gpio: pca953x.c: add interrupt handling capability

Most of the GPIO expanders controlled by the pca953x driver are able to
report changes on the input pins through an *INT pin.

This patch implements the irq_chip functionality (edge detection only).

The driver has been tested on an Arcom Zeus.

[akpm@linux-foundation.org: the compiler does inlining for us nowadays]
Signed-off-by: Marc Zyngier <maz@misterjones.org>
Cc: Eric Miao <eric.y.miao@gmail.com>
Cc: Haojian Zhuang <haojian.zhuang@gmail.com>
Cc: David Brownell <david-b@pacbell.net>
Cc: Nate Case <ncase@xes-inc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 247 insertions, 12 deletions

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index f3549b8779d8..c5cc7d9d88e3 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -134,6 +134,13 @@ config GPIO_PCA953X
           This driver can also be built as a module.  If so, the module
           will be called pca953x.
 
+config GPIO_PCA953X_IRQ
+        bool "Interrupt controller support for PCA953x"
+        depends on GPIO_PCA953X=y
+        help
+          Say yes here to enable the pca953x to be used as an interrupt
+          controller. It requires the driver to be built in the kernel.
+
 config GPIO_PCF857X
         tristate "PCF857x, PCA{85,96}7x, and MAX732[89] I2C GPIO expanders"
         depends on I2C
diff --git a/drivers/gpio/pca953x.c b/drivers/gpio/pca953x.c
index 6a2fb3fbb3d9..ab5daab14bc2 100644
--- a/drivers/gpio/pca953x.c
+++ b/drivers/gpio/pca953x.c
@@ -14,6 +14,8 @@
 #include <linux/module.h>
 #include <linux/init.h>
 #include <linux/gpio.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
 #include <linux/i2c.h>
 #include <linux/i2c/pca953x.h>
 #ifdef CONFIG_OF_GPIO
@@ -26,23 +28,28 @@
 #define PCA953X_INVERT         2
 #define PCA953X_DIRECTION      3
 
+#define PCA953X_GPIOS          0x00FF
+#define PCA953X_INT            0x0100
+
 static const struct i2c_device_id pca953x_id[] = {
-        { "pca9534", 8, },
-        { "pca9535", 16, },
+        { "pca9534", 8  | PCA953X_INT, },
+        { "pca9535", 16 | PCA953X_INT, },
         { "pca9536", 4, },
-        { "pca9537", 4, },
-        { "pca9538", 8, },
-        { "pca9539", 16, },
-        { "pca9554", 8, },
-        { "pca9555", 16, },
+        { "pca9537", 4  | PCA953X_INT, },
+        { "pca9538", 8  | PCA953X_INT, },
+        { "pca9539", 16 | PCA953X_INT, },
+        { "pca9554", 8  | PCA953X_INT, },
+        { "pca9555", 16 | PCA953X_INT, },
         { "pca9556", 8, },
         { "pca9557", 8, },
 
         { "max7310", 8, },
-        { "max7315", 8, },
-        { "pca6107", 8, },
-        { "tca6408", 8, },
-        { "tca6416", 16, },
+        { "max7312", 16 | PCA953X_INT, },
+        { "max7313", 16 | PCA953X_INT, },
+        { "max7315", 8  | PCA953X_INT, },
+        { "pca6107", 8  | PCA953X_INT, },
+        { "tca6408", 8  | PCA953X_INT, },
+        { "tca6416", 16 | PCA953X_INT, },
         /* NYET:  { "tca6424", 24, }, */
         { }
 };
@@ -53,6 +60,15 @@ struct pca953x_chip {
         uint16_t reg_output;
         uint16_t reg_direction;
 
+#ifdef CONFIG_GPIO_PCA953X_IRQ
+        struct mutex irq_lock;
+        uint16_t irq_mask;
+        uint16_t irq_stat;
+        uint16_t irq_trig_raise;
+        uint16_t irq_trig_fall;
+        int      irq_base;
+#endif
+
         struct i2c_client *client;
         struct pca953x_platform_data *dyn_pdata;
         struct gpio_chip gpio_chip;
@@ -202,6 +218,210 @@ static void pca953x_setup_gpio(struct pca953x_chip *chip, int gpios)
         gc->names = chip->names;
 }
 
