Quoting Alexandru Ardelean (2024-11-15 18:07:17)
> From: Naushir Patuck <naush@xxxxxxxxxxxxxxx>
>
> Add a 2-5ms delay when coming out of standby and before reading the
> sensor info register durning probe, as instructed by the datasheet. This
> standby delay is already present when the sensor starts streaming.
>
> During a cold-boot, reading the IMX296_SENSOR_INFO register would often
> return a value of 0x0000, if this delay is not present before.
>
> Fixes: cb33db2b6ccfe ("media: i2c: IMX296 camera sensor driver")
> Tested-by: Alexandru Ardelean <aardelean@xxxxxxxxxxxx>
> Signed-off-by: Naushir Patuck <naush@xxxxxxxxxxxxxxx>
> ---
>
> Changelog v1 -> v2:
> * https://lore.kernel.org/linux-media/20241115142021.574402-1-aardelean@xxxxxxxxxxxx/
> * Technically, this is not a true V2, but rather a new patch
> - But in V1, the attempt was to fix an issue found with the upstream
> IMX296 driver, which was pointed out by Kieran that it was already
> fixed (more elegantly) in the RPi tree.
Thanks,
Reviewed-by: Kieran Bingham <kieran.bingham@xxxxxxxxxxxxxxxx>
> - The standby delay helps during a cold-boot so that the driver can read
> the IMX296_SENSOR_INFO register. If the delay isn't present the value
> read is 0xx0000.
> - Original patch can be found:
> https://github.com/raspberrypi/linux/commit/7713ce38e6a26425ace3a57b3d03ba0125c16f89
> - From the original patch of Naushir Patuck,
> - Added comment
> -------
> During a cold-boot, reading the IMX296_SENSOR_INFO register would often
> return a value of 0x0000, if this delay is not present before.
> -------
> - Added 'Tested-by: Alexandru Ardelean <aardelean@xxxxxxxxxxxx>
> - Added 'Fixes: cb33db2b6ccfe ("media: i2c: IMX296 camera sensor driver")'
>
> drivers/media/i2c/imx296.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/media/i2c/imx296.c b/drivers/media/i2c/imx296.c
> index f942f66fa664..395bfe4fb23d 100644
> --- a/drivers/media/i2c/imx296.c
> +++ b/drivers/media/i2c/imx296.c
> @@ -940,6 +940,8 @@ static int imx296_identify_model(struct imx296 *sensor)
> return ret;
> }
>
> + usleep_range(2000, 5000);
> +
> ret = imx296_read(sensor, IMX296_SENSOR_INFO);
> if (ret < 0) {
> dev_err(sensor->dev, "failed to read sensor information (%d)\n",
> --
> 2.46.1
>
