[PATCH v8 4/6] ov5670: Support probe whilst the device is in a low power state

[Sakari Ailus]

Tell ACPI device PM code that the driver supports the device being in a
low power state when the driver's probe function is entered.

Also do identification on the first access of the device, whether in probe
or when starting streaming.

Signed-off-by: Sakari Ailus <sakari.ai...@linux.intel.com>
---
 drivers/media/i2c/ov5670.c | 76 +++++++++++++++++++++++---------------
 1 file changed, 46 insertions(+), 30 deletions(-)

diff --git a/drivers/media/i2c/ov5670.c b/drivers/media/i2c/ov5670.c
index f26252e35e08d..74b0325c22565 100644
--- a/drivers/media/i2c/ov5670.c
+++ b/drivers/media/i2c/ov5670.c
@@ -1832,6 +1832,8 @@ struct ov5670 {
 
        /* Streaming on/off */
        bool streaming;
+       /* True if the device has been identified */
+       bool identified;
 };
 
 #define to_ov5670(_sd) container_of(_sd, struct ov5670, sd)
@@ -2270,6 +2272,32 @@ static int ov5670_get_skip_frames(struct v4l2_subdev 
*sd, u32 *frames)
        return 0;
 }
 
+/* Verify chip ID */
+static int ov5670_identify_module(struct ov5670 *ov5670)
+{
+       struct i2c_client *client = v4l2_get_subdevdata(&ov5670->sd);
+       int ret;
+       u32 val;
+
+       if (ov5670->identified)
+               return 0;
+
+       ret = ov5670_read_reg(ov5670, OV5670_REG_CHIP_ID,
+                             OV5670_REG_VALUE_24BIT, &val);
+       if (ret)
+               return ret;
+
+       if (val != OV5670_CHIP_ID) {
+               dev_err(&client->dev, "chip id mismatch: %x!=%x\n",
+                       OV5670_CHIP_ID, val);
+               return -ENXIO;
+       }
+
+       ov5670->identified = true;
+
+       return 0;
+}
+
 /* Prepare streaming by writing default values and customized values */
 static int ov5670_start_streaming(struct ov5670 *ov5670)
 {
@@ -2278,6 +2306,10 @@ static int ov5670_start_streaming(struct ov5670 *ov5670)
        int link_freq_index;
        int ret;
 
+       ret = ov5670_identify_module(ov5670);
+       if (ret)
+               return ret;
+
        /* Get out of from software reset */
        ret = ov5670_write_reg(ov5670, OV5670_REG_SOFTWARE_RST,
                               OV5670_REG_VALUE_08BIT, OV5670_SOFTWARE_RST);
@@ -2401,27 +2433,6 @@ static int __maybe_unused ov5670_resume(struct device 
*dev)
        return 0;
 }
 
-/* Verify chip ID */
-static int ov5670_identify_module(struct ov5670 *ov5670)
-{
-       struct i2c_client *client = v4l2_get_subdevdata(&ov5670->sd);
-       int ret;
-       u32 val;
-
-       ret = ov5670_read_reg(ov5670, OV5670_REG_CHIP_ID,
-                             OV5670_REG_VALUE_24BIT, &val);
-       if (ret)
-               return ret;
-
-       if (val != OV5670_CHIP_ID) {
-               dev_err(&client->dev, "chip id mismatch: %x!=%x\n",
-                       OV5670_CHIP_ID, val);
-               return -ENXIO;
-       }
-
-       return 0;
-}
-
 static const struct v4l2_subdev_video_ops ov5670_video_ops = {
        .s_stream = ov5670_set_stream,
 };
@@ -2456,6 +2467,7 @@ static int ov5670_probe(struct i2c_client *client)
        struct ov5670 *ov5670;
        const char *err_msg;
        u32 input_clk = 0;
+       bool low_power;
        int ret;
 
        device_property_read_u32(&client->dev, "clock-frequency", &input_clk);
@@ -2472,11 +2484,14 @@ static int ov5670_probe(struct i2c_client *client)
        /* Initialize subdev */
        v4l2_i2c_subdev_init(&ov5670->sd, client, &ov5670_subdev_ops);
 
-       /* Check module identity */
-       ret = ov5670_identify_module(ov5670);
-       if (ret) {
-               err_msg = "ov5670_identify_module() error";
-               goto error_print;
+       low_power = acpi_dev_state_low_power(&client->dev);
+       if (!low_power) {
+               /* Check module identity */
+               ret = ov5670_identify_module(ov5670);
+               if (ret) {
+                       err_msg = "ov5670_identify_module() error";
+                       goto error_print;
+               }
        }
 
        mutex_init(&ov5670->mutex);
@@ -2513,10 +2528,10 @@ static int ov5670_probe(struct i2c_client *client)
        ov5670->streaming = false;
 
        /*
-        * Device is already turned on by i2c-core with ACPI domain PM.
-        * Enable runtime PM and turn off the device.
+        * Don't set the device's state to active if it's in a low power state.
         */
-       pm_runtime_set_active(&client->dev);
+       if (!low_power)
+               pm_runtime_set_active(&client->dev);
        pm_runtime_enable(&client->dev);
        pm_runtime_idle(&client->dev);
 
@@ -2558,7 +2573,7 @@ static const struct dev_pm_ops ov5670_pm_ops = {
 
 #ifdef CONFIG_ACPI
 static const struct acpi_device_id ov5670_acpi_ids[] = {
-       {"INT3479"},
+       { "INT3479" },
        { /* sentinel */ }
 };
 
@@ -2573,6 +2588,7 @@ static struct i2c_driver ov5670_i2c_driver = {
        },
        .probe_new = ov5670_probe,
        .remove = ov5670_remove,
+       .flags = I2C_DRV_FL_ALLOW_LOW_POWER_PROBE,
 };
 
 module_i2c_driver(ov5670_i2c_driver);
-- 
2.20.1