Re: drm/amd/display: Pass pwrseq inst for backlight and ABM

[Christoph Biedl <linux-kernel.bfrz@manchmal.in-ulm.de>]

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Alex Deucher wrote... [ back in January ]

> Please cherry pick upstream commit b17ef04bf3a4 ("drm/amd/display:
> Pass pwrseq inst for backlight and ABM") to stable kernel 6.6.x and
> newer.
>
> This fixes broken backlight adjustment on some AMD platforms with eDP panels.

Hello,

tl;dr: Was it possible to have this in 6.1.y?

after a lenghty bisect session it seems[1] this commit b17ef04bf3a4
("drm/amd/display: Pass pwrseq inst for backlight and ABM") indeed
fixes an issue with a HP mt645[2]: Without it, the backlight stays at
full brightness all the time, writing various values to the usual sysfs
place has no effect.

That commit was backported to 6.6.y (as 71be0f674070) but not to 6.1.y -
which is the series where I'd like to see that issue fixed. However, is
does not apply, lot of failed hunks and missing files. So I was
wondering whether it had been skipped deliberately because a backport
was deemed impossible - or whether it might be doable with some
more-than-usual effort. In the latter case, I might be willing to do the
task, but quite frankly, lacking any understanding of what the code
does, I'd only try to resolve the conflicts and check whether things
work.

So I'd be glad if you could give me some insight here: Would it be worth
the efforts trying to bring this to 6.1.y?

Kind regards,

    Christoph

[1] Being a bit blurry here for a reason: I bisected on the 6.6.y
branch, had to skip several commits as X would no longer start, and
ended up with

| There are only 'skip'ped commits left to test.
| The first bad commit could be any of:
| 18562b1691e2280858f291d00678468cf70bda5a
| a5ba95c226b5c25cd5c8b9df29a1953c85a1531e
| 71be0f674070a5ad54a1c4fb112bb2923b28ea50
| We cannot bisect more!

where the last one looks like the most obvious candidate, even more
after reading this thread, and re-testing with that one on top of the
last usable commit indeed gave a positive result.

[2]
From lspci:

| e5:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Rembrandt [Radeon 680M] [1002:1681] (rev 0d)

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