linux-kernel - Re: [PATCH v3 2/2] [media] uvcvideo: Remain runtime-suspended at sleeps

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Message-ID: <Pine.LNX.4.44L0.1504171331050.1319-100000@iolanthe.rowland.org>
Date:	Fri, 17 Apr 2015 13:32:50 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Tomeu Vizoso <tomeu.vizoso@...labora.com>
cc:	linux-pm@...r.kernel.org,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	<linux-media@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/2] [media] uvcvideo: Remain runtime-suspended at
 sleeps

On Fri, 17 Apr 2015, Tomeu Vizoso wrote:

> When the system goes to sleep and afterwards resumes, a significant
> amount of time is spent suspending and resuming devices that were
> already runtime-suspended.
> 
> By setting the power.force_direct_complete flag, the PM core will ignore
> the state of descendant devices and the device will be let in
> runtime-suspend.
> 
> Signed-off-by: Tomeu Vizoso <tomeu.vizoso@...labora.com>
> ---
>  drivers/media/usb/uvc/uvc_driver.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
> index 5970dd6..ae75a70 100644
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -1945,6 +1945,8 @@ static int uvc_probe(struct usb_interface *intf,
>  			"supported.\n", ret);
>  	}
>  
> +	intf->dev.parent->power.force_direct_complete = true;

This seems wrong.  The uvc driver is bound to intf, not to intf's
parent.  So it would be okay for the driver to set
intf->dev.power.force_direct_complete, but it's wrong to set
intf->dev.parent->power.force_direct_complete.

Alan Stern

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