[PATCH v4 2/2] media: i2c: ov02c10: Correct power-on sequence and timing

[Saikiran <bjsaikiran@gmail.com>]

The previous power-on sequence did not strictly follow the hardware timing
requirements (T1), potentially leading to initialization failures on some
platforms.

Update the sequence to match the datasheet and maintainer recommendations:
1. Assert XSHUTDOWN (reset) for 5ms (T1 >= 5ms) before enabling power
   resources.
2. Enable clock and regulators in the standard order.
3. De-assert XSHUTDOWN.
4. Wait 5ms (T2 >= 5ms) for sensor boot before I2C access (using a wider
   range for timer coalescing).

This ensures the sensor enters a clean state during cold boot.

Tested-on: Lenovo Yoga Slim 7x (Snapdragon X Elite)
Fixes: 44f8901 ("media: i2c: add OmniVision OV02C10 sensor driver")
Cc: stable@vger.kernel.org
Signed-off-by: Saikiran <bjsaikiran@gmail.com>
---
 drivers/media/i2c/ov02c10.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/media/i2c/ov02c10.c b/drivers/media/i2c/ov02c10.c
index fa7cc48b769a..3bfbd0deb126 100644
--- a/drivers/media/i2c/ov02c10.c
+++ b/drivers/media/i2c/ov02c10.c
@@ -676,6 +676,12 @@ static int ov02c10_power_on(struct device *dev)
 	struct ov02c10 *ov02c10 = to_ov02c10(sd);
 	int ret;
 
+	/* Assert reset for 5ms to ensure sensor is in reset state */
+	if (ov02c10->reset) {
+		gpiod_set_value_cansleep(ov02c10->reset, 1);
+		usleep_range(5000, 6000);
+	}
+
 	ret = clk_prepare_enable(ov02c10->img_clk);
 	if (ret < 0) {
 		dev_err(dev, "failed to enable imaging clock: %d", ret);
@@ -691,10 +697,8 @@ static int ov02c10_power_on(struct device *dev)
 	}
 
 	if (ov02c10->reset) {
-		/* Assert reset for at least 2ms on back to back off-on */
-		usleep_range(2000, 2200);
 		gpiod_set_value_cansleep(ov02c10->reset, 0);
-		usleep_range(5000, 5100);
+		usleep_range(5000, 5500);
 	}
 
 	return 0;
-- 
2.51.0