzalloc(sizeof *mcp, GFP_KERNEL);
	if (!mcp)
		return -ENOMEM;

	mutex_init(&mcp->lock);

	mcp->spi = spi;
	mcp->addr = 0x40 | (pdata->slave << 1);

	mcp->chip.label = "mcp23s08",

	mcp->chip.direction_input = mcp23s08_direction_input;
	mcp->chip.get = mcp23s08_get;
	mcp->chip.direction_output = mcp23s08_direction_output;
	mcp->chip.set = mcp23s08_set;
	mcp->chip.dbg_show = mcp23s08_dbg_show;

	mcp->chip.base = pdata->base;
	mcp->chip.ngpio = 8;
	mcp->chip.can_sleep = 1;
	mcp->chip.owner = THIS_MODULE;

	spi_set_drvdata(spi, mcp);

	/* verify MCP_IOCON.SEQOP = 0, so sequential reads work */
	status = mcp23s08_read(mcp, MCP_IOCON);
	if (status < 0)
		goto fail;
	if (status & IOCON_SEQOP) {
		status &= ~IOCON_SEQOP;
		status = mcp23s08_write(mcp, MCP_IOCON, (u8) status);
		if (status < 0)
			goto fail;
	}

	/* configure ~100K pullups */
	status = mcp23s08_write(mcp, MCP_GPPU, pdata->pullups);
	if (status < 0)
		goto fail;

	status = mcp23s08_read_regs(mcp, 0, mcp->cache, sizeof mcp->cache);
	if (status < 0)
		goto fail;

	/* disable inverter on input */
	if (mcp->cache[MCP_IPOL] != 0) {
		mcp->cache[MCP_IPOL] = 0;
		do_update = 1;
	}

	/* disable irqs */
	if (mcp->cache[MCP_GPINTEN] != 0) {
		mcp->cache[MCP_GPINTEN] = 0;
		do_update = 1;
	}

	if (do_update) {
		u8 tx[4];

		tx[0] = mcp->addr;
		tx[1] = MCP_IPOL;
		memcpy(&tx[2], &mcp->cache[MCP_IPOL], sizeof(tx) - 2);
		status = spi_write_then_read(mcp->spi, tx, sizeof tx, NULL, 0);

		/* FIXME check status... */
	}

	status = gpiochip_add(&mcp->chip);

	/* NOTE:  these chips have a relatively sane IRQ framework, with
	 * per-signal masking and level/edge triggering.  It's not yet
	 * handled here...
	 */

	if (pdata->setup) {
		status = pdata->setup(spi, mcp->chip.base,
				mcp->chip.ngpio, pdata->context);
		if (status < 0)
			dev_dbg(&spi->dev, "setup --> %d\n", status);
	}

	return 0;

fail:
	kfree(mcp);
	return status;
}

static int mcp23s08_remove(struct spi_device *spi)
{
	struct mcp23s08			*mcp = spi_get_drvdata(spi);
	struct mcp23s08_platform_data	*pdata = spi->dev.platform_data;
	int				status = 0;

	if (pdata->teardown) {
		status = pdata->teardown(spi,
				mcp->chip.base, mcp->chip.ngpio,
				pdata->context);
		if (status < 0) {
			dev_err(&spi->dev, "%s --> %d\n", "teardown", status);
			return status;
		}
	}

	status = gpiochip_remove(&mcp->chip);
	if (status == 0)
		kfree(mcp);
	else
		dev_err(&spi->dev, "%s --> %d\n", "remove", status);
	return status;
}

static struct spi_driver mcp23s08_driver = {
	.probe		= mcp23s08_probe,
	.remove		= mcp23s08_remove,
	.driver = {
		.name	= "mcp23s08",
		.owner	= THIS_MODULE,
	},
};

/*----------------------------------------------------------------------*/

static int __init mcp23s08_init(void)
{
	return spi_register_driver(&mcp23s08_driver);
}
module_init(mcp23s08_init);

static void __exit mcp23s08_exit(void)
{
	spi_unregister_driver(&mcp23s08_driver);
}
module_exit(mcp23s08_exit);

MODULE_LICENSE("GPL");