linux-kernel - Re: [PATCH v4 13/15] media: mt9m114: Drop start-, stop-streaming sequence from initialize

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Message-ID: <20251228172036.GP4094@pendragon.ideasonboard.com>
Date: Sun, 28 Dec 2025 19:20:36 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Hans de Goede <johannes.goede@....qualcomm.com>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 13/15] media: mt9m114: Drop start-, stop-streaming
 sequence from initialize

Hi Hans,

Thank you for the patch.

On Wed, Dec 24, 2025 at 01:31:22PM +0100, Hans de Goede wrote:
> Drop the start-, stop-streaming sequence from initialize.
> 
> When streaming is started with a runtime-suspended sensor,
> mt9m114_start_streaming() will runtime-resume the sensor which calls
> mt9m114_initialize() immediately followed by calling
> mt9m114_set_state(ENTER_CONFIG_CHANGE).
> 
> This results in the following state changes in quick succession:
> 
> mt9m114_set_state(ENTER_CONFIG_CHANGE) -> transitions to STREAMING
> mt9m114_set_state(ENTER_SUSPEND)       -> transitions to SUSPENDED
> mt9m114_set_state(ENTER_CONFIG_CHANGE) -> transitions to STREAMING
> 
> these quick state changes confuses the CSI receiver on atomisp devices
> causing streaming to not work.
> 
> Drop the state changes from mt9m114_initialize() and move
> the mt9m114_initialize() call to mt9m114_start_streaming()
> so that only a single mt9m114_set_state(ENTER_CONFIG_CHANGE) call
> is made when streaming is started with a runtime-suspend sensor.
> 
> Signed-off-by: Hans de Goede <johannes.goede@....qualcomm.com>
> ---
> Changes in v4:
> - Move the mt9m114_initialize() call to mt9m114_start_streaming()
>   and drop the config_change_pending flag
> ---
>  drivers/media/i2c/mt9m114.c | 33 +++++++--------------------------
>  1 file changed, 7 insertions(+), 26 deletions(-)
> 
> diff --git a/drivers/media/i2c/mt9m114.c b/drivers/media/i2c/mt9m114.c
> index 447a5eb34a6137a8e87bd119401571b5592fc77d..41e98f719a23045293ee47d8980675510a142afa 100644
> --- a/drivers/media/i2c/mt9m114.c
> +++ b/drivers/media/i2c/mt9m114.c
> @@ -789,14 +789,6 @@ static int mt9m114_initialize(struct mt9m114 *sensor)
>  	if (ret < 0)
>  		return ret;
>  
> -	ret = mt9m114_set_state(sensor, MT9M114_SYS_STATE_ENTER_CONFIG_CHANGE);
> -	if (ret < 0)
> -		return ret;
> -
> -	ret = mt9m114_set_state(sensor, MT9M114_SYS_STATE_ENTER_SUSPEND);
> -	if (ret < 0)
> -		return ret;
> -
>  	return 0;
>  }
>  
> @@ -967,6 +959,10 @@ static int mt9m114_start_streaming(struct mt9m114 *sensor,
>  	if (ret)
>  		return ret;
>  
> +	ret = mt9m114_initialize(sensor);
> +	if (ret)
> +		goto error;
> +
>  	ret = mt9m114_configure_ifp(sensor, ifp_state);
>  	if (ret)
>  		goto error;
> @@ -2318,19 +2314,8 @@ static int __maybe_unused mt9m114_runtime_resume(struct device *dev)
>  {
>  	struct v4l2_subdev *sd = dev_get_drvdata(dev);
>  	struct mt9m114 *sensor = ifp_to_mt9m114(sd);
> -	int ret;
>  
> -	ret = mt9m114_power_on(sensor);
> -	if (ret)
> -		return ret;
> -
> -	ret = mt9m114_initialize(sensor);
> -	if (ret) {
> -		mt9m114_power_off(sensor);
> -		return ret;
> -	}
> -
> -	return 0;
> +	return mt9m114_power_on(sensor);
>  }
>  
>  static int __maybe_unused mt9m114_runtime_suspend(struct device *dev)
> @@ -2562,8 +2547,8 @@ static int mt9m114_probe(struct i2c_client *client)
>  	/*
>  	 * Identify the sensor. The driver supports runtime PM, but needs to
>  	 * work when runtime PM is disabled in the kernel. To that end, power
> -	 * the sensor on manually here, and initialize it after identification
> -	 * to reach the same state as if resumed through runtime PM.
> +	 * the sensor on manually here and identify it to reach the same state

s/and identify it //

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

> +	 * as if resumed through runtime PM.
>  	 */
>  	ret = mt9m114_power_on(sensor);
>  	if (ret < 0) {
> @@ -2575,10 +2560,6 @@ static int mt9m114_probe(struct i2c_client *client)
>  	if (ret < 0)
>  		goto error_power_off;
>  
> -	ret = mt9m114_initialize(sensor);
> -	if (ret < 0)
> -		goto error_power_off;
> -
>  	/*
>  	 * Enable runtime PM with autosuspend. As the device has been powered
>  	 * manually, mark it as active, and increase the usage count without

-- 
Regards,

Laurent Pinchart