linux-kernel - Re: [PATCH] drm/panel-edp: Use ktime_get

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Date:   Thu, 17 Nov 2022 13:14:23 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     Drew Davenport <ddavenport@...omium.org>
Cc:     dri-devel@...ts.freedesktop.org, Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Thierry Reding <thierry.reding@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/panel-edp: Use ktime_get_boottime for delays

Hi,

On Fri, Nov 11, 2022 at 12:44 PM Doug Anderson <dianders@...omium.org> wrote:
>
> Hi,
>
> On Thu, Nov 10, 2022 at 1:51 PM Drew Davenport <ddavenport@...omium.org> wrote:
> >
> > ktime_get is based on CLOCK_MONOTONIC which stops on suspend. On
> > suspend, the time that the panel was powerd off is recorded with
> > ktime_get, and on resume this time is compared to the current ktime_get
> > time to determine if the driver should wait for the panel to power down
> > completely before re-enabling it.
> >
> > Because we're using ktime_get, this delay doesn't account for the time
> > that the device is suspended, during which the power down delay may have
> > already elapsed.
> >
> > Change to use ktime_get_boottime throughout, which uses CLOCK_BOOTTIME
> > which does not stop when suspended. This ensures that the resume path
> > will not be delayed if the power off delay has already been met while
> > the device is suspended.
> >
> > Signed-off-by: Drew Davenport <ddavenport@...omium.org>
> >
> > ---
> >
> >  drivers/gpu/drm/panel/panel-edp.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
>
> Nice!
>
> Reviewed-by: Douglas Anderson <dianders@...omium.org>
>
> My plan will be to land this to drm-misc-next early next week (Tuesday
> maybe?) unless someone has any objections.
>
> BTW: any chance you'd be willing to post against two similar drivers:
> panel-simple.c and panel-samsung-atna33xc20.c? They have nearly the
> same code (and, yes, these drivers are purposely copies since there
> was overall consensus that having one giant panel driver to handle all
> possible panels was getting far too confusing)

Breadcrumbs: after discussion, this got vacuumed up into a larger
series and is now at:

https://lore.kernel.org/r/20221117133655.2.Iebd9f79aba0a62015fd2383fe6986c2d6fe12cfd@changeid