+#ifdef CONFIG_GPIO_PCA953X_IRQ
+static int pca953x_gpio_to_irq(struct gpio_chip *gc, unsigned off)
+{
+        struct pca953x_chip *chip;
+
+        chip = container_of(gc, struct pca953x_chip, gpio_chip);
+        return chip->irq_base + off;
+}
+
+static void pca953x_irq_mask(unsigned int irq)
+{
+        struct pca953x_chip *chip = get_irq_chip_data(irq);
+
+        chip->irq_mask &= ~(1 << (irq - chip->irq_base));
+}
+
+static void pca953x_irq_unmask(unsigned int irq)
+{
+        struct pca953x_chip *chip = get_irq_chip_data(irq);
+
+        chip->irq_mask |= 1 << (irq - chip->irq_base);
+}
+
+static void pca953x_irq_bus_lock(unsigned int irq)
+{
+        struct pca953x_chip *chip = get_irq_chip_data(irq);
+
+        mutex_lock(&chip->irq_lock);
+}
+
+static void pca953x_irq_bus_sync_unlock(unsigned int irq)
+{
+        struct pca953x_chip *chip = get_irq_chip_data(irq);
+
+        mutex_unlock(&chip->irq_lock);
+}
+
+static int pca953x_irq_set_type(unsigned int irq, unsigned int type)
+{
+        struct pca953x_chip *chip = get_irq_chip_data(irq);
+        uint16_t level = irq - chip->irq_base;
+        uint16_t mask = 1 << level;
+
+        if (!(type & IRQ_TYPE_EDGE_BOTH)) {
+                dev_err(&chip->client->dev, "irq %d: unsupported type %d\n",
+                        irq, type);
+                return -EINVAL;
+        }
+
+        if (type & IRQ_TYPE_EDGE_FALLING)
+                chip->irq_trig_fall |= mask;
+        else
+                chip->irq_trig_fall &= ~mask;
+
+        if (type & IRQ_TYPE_EDGE_RISING)
+                chip->irq_trig_raise |= mask;
+        else
+                chip->irq_trig_raise &= ~mask;
+
+        return pca953x_gpio_direction_input(&chip->gpio_chip, level);
+}
+
+static struct irq_chip pca953x_irq_chip = {
+        .name                   = "pca953x",
+        .mask                   = pca953x_irq_mask,
+        .unmask                 = pca953x_irq_unmask,
+        .bus_lock               = pca953x_irq_bus_lock,
+        .bus_sync_unlock        = pca953x_irq_bus_sync_unlock,
+        .set_type               = pca953x_irq_set_type,
+};
+
+static uint16_t pca953x_irq_pending(struct pca953x_chip *chip)
+{
+        uint16_t cur_stat;
+        uint16_t old_stat;
+        uint16_t pending;
+        uint16_t trigger;
+        int ret;
+
+        ret = pca953x_read_reg(chip, PCA953X_INPUT, &cur_stat);
+        if (ret)
+                return 0;
+
+        /* Remove output pins from the equation */
+        cur_stat &= chip->reg_direction;
+
+        old_stat = chip->irq_stat;
+        trigger = (cur_stat ^ old_stat) & chip->irq_mask;
+
+        if (!trigger)
+                return 0;
+
+        chip->irq_stat = cur_stat;
+
+        pending = (old_stat & chip->irq_trig_fall) |
+                  (cur_stat & chip->irq_trig_raise);
+        pending &= trigger;
+
+        return pending;
+}
+
+static irqreturn_t pca953x_irq_handler(int irq, void *devid)
+{
+        struct pca953x_chip *chip = devid;
+        uint16_t pending;
+        uint16_t level;
+
+        pending = pca953x_irq_pending(chip);
+
+        if (!pending)
+                return IRQ_HANDLED;
+
+        do {
+                level = __ffs(pending);
+                handle_nested_irq(level + chip->irq_base);
+
+                pending &= ~(1 << level);
+        } while (pending);
+
+        return IRQ_HANDLED;
+}
+
+static int pca953x_irq_setup(struct pca953x_chip *chip,
+                             const struct i2c_device_id *id)
+{
+        struct i2c_client *client = chip->client;
+        struct pca953x_platform_data *pdata = client->dev.platform_data;
+        int ret;
+
+        if (pdata->irq_base && (id->driver_data & PCA953X_INT)) {
+                int lvl;
+
+                ret = pca953x_read_reg(chip, PCA953X_INPUT,
+                                       &chip->irq_stat);
+                if (ret)
+                        goto out_failed;
+
+                /*
+                 * There is no way to know which GPIO line generated the
+                 * interrupt.  We have to rely on the previous read for
+                 * this purpose.
+                 */
+                chip->irq_stat &= chip->reg_direction;
+                chip->irq_base = pdata->irq_base;
+                mutex_init(&chip->irq_lock);
+
+                for (lvl = 0; lvl < chip->gpio_chip.ngpio; lvl++) {
+                        int irq = lvl + chip->irq_base;
+
+                        set_irq_chip_data(irq, chip);
+                        set_irq_chip_and_handler(irq, &pca953x_irq_chip,
+                                                 handle_edge_irq);
+                        set_irq_nested_thread(irq, 1);
+#ifdef CONFIG_ARM
+                        set_irq_flags(irq, IRQF_VALID);
+#else
+                        set_irq_noprobe(irq);
+#endif
+                }
+
+                ret = request_threaded_irq(client->irq,
+                                           NULL,
+                                           pca953x_irq_handler,
+                                           IRQF_TRIGGER_FALLING | IRQF_ONESHOT,
+                                           dev_name(&client->dev), chip);
+                if (ret) {
+                        dev_err(&client->dev, "failed to request irq %d\n",
+                                client->irq);
+                        goto out_failed;
+                }
+
+                chip->gpio_chip.to_irq = pca953x_gpio_to_irq;
+        }
+
+        return 0;
+
+out_failed:
+        chip->irq_base = 0;
+        return ret;
+}
+
+static void pca953x_irq_teardown(struct pca953x_chip *chip)
+{
+        if (chip->irq_base)
+                free_irq(chip->client->irq, chip);
+}
+#else /* CONFIG_GPIO_PCA953X_IRQ */
+static int pca953x_irq_setup(struct pca953x_chip *chip,
+                             const struct i2c_device_id *id)
+{
+        struct i2c_client *client = chip->client;
+        struct pca953x_platform_data *pdata = client->dev.platform_data;
+
+        if (pdata->irq_base && (id->driver_data & PCA953X_INT))
+                dev_warn(&client->dev, "interrupt support not compiled in\n");
+
+        return 0;
+}
+
+static void pca953x_irq_teardown(struct pca953x_chip *chip)
+{
+}
+#endif
+
 /*
  * Handlers for alternative sources of platform_data
  */
@@ -286,7 +506,7 @@ static int __devinit pca953x_probe(struct i2c_client *client,
         /* initialize cached registers from their original values.
          * we can't share this chip with another i2c master.
          */
-        pca953x_setup_gpio(chip, id->driver_data);
+        pca953x_setup_gpio(chip, id->driver_data & PCA953X_GPIOS);
 
