[PATCH 3/4] media: i2c: ov9734: Add reset GPIO, supplies and PM callbacks

[Afonso Figuinha <afonso.figuinha@gmail.com>]

The driver relies on ACPI to power the sensor. On the Microsoft Surface
Laptop 1 an INT3472 discrete device controls the sensor clock and reset
line instead, so the sensor stays in reset and probe fails when reading
the chip ID.

Request the optional reset GPIO and the dovdd, avdd and dvdd supplies,
enable the clock, and add runtime PM callbacks that power the sensor on
and off. Power the sensor on in probe before identifying it. Call
pm_runtime_idle() only once the subdev is registered, so the probe
error path does not power the sensor off twice.

The INT3472 on the Surface Laptop 1 provides no supplies, so they fall
back to dummy regulators there. On platforms where ACPI powers the
sensor and no reset GPIO is described, the callbacks only enable and
disable the clock.

The public OV9734 documentation does not give power-up timings. The
2 ms wait before releasing reset and the 6 ms wait after it were chosen
empirically and work on the Surface Laptop 1.

The change and this description were drafted with an AI coding
assistant (Claude Code, model Claude Opus 5.5). The author reviewed
them and tested them on a Microsoft Surface Laptop 1.

Signed-off-by: Afonso Figuinha <afonso.figuinha@gmail.com>
---
 drivers/media/i2c/ov9734.c | 93 ++++++++++++++++++++++++++++++++++++--
 1 file changed, 89 insertions(+), 4 deletions(-)

diff --git a/drivers/media/i2c/ov9734.c b/drivers/media/i2c/ov9734.c
index 5f3e277b9..bf19ea56f 100644
--- a/drivers/media/i2c/ov9734.c
+++ b/drivers/media/i2c/ov9734.c
@@ -4,9 +4,11 @@
 #include <linux/acpi.h>
 #include <linux/clk.h>
 #include <linux/delay.h>
+#include <linux/gpio/consumer.h>
 #include <linux/i2c.h>
 #include <linux/module.h>
 #include <linux/pm_runtime.h>
+#include <linux/regulator/consumer.h>
 #include <linux/unaligned.h>
 
 #include <media/v4l2-ctrls.h>
@@ -322,9 +324,17 @@ static const struct ov9734_mode supported_modes[] = {
 	},
 };
 
+static const char * const ov9734_supply_names[] = {
+	"dovdd",	/* Digital I/O power */
+	"avdd",		/* Analog power */
+	"dvdd",		/* Digital core power */
+};
+
 struct ov9734 {
 	struct device *dev;
 	struct clk *clk;
+	struct gpio_desc *reset;
+	struct regulator_bulk_data supplies[ARRAY_SIZE(ov9734_supply_names)];
 
 	struct v4l2_subdev sd;
 	struct media_pad pad;
@@ -824,6 +834,51 @@ static int ov9734_identify_module(struct ov9734 *ov9734)
 	return 0;
 }
 
+static int ov9734_power_on(struct device *dev)
+{
+	struct v4l2_subdev *sd = dev_get_drvdata(dev);
+	struct ov9734 *ov9734 = to_ov9734(sd);
+	int ret;
+
+	ret = clk_prepare_enable(ov9734->clk);
+	if (ret) {
+		dev_err(dev, "failed to enable clock: %d\n", ret);
+		return ret;
+	}
+
+	ret = regulator_bulk_enable(ARRAY_SIZE(ov9734_supply_names),
+				    ov9734->supplies);
+	if (ret) {
+		dev_err(dev, "failed to enable regulators: %d\n", ret);
+		clk_disable_unprepare(ov9734->clk);
+		return ret;
+	}
+
+	if (ov9734->reset) {
+		fsleep(2000);
+		gpiod_set_value_cansleep(ov9734->reset, 0);
+		fsleep(6000);
+	}
+
+	return 0;
+}
+
+static int ov9734_power_off(struct device *dev)
+{
+	struct v4l2_subdev *sd = dev_get_drvdata(dev);
+	struct ov9734 *ov9734 = to_ov9734(sd);
+
+	gpiod_set_value_cansleep(ov9734->reset, 1);
+	regulator_bulk_disable(ARRAY_SIZE(ov9734_supply_names),
+			       ov9734->supplies);
+	clk_disable_unprepare(ov9734->clk);
+
+	return 0;
+}
+
+static DEFINE_RUNTIME_DEV_PM_OPS(ov9734_pm_ops, ov9734_power_off,
+				 ov9734_power_on, NULL);
+
 static int ov9734_check_hwcfg(struct device *dev)
 {
 	struct fwnode_handle *ep;
@@ -887,6 +942,8 @@ static void ov9734_remove(struct i2c_client *client)
 	media_entity_cleanup(&sd->entity);
 	v4l2_ctrl_handler_free(sd->ctrl_handler);
 	pm_runtime_disable(ov9734->dev);
+	if (!pm_runtime_status_suspended(ov9734->dev))
+		ov9734_power_off(ov9734->dev);
 	pm_runtime_set_suspended(ov9734->dev);
 	mutex_destroy(&ov9734->mutex);
 }
@@ -895,6 +952,7 @@ static int ov9734_probe(struct i2c_client *client)
 {
 	struct ov9734 *ov9734;
 	unsigned long freq;
+	unsigned int i;
 	int ret;
 
