mcp23s08 spi gpio expander support

Basic driver for 8-bit SPI based MCP23S08 GPIO expander, without support for
IRQs or the shared chipselect mechanism.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Jean Delvare <khali@linux-fr.org>
Cc: Eric Miao <eric.miao@marvell.com>
Cc: Sam Ravnborg <sam@ravnborg.org>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: Philipp Zabel <philipp.zabel@gmail.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Ben Gardner <bgardner@wabtec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 389 insertions, 0 deletions

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 36d5d6aefc0e..d924a32c089a 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -52,4 +52,11 @@ config GPIO_PCF857X
 
 comment "SPI GPIO expanders:"
 
+config GPIO_MCP23S08
+        tristate "Microchip MCP23S08 I/O expander"
+        depends on SPI_MASTER
+        help
+          SPI driver for Microchip MCP23S08 I/O expander.  This provides
+          a GPIO interface supporting inputs and outputs.
+
 endmenu
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index b469ab24fb11..a1fd877ac527 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -4,4 +4,5 @@ ccflags-$(CONFIG_DEBUG_GPIO)	+= -DDEBUG
 
 obj-$(CONFIG_HAVE_GPIO_LIB)     += gpiolib.o
 
+obj-$(CONFIG_GPIO_MCP23S08)     += mcp23s08.o
 obj-$(CONFIG_GPIO_PCF857X)      += pcf857x.o
diff --git a/drivers/gpio/mcp23s08.c b/drivers/gpio/mcp23s08.c
new file mode 100644
index 000000000000..bb60e8c1a1f0
--- /dev/null
+++ b/drivers/gpio/mcp23s08.c
@@ -0,0 +1,357 @@
+/*
+ * 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;
+        unsigned        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;
+
+        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");
+
diff --git a/include/linux/spi/mcp23s08.h b/include/linux/spi/mcp23s08.h
new file mode 100644
index 000000000000..835ddf47d45c
--- /dev/null
+++ b/include/linux/spi/mcp23s08.h
@@ -0,0 +1,24 @@
+
+/* FIXME driver should be able to handle all four slaves that
+ * can be hooked up to each chipselect, as well as IRQs...
+ */
+
+struct mcp23s08_platform_data {
+        /* four slaves can share one SPI chipselect */
+        u8              slave;
+
+        /* number assigned to the first GPIO */
+        unsigned        base;
+
+        /* pins with pullups */
+        u8              pullups;
+
+        void            *context;       /* param to setup/teardown */
+
+        int             (*setup)(struct spi_device *spi,
+                                        int gpio, unsigned ngpio,
+                                        void *context);
+        int             (*teardown)(struct spi_device *spi,
+                                        int gpio, unsigned ngpio,
+                                        void *context);
+};