linux-kernel - Re: [RFC PATCH] drm/edid: Make 144 Hz not preferred on Sharp LQ140M1JW46

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Message-ID: <8735dtq1vq.fsf@intel.com>
Date:   Thu, 18 Aug 2022 13:31:21 +0300
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Doug Anderson <dianders@...omium.org>,
        Maxime Ripard <maxime@...no.tech>
Cc:     Sankeerth Billakanti <quic_sbillaka@...cinc.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        freedreno <freedreno@...ts.freedesktop.org>
Subject: Re: [RFC PATCH] drm/edid: Make 144 Hz not preferred on Sharp
 LQ140M1JW46

On Wed, 17 Aug 2022, Doug Anderson <dianders@...omium.org> wrote:
> Hi,
>
> On Sun, Aug 14, 2022 at 11:46 PM Maxime Ripard <maxime@...no.tech> wrote:
>>
>> On Fri, Jul 29, 2022 at 12:57:40PM -0700, Doug Anderson wrote:
>> > Hi,
>> >
>> > On Fri, Jul 29, 2022 at 9:41 AM Maxime Ripard <maxime@...no.tech> wrote:
>> > > You raise some good points, but most of the discussion around that patch
>> > > were mostly around performances, power consumption and so on.
>> > >
>> > > This is very much a policy decision, and if there is some panel where
>> > > the EDID reports 60Hz but is broken, then that panel should be the
>> > > exception to the policy
>> > >
>> > > But doing it for a single panel is just odd
>> >
>> > OK, fair enough. I'll abandon this patch at least as far as mainline
>> > is concerned, then.
>>
>> That wasn't really my point though :)
>>
>> If you think that this change is needed, then we should totally discuss
>> it and I'm not opposed to it.
>>
>> What I don't really like about this patch is that it's about a single
>> panel: if we're doing it we should do it for all the panels.
>>
>> Where we do it can also be discussed, but we should remain consistent
>> there.
>
> I was never massively confident about it, which is why I added the
> "RFC" tag to begin with. ;-) In general I suspect that either change
> will make people upset. In other words, if we programmatically always
> try to put the "high refresh rate" first for all displays then people
> will be upset and if we programmatically always try to put the "60 Hz
> rate" first then people will be upset. Unless someone wants to stand
> up and say that one side or the other is wrong, I think we're going to
> simply leave this up to the whim of individual panels. Someone could
> stand up and demand that it go one way or the other, but I certainly
> don't have that clout.
>
> The spec, as far as I can tell, says that it's up to the panel vendor
> to use whatever means they want to decide on the "preferred" refresh
> rate. Thus, as far as the spec is concerned this decision is made on
> an individual panel basis. ;-) This was really the justification for
> why my patch was just on one panel.
>
> In any case, as I said I'm OK w/ dropping this. We'll find other ways
> to work around the issue.

FWIW, if the EDID reported preferred mode works, I also think that's
what we should prefer.

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Graphics Center