 	ret = ov9734_check_hwcfg(&client->dev);
@@ -918,11 +976,32 @@ static int ov9734_probe(struct i2c_client *client)
 				     "external clock %lu is not supported",
 				     freq);
 
+	ov9734->reset = devm_gpiod_get_optional(ov9734->dev, "reset",
+						GPIOD_OUT_HIGH);
+	if (IS_ERR(ov9734->reset))
+		return dev_err_probe(ov9734->dev, PTR_ERR(ov9734->reset),
+				     "failed to get reset GPIO\n");
+
+	for (i = 0; i < ARRAY_SIZE(ov9734_supply_names); i++)
+		ov9734->supplies[i].supply = ov9734_supply_names[i];
+
+	ret = devm_regulator_bulk_get(ov9734->dev,
+				      ARRAY_SIZE(ov9734_supply_names),
+				      ov9734->supplies);
+	if (ret)
+		return dev_err_probe(ov9734->dev, ret,
+				     "failed to get regulators\n");
+
 	v4l2_i2c_subdev_init(&ov9734->sd, client, &ov9734_subdev_ops);
+
+	ret = ov9734_power_on(ov9734->dev);
+	if (ret)
+		return ret;
+
 	ret = ov9734_identify_module(ov9734);
 	if (ret) {
 		dev_err(ov9734->dev, "failed to find sensor: %d", ret);
-		return ret;
+		goto probe_error_power_off;
 	}
 
 	mutex_init(&ov9734->mutex);
@@ -945,12 +1024,12 @@ static int ov9734_probe(struct i2c_client *client)
 	}
 
 	/*
-	 * Device is already turned on by i2c-core with ACPI domain PM.
-	 * Enable runtime PM and turn off the device.
+	 * The device is powered on at this point, by ov9734_power_on() and,
+	 * on some platforms, by i2c-core with ACPI domain PM. Enable runtime
+	 * PM and turn off the device once the subdev is registered.
 	 */
 	pm_runtime_set_active(ov9734->dev);
 	pm_runtime_enable(ov9734->dev);
-	pm_runtime_idle(ov9734->dev);
 
 	ret = v4l2_async_register_subdev_sensor(&ov9734->sd);
 	if (ret < 0) {
@@ -959,6 +1038,8 @@ static int ov9734_probe(struct i2c_client *client)
 		goto probe_error_media_entity_cleanup_pm;
 	}
 
+	pm_runtime_idle(ov9734->dev);
+
 	return 0;
 
 probe_error_media_entity_cleanup_pm:
@@ -970,6 +1051,9 @@ static int ov9734_probe(struct i2c_client *client)
 	v4l2_ctrl_handler_free(ov9734->sd.ctrl_handler);
 	mutex_destroy(&ov9734->mutex);
 
+probe_error_power_off:
+	ov9734_power_off(ov9734->dev);
+
 	return ret;
 }
 
@@ -984,6 +1068,7 @@ static struct i2c_driver ov9734_i2c_driver = {
 	.driver = {
 		.name = "ov9734",
 		.acpi_match_table = ov9734_acpi_ids,
+		.pm = pm_ptr(&ov9734_pm_ops),
 	},
 	.probe = ov9734_probe,
 	.remove = ov9734_remove,
-- 
2.53.0