Re: [linux-pm] [PATCH/RESEND] soc-camera: add runtime pm support for subdevices

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Monday 08 February 2010, Guennadi Liakhovetski wrote:
> To save power soc-camera powers subdevices down, when they are not in use, 
> if this is supported by the platform. However, the V4L standard dictates, 
> that video nodes shall preserve configuration between uses. This requires 
> runtime power management, which is implemented by this patch. It allows 
> subdevice drivers to specify their runtime power-management methods, by 
> assigning a type to the video device.

You need a support for that at the bus type/device type/device class level,
because the core doesn't execute the driver callbacks directly.

Rafael

> 
> Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
> ---
> 
> I've posted this patch to linux-media earlier, but I'd also like to get 
> comments on linux-pm, sorry to linux-media falks for a duplicate. To 
> explain a bit - soc_camera.c is a management module, that binds video 
> interfaces on SoCs and sensor drivers. The calls, that I am adding to 
> soc_camera.c shall save and restore sensor registers before they are 
> powered down and after they are powered up.
> 
> diff --git a/drivers/media/video/soc_camera.c b/drivers/media/video/soc_camera.c
> index 6b3fbcc..53201f3 100644
> --- a/drivers/media/video/soc_camera.c
> +++ b/drivers/media/video/soc_camera.c
> @@ -24,6 +24,7 @@
>  #include <linux/mutex.h>
>  #include <linux/module.h>
>  #include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
>  #include <linux/vmalloc.h>
>  
>  #include <media/soc_camera.h>
> @@ -387,6 +388,11 @@ static int soc_camera_open(struct file *file)
>  			goto eiciadd;
>  		}
>  
> +		pm_runtime_enable(&icd->vdev->dev);
> +		ret = pm_runtime_resume(&icd->vdev->dev);
> +		if (ret < 0 && ret != -ENOSYS)
> +			goto eresume;
> +
>  		/*
>  		 * Try to configure with default parameters. Notice: this is the
>  		 * very first open, so, we cannot race against other calls,
> @@ -408,10 +414,12 @@ static int soc_camera_open(struct file *file)
>  	return 0;
>  
>  	/*
> -	 * First five errors are entered with the .video_lock held
> +	 * First four errors are entered with the .video_lock held
>  	 * and use_count == 1
>  	 */
>  esfmt:
> +	pm_runtime_disable(&icd->vdev->dev);
> +eresume:
>  	ici->ops->remove(icd);
>  eiciadd:
>  	if (icl->power)
> @@ -436,7 +444,11 @@ static int soc_camera_close(struct file *file)
>  	if (!icd->use_count) {
>  		struct soc_camera_link *icl = to_soc_camera_link(icd);
>  
> +		pm_runtime_suspend(&icd->vdev->dev);
> +		pm_runtime_disable(&icd->vdev->dev);
> +
>  		ici->ops->remove(icd);
> +
>  		if (icl->power)
>  			icl->power(icd->pdev, 0);
>  	}
> @@ -1294,6 +1306,7 @@ static int video_dev_create(struct soc_camera_device *icd)
>   */
>  static int soc_camera_video_start(struct soc_camera_device *icd)
>  {
> +	struct device_type *type = icd->vdev->dev.type;
>  	int ret;
>  
>  	if (!icd->dev.parent)
> @@ -1310,6 +1323,9 @@ static int soc_camera_video_start(struct soc_camera_device *icd)
>  		return ret;
>  	}
>  
> +	/* Restore device type, possibly set by the subdevice driver */
> +	icd->vdev->dev.type = type;
> +
>  	return 0;
>  }
>  
> diff --git a/include/media/soc_camera.h b/include/media/soc_camera.h
> index dcc5b86..58b39a9 100644
> --- a/include/media/soc_camera.h
> +++ b/include/media/soc_camera.h
> @@ -282,4 +282,12 @@ static inline void soc_camera_limit_side(unsigned int *start,
>  extern unsigned long soc_camera_apply_sensor_flags(struct soc_camera_link *icl,
>  						   unsigned long flags);
>  
> +/* This is only temporary here - until v4l2-subdev begins to link to video_device */
> +#include <linux/i2c.h>
> +static inline struct video_device *soc_camera_i2c_to_vdev(struct i2c_client *client)
> +{
> +	struct soc_camera_device *icd = client->dev.platform_data;
> +	return icd->vdev;
> +}
> +
>  #endif
> _______________________________________________