i2c: gpio: Add support for deferred probing

GPIOs may not be available immediately when i2c-gpio looks for them.
Implement support for deferred probing so that probing can be
attempted again later when GPIO pins are finally available.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Tested-by: Bo Shen <voice.shen@atmel.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

1 files changed, 50 insertions, 25 deletions

diff --git a/drivers/i2c/busses/i2c-gpio.c b/drivers/i2c/busses/i2c-gpio.c
index f3fa4332bbdf..bc6e139c6e7f 100644
--- a/drivers/i2c/busses/i2c-gpio.c
+++ b/drivers/i2c/busses/i2c-gpio.c
@@ -85,23 +85,29 @@ static int i2c_gpio_getscl(void *data)
         return gpio_get_value(pdata->scl_pin);
 }
 
-static int of_i2c_gpio_probe(struct device_node *np,
-                             struct i2c_gpio_platform_data *pdata)
+static int of_i2c_gpio_get_pins(struct device_node *np,
+                                unsigned int *sda_pin, unsigned int *scl_pin)
 {
-        u32 reg;
-
         if (of_gpio_count(np) < 2)
                 return -ENODEV;
 
-        pdata->sda_pin = of_get_gpio(np, 0);
-        pdata->scl_pin = of_get_gpio(np, 1);
+        *sda_pin = of_get_gpio(np, 0);
+        *scl_pin = of_get_gpio(np, 1);
 
-        if (!gpio_is_valid(pdata->sda_pin) || !gpio_is_valid(pdata->scl_pin)) {
+        if (!gpio_is_valid(*sda_pin) || !gpio_is_valid(*scl_pin)) {
                 pr_err("%s: invalid GPIO pins, sda=%d/scl=%d\n",
-                       np->full_name, pdata->sda_pin, pdata->scl_pin);
+                       np->full_name, *sda_pin, *scl_pin);
                 return -ENODEV;
         }
 
+        return 0;
+}
+
+static void of_i2c_gpio_get_props(struct device_node *np,
+                                  struct i2c_gpio_platform_data *pdata)
+{
+        u32 reg;
+
         of_property_read_u32(np, "i2c-gpio,delay-us", &pdata->udelay);
 
         if (!of_property_read_u32(np, "i2c-gpio,timeout-ms", &reg))
@@ -113,8 +119,6 @@ static int of_i2c_gpio_probe(struct device_node *np,
                 of_property_read_bool(np, "i2c-gpio,scl-open-drain");
         pdata->scl_is_output_only =
                 of_property_read_bool(np, "i2c-gpio,scl-output-only");
-
-        return 0;
 }
 
 static int i2c_gpio_probe(struct platform_device *pdev)
@@ -123,31 +127,52 @@ static int i2c_gpio_probe(struct platform_device *pdev)
         struct i2c_gpio_platform_data *pdata;
         struct i2c_algo_bit_data *bit_data;
         struct i2c_adapter *adap;
+        unsigned int sda_pin, scl_pin;
         int ret;
 
-        priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
-        if (!priv)
-                return -ENOMEM;
-        adap = &priv->adap;
-        bit_data = &priv->bit_data;
-        pdata = &priv->pdata;
-
+        /* First get the GPIO pins; if it fails, we'll defer the probe. */
         if (pdev->dev.of_node) {
-                ret = of_i2c_gpio_probe(pdev->dev.of_node, pdata);
+                ret = of_i2c_gpio_get_pins(pdev->dev.of_node,
+                                           &sda_pin, &scl_pin);
                 if (ret)
                         return ret;
         } else {
                 if (!pdev->dev.platform_data)
                         return -ENXIO;
-                memcpy(pdata, pdev->dev.platform_data, sizeof(*pdata));
+                pdata = pdev->dev.platform_data;
+                sda_pin = pdata->sda_pin;
+                scl_pin = pdata->scl_pin;
         }
 
-        ret = gpio_request(pdata->sda_pin, "sda");
-        if (ret)
+        ret = gpio_request(sda_pin, "sda");
+        if (ret) {
+                if (ret == -EINVAL)
+                        ret = -EPROBE_DEFER;    /* Try again later */
                 goto err_request_sda;
-        ret = gpio_request(pdata->scl_pin, "scl");
-        if (ret)
+        }
+        ret = gpio_request(scl_pin, "scl");
+        if (ret) {
+                if (ret == -EINVAL)
+                        ret = -EPROBE_DEFER;    /* Try again later */
                 goto err_request_scl;
+        }
+
+        priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
+        if (!priv) {
+                ret = -ENOMEM;
+                goto err_add_bus;
+        }
+        adap = &priv->adap;
+        bit_data = &priv->bit_data;
+        pdata = &priv->pdata;
+
+        if (pdev->dev.of_node) {
+                pdata->sda_pin = sda_pin;
+                pdata->scl_pin = scl_pin;
+                of_i2c_gpio_get_props(pdev->dev.of_node, pdata);
+        } else {
+                memcpy(pdata, pdev->dev.platform_data, sizeof(*pdata));
+        }
 
         if (pdata->sda_is_open_drain) {
                 gpio_direction_output(pdata->sda_pin, 1);
@@ -211,9 +236,9 @@ static int i2c_gpio_probe(struct platform_device *pdev)
         return 0;
 
 err_add_bus:
-        gpio_free(pdata->scl_pin);
+        gpio_free(scl_pin);
 err_request_scl:
-        gpio_free(pdata->sda_pin);
+        gpio_free(sda_pin);
 err_request_sda:
         return ret;
 }