/*
 * 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;

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

        struct gpio_chip        chip;

        struct work_struct      work;
};

/* A given spi_device can represent up to four mcp23s08 chips
 * sharing the same chipselect but using different addresses
 * (e.g. chips #0 and #3 might be populated, but not #1 or $2).
 * Driver data holds all the per-chip data.
 */
struct mcp23s08_driver_data {
        unsigned                ngpio;
        struct mcp23s08         *mcp[4];
        struct mcp23s08         chip[];
};

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_one(struct spi_device *spi, unsigned addr,
                unsigned base, unsigned pullups)
{
        struct mcp23s08_driver_data     *data = spi_get_drvdata(spi);
        struct mcp23s08                 *mcp = data->mcp[addr];
        int                             status;
        int                             do_update = 0;

        mutex_init(&mcp->lock);

        mcp->spi = spi;
        mcp->addr = 0x40 | (addr << 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 = base;
        mcp->chip.ngpio = 8;
        mcp->chip.can_sleep = 1;
        mcp->chip.dev = &spi->dev;
        mcp->chip.owner = THIS_MODULE;

        /* verify MCP_IOCON.SEQOP = 0, so sequential reads work,
         * and MCP_IOCON.HAEN = 1, so we work with all chips.
         */
        status = mcp23s08_read(mcp, MCP_IOCON);
        if (status < 0)
                goto fail;
        if ((status & IOCON_SEQOP) || !(status & IOCON_HAEN)) {
                status &= ~IOCON_SEQOP;
                status |= IOCON_HAEN;
                status = mcp23s08_write(mcp, MCP_IOCON, (u8) status);
                if (status < 0)
                        goto fail;
        }

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

        status = gpiochip_add(&mcp->chip);
fail:
        if (status < 0)
                dev_dbg(&spi->dev, "can't setup chip %d, --> %d\n",
                                addr, status);
        return status;
}

static int mcp23s08_probe(struct spi_device *spi)
{
        struct mcp23s08_platform_data   *pdata;
        unsigned                        addr;
        unsigned                        chips = 0;
        struct mcp23s08_driver_data     *data;
        int                             status;
        unsigned                        base;

        pdata = spi->dev.platform_data;
        if (!pdata || !gpio_is_valid(pdata->base)) {
                dev_dbg(&spi->dev, "invalid or missing platform data\n");
                return -EINVAL;
        }

        for (addr = 0; addr < 4; addr++) {
                if (!pdata->chip[addr].is_present)
                        continue;
                chips++;
        }
        if (!chips)
                return -ENODEV;

        data = kzalloc(sizeof *data + chips * sizeof(struct mcp23s08),
                        GFP_KERNEL);
        if (!data)
                return -ENOMEM;
        spi_set_drvdata(spi, data);

        base = pdata->base;
        for (addr = 0; addr < 4; addr++) {
                if (!pdata->chip[addr].is_present)
                        continue;
                chips--;
                data->mcp[addr] = &data->chip[chips];
                status = mcp23s08_probe_one(spi, addr, base,
                                pdata->chip[addr].pullups);
                if (status < 0)
                        goto fail;
                base += 8;
        }
        data->ngpio = base - pdata->base;

        /* 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,
                                pdata->base, data->ngpio,
                                pdata->context);
                if (status < 0)
                        dev_dbg(&spi->dev, "setup --> %d\n", status);
        }

        return 0;

fail:
        for (addr = 0; addr < 4; addr++) {
                int tmp;

                if (!data->mcp[addr])
                        continue;
                tmp = gpiochip_remove(&data->mcp[addr]->chip);
                if (tmp < 0)
                        dev_err(&spi->dev, "%s --> %d\n", "remove", tmp);
        }
        kfree(data);
        return status;
}

static int mcp23s08_remove(struct spi_device *spi)
{
        struct mcp23s08_driver_data     *data = spi_get_drvdata(spi);
        struct mcp23s08_platform_data   *pdata = spi->dev.platform_data;
        unsigned                        addr;
        int                             status = 0;

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

        for (addr = 0; addr < 4; addr++) {
                int tmp;

                if (!data->mcp[addr])
                        continue;

                tmp = gpiochip_remove(&data->mcp[addr]->chip);
                if (tmp < 0) {
                        dev_err(&spi->dev, "%s --> %d\n", "remove", tmp);
                        status = tmp;
                }
        }
        if (status == 0)
                kfree(data);
        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);
}
/* register after spi postcore initcall and before
 * subsys initcalls that may rely on these GPIOs
 */
subsys_initcall(mcp23s08_init);

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

MODULE_LICENSE("GPL");