         ret = pca953x_read_reg(chip, PCA953X_OUTPUT, &chip->reg_output);
         if (ret)
@@ -301,6 +521,9 @@ static int __devinit pca953x_probe(struct i2c_client *client,
         if (ret)
                 goto out_failed;
 
+        ret = pca953x_irq_setup(chip, id);
+        if (ret)
+                goto out_failed;
 
         ret = gpiochip_add(&chip->gpio_chip);
         if (ret)
@@ -317,6 +540,7 @@ static int __devinit pca953x_probe(struct i2c_client *client,
         return 0;
 
 out_failed:
+        pca953x_irq_teardown(chip);
         kfree(chip->dyn_pdata);
         kfree(chip);
         return ret;
@@ -345,6 +569,7 @@ static int pca953x_remove(struct i2c_client *client)
                 return ret;
         }
 
+        pca953x_irq_teardown(chip);
         kfree(chip->dyn_pdata);
         kfree(chip);
         return 0;
diff --git a/include/linux/i2c/pca953x.h b/include/linux/i2c/pca953x.h
index 29699f8dc5a4..d5c5a60c8a0b 100644
--- a/include/linux/i2c/pca953x.h
+++ b/include/linux/i2c/pca953x.h
@@ -13,6 +13,9 @@ struct pca953x_platform_data {
         /* initial polarity inversion setting */
         uint16_t        invert;
 
+        /* interrupt base */
+        int             irq_base;
+
         void            *context;       /* param to setup/teardown */
 
         int             (*setup)(struct i2c_client *client,