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>

diff --git a/drivers/i2c/busses/i2c-gpio.c b/drivers/i2c/busses/i2c-gpio.c
index f3fa4332bbdf9fa93ad497002fee91ab858d06ee..bc6e139c6e7f3f6b91e1f054c7569a5191a08b9a 100644 (file)
--- 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;
 }