leds: pca955x: add GPIO support

The PCA955x family of chips are I2C LED blinkers whose pins not used
to control LEDs can be used as general purpose I/Os (GPIOs).

The following adds such a support by defining different operation
modes for the pins (See bindings documentation for more details). The
pca955x driver is then extended with a gpio_chip when some of pins are
operating as GPIOs. The default operating mode is to behave as a LED.

The GPIO support is conditioned by CONFIG_LEDS_PCA955X_GPIO.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Acked-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Jacek Anaszewski <jacek.anaszewski@gmail.com>

2 files changed, 131 insertions, 17 deletions

diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index 594b24d410c3..3013cd35c65e 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -377,6 +377,17 @@ config LEDS_PCA955X
           LED driver chips accessed via the I2C bus.  Supported
           devices include PCA9550, PCA9551, PCA9552, and PCA9553.
 
+config LEDS_PCA955X_GPIO
+        bool "Enable GPIO support for PCA955X"
+        depends on LEDS_PCA955X
+        depends on GPIOLIB
+        help
+          Allow unused pins on PCA955X to be used as gpio.
+
+          To use a pin as gpio the pin type should be set to
+          PCA955X_TYPE_GPIO in the device tree.
+
+
 config LEDS_PCA963X
         tristate "LED support for PCA963x I2C chip"
         depends on LEDS_CLASS
diff --git a/drivers/leds/leds-pca955x.c b/drivers/leds/leds-pca955x.c
index 5a5d3765cfd3..f062d1e7640f 100644
--- a/drivers/leds/leds-pca955x.c
+++ b/drivers/leds/leds-pca955x.c
@@ -53,6 +53,8 @@
 #include <linux/slab.h>
 #include <linux/string.h>
 
+#include <dt-bindings/leds/leds-pca955x.h>
+
 /* LED select registers determine the source that drives LED outputs */
 #define PCA955X_LS_LED_ON       0x0     /* Output LOW */
 #define PCA955X_LS_LED_OFF      0x1     /* Output HI-Z */
@@ -118,6 +120,9 @@ struct pca955x {
         struct pca955x_led *leds;
         struct pca955x_chipdef  *chipdef;
         struct i2c_client       *client;
+#ifdef CONFIG_LEDS_PCA955X_GPIO
+        struct gpio_chip gpio;
+#endif
 };
 
 struct pca955x_led {
@@ -125,6 +130,7 @@ struct pca955x_led {
         struct led_classdev     led_cdev;
         int                     led_num;        /* 0 .. 15 potentially */
         char                    name[32];
+        u32                     type;
         const char              *default_trigger;
 };
 
@@ -259,6 +265,65 @@ static int pca955x_led_set(struct led_classdev *led_cdev,
         return 0;
 }
 
+#ifdef CONFIG_LEDS_PCA955X_GPIO
+/*
+ * Read the INPUT register, which contains the state of LEDs.
+ */
+static u8 pca955x_read_input(struct i2c_client *client, int n)
+{
+        return (u8)i2c_smbus_read_byte_data(client, n);
+}
+
+static int pca955x_gpio_request_pin(struct gpio_chip *gc, unsigned int offset)
+{
+        struct pca955x *pca955x = gpiochip_get_data(gc);
+        struct pca955x_led *led = &pca955x->leds[offset];
+
+        if (led->type == PCA955X_TYPE_GPIO)
+                return 0;
+
+        return -EBUSY;
+}
+
+static void pca955x_gpio_set_value(struct gpio_chip *gc, unsigned int offset,
+                                   int val)
+{
+        struct pca955x *pca955x = gpiochip_get_data(gc);
+        struct pca955x_led *led = &pca955x->leds[offset];
+
+        if (val)
+                pca955x_led_set(&led->led_cdev, LED_FULL);
+        else
+                pca955x_led_set(&led->led_cdev, LED_OFF);
+}
+
+static int pca955x_gpio_get_value(struct gpio_chip *gc, unsigned int offset)
+{
+        struct pca955x *pca955x = gpiochip_get_data(gc);
+        struct pca955x_led *led = &pca955x->leds[offset];
+        u8 reg = pca955x_read_input(pca955x->client, led->led_num / 8);
+
+        return !!(reg & (1 << (led->led_num % 8)));
+}
+
+static int pca955x_gpio_direction_input(struct gpio_chip *gc,
+                                        unsigned int offset)
+{
+        /* To use as input ensure pin is not driven */
+        pca955x_gpio_set_value(gc, offset, 0);
+
+        return 0;
+}
+
+static int pca955x_gpio_direction_output(struct gpio_chip *gc,
+                                         unsigned int offset, int val)
+{
+        pca955x_gpio_set_value(gc, offset, val);
+
+        return 0;
+}
+#endif /* CONFIG_LEDS_PCA955X_GPIO */
+
 #if IS_ENABLED(CONFIG_OF)
 static struct pca955x_platform_data *
 pca955x_pdata_of_init(struct i2c_client *client, struct pca955x_chipdef *chip)
@@ -297,6 +362,8 @@ pca955x_pdata_of_init(struct i2c_client *client, struct pca955x_chipdef *chip)
                 snprintf(pdata->leds[reg].name, sizeof(pdata->leds[reg].name),
                          "%s", name);
 
