Re: [PATCH] mei: vsc: Don't stop/restart mei device during system suspend/resume

[Sakari Ailus]

Hi Wentong,

Thanks for the patch. I thought something like this would indeed have been
possible.

On Thu, May 16, 2024 at 09:54:00AM +0800, Wentong Wu wrote:
> The dynamically created mei client device (mei csi) is used as one V4L2
> sub device of the whole video pipeline, and the V4L2 connection graph is
> built by software node. The mei_stop() and mei_restart() will delete the
> old mei csi client device and create a new mei client device, which will
> cause the software node information saved in old mei csi device lost and
> the whole video pipeline will be broken.
> 
> Removing mei_stop()/mei_restart() during system suspend/resume can fix
> the issue above and won't impact hardware actual power saving logic.
> 
> Fixes: 386a766c4169 ("mei: Add MEI hardware support for IVSC device")

I think this should be instead:

Fixes: f6085a96c973 ("mei: vsc: Unregister interrupt handler for system suspend")

As this fix depends on the previous not-quite-as-good fix.

Reviewed-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
Tested-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>

> Cc: stable@xxxxxxxxxxxxxxx # for 6.8+
> Reported-by: Hao Yao <hao.yao@xxxxxxxxx>
> Signed-off-by: Wentong Wu <wentong.wu@xxxxxxxxx>
> Tested-by: Jason Chen <jason.z.chen@xxxxxxxxx>
> ---
>  drivers/misc/mei/platform-vsc.c | 39 +++++++++++++--------------------
>  1 file changed, 15 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/misc/mei/platform-vsc.c b/drivers/misc/mei/platform-vsc.c
> index b543e6b9f3cf..1ec65d87488a 100644
> --- a/drivers/misc/mei/platform-vsc.c
> +++ b/drivers/misc/mei/platform-vsc.c
> @@ -399,41 +399,32 @@ static void mei_vsc_remove(struct platform_device *pdev)
>  
>  static int mei_vsc_suspend(struct device *dev)
>  {
> -	struct mei_device *mei_dev = dev_get_drvdata(dev);
> -	struct mei_vsc_hw *hw = mei_dev_to_vsc_hw(mei_dev);
> +	struct mei_device *mei_dev;
> +	int ret = 0;
>  
> -	mei_stop(mei_dev);
> +	mei_dev = dev_get_drvdata(dev);
> +	if (!mei_dev)
> +		return -ENODEV;
>  
> -	mei_disable_interrupts(mei_dev);
> +	mutex_lock(&mei_dev->device_lock);
>  
> -	vsc_tp_free_irq(hw->tp);
> +	if (!mei_write_is_idle(mei_dev))
> +		ret = -EAGAIN;
>  
> -	return 0;
> +	mutex_unlock(&mei_dev->device_lock);
> +
> +	return ret;
>  }
>  
>  static int mei_vsc_resume(struct device *dev)
>  {
> -	struct mei_device *mei_dev = dev_get_drvdata(dev);
> -	struct mei_vsc_hw *hw = mei_dev_to_vsc_hw(mei_dev);
> -	int ret;
> -
> -	ret = vsc_tp_request_irq(hw->tp);
> -	if (ret)
> -		return ret;
> -
> -	ret = mei_restart(mei_dev);
> -	if (ret)
> -		goto err_free;
> +	struct mei_device *mei_dev;
>  
> -	/* start timer if stopped in suspend */
> -	schedule_delayed_work(&mei_dev->timer_work, HZ);
> +	mei_dev = dev_get_drvdata(dev);
> +	if (!mei_dev)
> +		return -ENODEV;
>  
>  	return 0;
> -
> -err_free:
> -	vsc_tp_free_irq(hw->tp);
> -
> -	return ret;
>  }
>  
>  static DEFINE_SIMPLE_DEV_PM_OPS(mei_vsc_pm_ops, mei_vsc_suspend, mei_vsc_resume);

-- 
Kind regards,

Sakari Ailus