linux-kernel - Re: [PATCH] pm: sleep: do not set is_prepared when no_pm

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Message-ID: <2024090347-latter-collide-772a@gregkh>
Date: Tue, 3 Sep 2024 12:23:55 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: David Wang <00107082@....com>
Cc: rafael@...nel.org, pavel@....cz, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pm: sleep: do not set is_prepared when no_pm_callbacks
 is set

On Mon, Sep 02, 2024 at 08:59:33PM +0800, David Wang wrote:
> When resume, a parent device with no pm callbacks
> would have "is_prepared" and "direct_complete" bit
> set, and skip the "fib" chance to unset "is_prepared"
> in device_resume because of the direct_complete bit.
> This will trigger a kernel warning when resume its child
> For example, when suspend system with an USB webcam
> opened, following warning would show up during resume:
> 
>  >usb 3-1.1: reset high-speed USB device number 4 using xhci_hcd
>  >..
>  >ep_81: PM: parent 3-1.1:1.1 should not be sleeping
> 
> The device parenting relationships are:
> [usb 3-1.1] << [uvcvideo 3-1.1:1.1] << [ep_81].
> When resume, since the virtual [uvcvideo 3-1.1:1.1] device
> has no pm callbacks, it would not clear "is_prepared"
> once set.  Then, when resume [ep_81], pm module would
> yield a warn seeing [ep_81]'s parent [uvcvideo 3-1.1:1.1]
> having "is_prepared".
> 
> Do not set "is_prepared" for virtual devices having
> no pm callbacks can clear those kernel warnings.
> 
> Signed-off-by: David Wang <00107082@....com>
> ---
>  drivers/base/power/main.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)

What commit id does this fix?

thanks,

greg k-h