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

[Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>]

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.ailus@xxxxxxxxxxxxxxx>
---
 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