Re: [PATCH v1] media: ov08x40: Avoid sensor probing in D0 state

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Hi Jason,

On Fri, Jan 05, 2024 at 06:20:08PM +0800, Chen, Jason Z wrote:
> From: Jason Chen <jason.z.chen@xxxxxxxxx>
> 
> When the system enters the D0 state and attempt to probe the device,
> another component, such as LED, will also be pulled high due to the
> hardware design. It's advisable to keep the device being probed in
> a different D state.
> 
> Signed-off-by: Jason Chen <jason.z.chen@xxxxxxxxx>
> ---
>  drivers/media/i2c/ov08x40.c | 18 ++++++++++++------
>  1 file changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/media/i2c/ov08x40.c b/drivers/media/i2c/ov08x40.c
> index 8f24be08c7b..f46cf0eb6c1 100644
> --- a/drivers/media/i2c/ov08x40.c
> +++ b/drivers/media/i2c/ov08x40.c
> @@ -3226,6 +3226,7 @@ static int ov08x40_probe(struct i2c_client *client)
>  {
>  	struct ov08x40 *ov08x;
>  	int ret;
> +	bool full_power;
>  
>  	/* Check HW config */
>  	ret = ov08x40_check_hwcfg(&client->dev);
> @@ -3241,11 +3242,14 @@ static int ov08x40_probe(struct i2c_client *client)
>  	/* Initialize subdev */
>  	v4l2_i2c_subdev_init(&ov08x->sd, client, &ov08x40_subdev_ops);
>  
> -	/* Check module identity */
> -	ret = ov08x40_identify_module(ov08x);
> -	if (ret) {
> -		dev_err(&client->dev, "failed to find sensor: %d\n", ret);
> -		return ret;
> +	full_power = acpi_dev_state_d0(&client->dev);
> +	if (full_power) {
> +		/* Check module identity */
> +		ret = ov08x40_identify_module(ov08x);

This way the sensor identification will be missed if the device wasn't
powered on im probe. See e.g. commit d1d2ed5925c370ac09fa6efd39f5f569f562e5b7
for an example.

> +		if (ret) {
> +			dev_err(&client->dev, "failed to find sensor: %d\n", ret);
> +			return ret;
> +		}
>  	}
>  
>  	/* Set default mode to max resolution */
> @@ -3277,7 +3281,8 @@ static int ov08x40_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.
>  	 */

Please remove this comment, too.

> -	pm_runtime_set_active(&client->dev);
> +	if (full_power)
> +		pm_runtime_set_active(&client->dev);
>  	pm_runtime_enable(&client->dev);
>  	pm_runtime_idle(&client->dev);
>  
> @@ -3321,6 +3326,7 @@ static struct i2c_driver ov08x40_i2c_driver = {
>  	},
>  	.probe = ov08x40_probe,
>  	.remove = ov08x40_remove,
> +	.flags = I2C_DRV_ACPI_WAIVE_D0_PROBE,
>  };
>  
>  module_i2c_driver(ov08x40_i2c_driver);

-- 
Regards,

Sakari Ailus




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