Re: [PATCH] media: ov2740: Ensure proper reset sequence on probe()

[Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com>]

On Mon, May 06, 2024 at 03:24:38PM +0200, Hans de Goede wrote:
> Before this commit on probe() the driver would do:
> 
> reset=1                // from probe() calling gpiod_get(GPIOD_OUT_HIGH)
> reset=0                // from resume()
> msleep(20)             // from resume()
> 
> So if reset was 0 before getting the GPIO the reset line would only be
> driven high for a very short time and sometimes there would be errors
> reading the id register afterwards.
> 
> Add a msleep(20) after getting the reset line to ensure the sensor is
> properly reset:
> 
> reset=1                // from probe() calling gpiod_get(GPIOD_OUT_HIGH)
> msleep(20)             // from probe()
> reset=0                // from resume()
> msleep(20)             // from resume()
> 
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>

Tested-by: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com>

This fixes this issue:

[    7.742633] ov2740 i2c-INT3474:01: chip id mismatch: 2740 != 0
[    7.742638] ov2740 i2c-INT3474:01: error -ENXIO: failed to find sensor

for me as well.

Thanks!
Stanislaw

> ---
>  drivers/media/i2c/ov2740.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/media/i2c/ov2740.c b/drivers/media/i2c/ov2740.c
> index 57906df7be4e..c48dbcde9877 100644
> --- a/drivers/media/i2c/ov2740.c
> +++ b/drivers/media/i2c/ov2740.c
> @@ -1333,9 +1333,16 @@ static int ov2740_probe(struct i2c_client *client)
>  		return dev_err_probe(dev, ret, "failed to check HW configuration\n");
>  
>  	ov2740->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
> -	if (IS_ERR(ov2740->reset_gpio))
> +	if (IS_ERR(ov2740->reset_gpio)) {
>  		return dev_err_probe(dev, PTR_ERR(ov2740->reset_gpio),
>  				     "failed to get reset GPIO\n");
> +	} else if (ov2740->reset_gpio) {
> +		/*
> +		 * Ensure reset is asserted for at least 20 ms before
> +		 * ov2740_resume() deasserts it.
> +		 */
> +		msleep(20);
> +	}
>  
>  	ov2740->clk = devm_clk_get_optional(dev, "clk");
>  	if (IS_ERR(ov2740->clk))
> -- 
> 2.44.0
>