RE: [PATCH 1/2] drm/amd/display: Fix the brightness read via aux

["Deucher, Alexander" <Alexander.Deucher@xxxxxxx>]

[AMD Public Use]

> -----Original Message-----
> From: Takashi Iwai <tiwai@xxxxxxx>
> Sent: Saturday, February 6, 2021 7:29 AM
> To: Alex Deucher <alexdeucher@xxxxxxxxx>
> Cc: Deucher, Alexander <Alexander.Deucher@xxxxxxx>; Koenig, Christian
> <Christian.Koenig@xxxxxxx>; Li, Sun peng (Leo) <Sunpeng.Li@xxxxxxx>;
> Wentland, Harry <Harry.Wentland@xxxxxxx>; Maling list - DRI developers
> <dri-devel@xxxxxxxxxxxxxxxxxxxxx>; amd-gfx list <amd-
> gfx@xxxxxxxxxxxxxxxxxxxxx>
> Subject: Re: [PATCH 1/2] drm/amd/display: Fix the brightness read via aux
> 
> On Fri, 05 Feb 2021 17:36:44 +0100,
> Alex Deucher wrote:
> >
> > On Wed, Feb 3, 2021 at 7:42 AM Takashi Iwai <tiwai@xxxxxxx> wrote:
> > >
> > > The current code tries to read the brightness value via
> > > dc_link_get_backlight_level() no matter whether it's controlled via
> > > aux or not, and this results in a bogus value returned.
> > > Fix it to read the current value via
> > > dc_link_get_backlight_level_nits() for the aux.
> > >
> > > BugLink:
> > >
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbu
> > >
> gzilla.opensuse.org%2Fshow_bug.cgi%3Fid%3D1180749&amp;data=04%7C01
> %7
> > >
> Calexander.deucher%40amd.com%7Ce5579cfe56f74b572f1508d8ca9ad0ac%7
> C3d
> > >
> d8961fe4884e608e11a82d994e183d%7C0%7C0%7C637482113562863043%7CU
> nknow
> > >
> n%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1ha
> Wwi
> > >
> LCJXVCI6Mn0%3D%7C1000&amp;sdata=HVtqM2r6oxSWd3XGGQZotO8wrvM
> qCTcwfq1L
> > > 2%2FeCmSE%3D&amp;reserved=0
> > > BugLink:
> > >
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgi
> > > tlab.freedesktop.org%2Fdrm%2Famd%2F-
> %2Fissues%2F1438&amp;data=04%7C0
> > >
> 1%7Calexander.deucher%40amd.com%7Ce5579cfe56f74b572f1508d8ca9ad0
> ac%7
> > >
> C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637482113562863043%
> 7CUnk
> > >
> nown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6I
> k1ha
> > >
> WwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=TdYgwNJ%2FvkuoDLNb9ATFb1P
> yznlp%2F
> > > P8TLuYSR%2BVkNqY%3D&amp;reserved=0
> > > Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
> >
> > This looks fine to me.  FWIW, I have a similar patch set here:
> > https://nam11.safelinks.protection.outlook.com/?url=https:%2F%2Fcgit.f
> >
> reedesktop.org%2F~agd5f%2Flinux%2Flog%2F%3Fh%3Dbacklight_wip&amp;
> data=
> >
> 04%7C01%7Calexander.deucher%40amd.com%7Ce5579cfe56f74b572f1508d8
> ca9ad0
> >
> ac%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637482113562863
> 043%7CU
> >
> nknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI
> 6Ik1ha
> >
> WwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=aoMSY0nvHjrLocUPJtdgckqIH7x
> LUPbwpH0
> > ZjhuuJO8%3D&amp;reserved=0
> 
> I'm fine to scratch mine as long as the issue gets fixed :)
> 
> FWIW, the biggest problem so far was the aux channel backlight didn't work
> as expected, the actual backlight isn't changed by the backlight sysfs write.
> (And the sysfs read gives a bogus value, but it's not the cause of the non-
> working backlight control.)
> 
> Does the aux channel backlight really work with the current code?
> Or is this rather a device-specific issue (e.g. broken BIOS) and we might need
> to come up with a deny list or such?
> 

@Kazlauskas, Nicholas, @Siqueira, Rodrigo

Has there been any progress on the backlight fixes?

Alex
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