+                pdata->leds[reg].type = PCA955X_TYPE_LED;
+                of_property_read_u32(child, "type", &pdata->leds[reg].type);
                 of_property_read_string(child, "linux,default-trigger",
                                         &pdata->leds[reg].default_trigger);
         }
@@ -332,6 +399,7 @@ static int pca955x_probe(struct i2c_client *client,
         struct i2c_adapter *adapter;
         int i, err;
         struct pca955x_platform_data *pdata;
+        int ngpios = 0;
 
         if (id) {
                 chip = &pca955x_chipdefs[id->driver_data];
@@ -392,9 +460,19 @@ static int pca955x_probe(struct i2c_client *client,
                 pca955x_led = &pca955x->leds[i];
                 pca955x_led->led_num = i;
                 pca955x_led->pca955x = pca955x;
-
-                /* Platform data can specify LED names and default triggers */
-                if (pdata) {
+                pca955x_led->type = pdata->leds[i].type;
+
+                switch (pca955x_led->type) {
+                case PCA955X_TYPE_NONE:
+                        break;
+                case PCA955X_TYPE_GPIO:
+                        ngpios++;
+                        break;
+                case PCA955X_TYPE_LED:
+                        /*
+                         * Platform data can specify LED names and
+                         * default triggers
+                         */
                         if (pdata->leds[i].name)
                                 snprintf(pca955x_led->name,
                                         sizeof(pca955x_led->name), "pca955x:%s",
@@ -402,23 +480,20 @@ static int pca955x_probe(struct i2c_client *client,
                         if (pdata->leds[i].default_trigger)
                                 pca955x_led->led_cdev.default_trigger =
                                         pdata->leds[i].default_trigger;
-                } else {
-                        snprintf(pca955x_led->name, sizeof(pca955x_led->name),
-                                 "pca955x:%d", i);
-                }
 
-                pca955x_led->led_cdev.name = pca955x_led->name;
-                pca955x_led->led_cdev.brightness_set_blocking = pca955x_led_set;
+                        pca955x_led->led_cdev.name = pca955x_led->name;
+                        pca955x_led->led_cdev.brightness_set_blocking =
+                                pca955x_led_set;
 
-                err = devm_led_classdev_register(&client->dev,
-                                                 &pca955x_led->led_cdev);
-                if (err)
-                        return err;
-        }
+                        err = devm_led_classdev_register(&client->dev,
+                                                        &pca955x_led->led_cdev);
+                        if (err)
+                                return err;
 
-        /* Turn off LEDs */
-        for (i = 0; i < pca95xx_num_led_regs(chip->bits); i++)
-                pca955x_write_ls(client, i, 0x55);
+                        /* Turn off LED */
+                        pca955x_led_set(&pca955x_led->led_cdev, LED_OFF);
+                }
+        }
 
         /* PWM0 is used for half brightness or 50% duty cycle */
         pca955x_write_pwm(client, 0, 255-LED_HALF);
@@ -430,6 +505,34 @@ static int pca955x_probe(struct i2c_client *client,
         pca955x_write_psc(client, 0, 0);
         pca955x_write_psc(client, 1, 0);
 
+#ifdef CONFIG_LEDS_PCA955X_GPIO
+        if (ngpios) {
+                pca955x->gpio.label = "gpio-pca955x";
+                pca955x->gpio.direction_input = pca955x_gpio_direction_input;
+                pca955x->gpio.direction_output = pca955x_gpio_direction_output;
+                pca955x->gpio.set = pca955x_gpio_set_value;
+                pca955x->gpio.get = pca955x_gpio_get_value;
+                pca955x->gpio.request = pca955x_gpio_request_pin;
+                pca955x->gpio.can_sleep = 1;
+                pca955x->gpio.base = -1;
+                pca955x->gpio.ngpio = ngpios;
+                pca955x->gpio.parent = &client->dev;
+                pca955x->gpio.owner = THIS_MODULE;
+
+                err = devm_gpiochip_add_data(&client->dev, &pca955x->gpio,
+                                             pca955x);
+                if (err) {
+                        /* Use data->gpio.dev as a flag for freeing gpiochip */
+                        pca955x->gpio.parent = NULL;
+                        dev_warn(&client->dev, "could not add gpiochip\n");
+                        return err;
+                }
+                dev_info(&client->dev, "gpios %i...%i\n",
+                         pca955x->gpio.base, pca955x->gpio.base +
+                         pca955x->gpio.ngpio - 1);
+        }
+#endif
+
         return 0;
 }