linux-kernel - Re: AMDGPU - Regression: Black screen due to commit 16dc8bc27c2aa3c93905d3e885e27f1e3535f09a

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Message-ID: <CAMb39_mpfdjxAH7jp0s7aedi_CsUOOVSR6x=8NG1ehRwWeQ30w@mail.gmail.com>
Date: Mon, 23 Jun 2025 10:35:17 -0500
From: Walt Holman <waltholman09@...il.com>
To: Mario Limonciello <superm1@...nel.org>
Cc: linux-kernel <linux-kernel@...r.kernel.org>, mario.limonciello@....com, 
	alexander.deucher@....com
Subject: Re: AMDGPU - Regression: Black screen due to commit 16dc8bc27c2aa3c93905d3e885e27f1e3535f09a

On Mon, Jun 23, 2025 at 9:51 AM Mario Limonciello <superm1@...nel.org> wrote:
>
> On 6/21/25 2:32 PM, Walt Holman wrote:
> > On Sat, Jun 21, 2025 at 2:12 PM Mario Limonciello <superm1@...nel.org> wrote:
> >>
> >>
> >>
> >> On 6/21/25 11:07 AM, Walt Holman wrote:
> >>> On Sat, Jun 21, 2025 at 11:03 AM Walt Holman <waltholman09@...il.com> wrote:
> >>>>
> >>>> On Sat, Jun 21, 2025 at 10:52 AM Mario Limonciello <superm1@...nel.org> wrote:
> >>>>>
> >>>>>
> >>>>>
> >>>>> On 6/21/25 10:18 AM, Walt Holman wrote:
> >>>>>> Hello,
> >>>>>>
> >>>>>> With the latest drm fixes this week on 6.16-rc2, I am experiencing a
> >>>>>> black screen instead of the sddm greeter and the GPU appears to be
> >>>>>> locked up. I can ssh into the laptop and reboot it, but that's about
> >>>>>> it. I have bisected the commit to commit id:
> >>>>>> 16dc8bc27c2aa3c93905d3e885e27f1e3535f09a and upon reverting the
> >>>>>> commit, the system works as normal. The hardware is an Asus Rog
> >>>>>> Zephyrus G16 with AMD Ryzen AI 9 HX 370 w/ Radeon 890M video. I'm able
> >>>>>> to test patches etc.. if need be.
> >>>>>
> >>>>> Hi there,
> >>>>>
> >>>>> By chance do you have an OLED panel?  If so can you please try the patch
> >>>>> attached to this bug?
> >>>>>
> >>>>> https://gitlab.freedesktop.org/drm/amd/-/issues/4338
> >>>>>
> >>>>> Thanks,
> >>>>>
> >>>>>>
> >>>>>> 16dc8bc27c2aa3c93905d3e885e27f1e3535f09a is the first bad commit
> >>>>>> commit 16dc8bc27c2aa3c93905d3e885e27f1e3535f09a (HEAD)
> >>>>>> Author: Mario Limonciello <mario.limonciello@....com>
> >>>>>> Date:   Thu May 29 09:46:32 2025 -0500
> >>>>>>
> >>>>>>        drm/amd/display: Export full brightness range to userspace
> >>>>>>
> >>>>>>        [WHY]
> >>>>>>        Userspace currently is offered a range from 0-0xFF but the PWM is
> >>>>>>        programmed from 0-0xFFFF.  This can be limiting to some software
> >>>>>>        that wants to apply greater granularity.
> >>>>>>
> >>>>>>        [HOW]
> >>>>>>        Convert internally to firmware values only when mapping custom
> >>>>>>        brightness curves because these are in 0-0xFF range. Advertise full
> >>>>>>        PWM range to userspace.
> >>>>>>
> >>>>>>        Cc: Mario Limonciello <mario.limonciello@....com>
> >>>>>>        Cc: Alex Deucher <alexander.deucher@....com>
> >>>>>>        Reviewed-by: Roman Li <roman.li@....com>
> >>>>>>        Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> >>>>>>        Signed-off-by: Alex Hung <alex.hung@....com>
> >>>>>>        Tested-by: Daniel Wheeler <daniel.wheeler@....com>
> >>>>>>        Signed-off-by: Alex Deucher <alexander.deucher@....com>
> >>>>>>        (cherry picked from commit 8dbd72cb790058ce52279af38a43c2b302fdd3e5)
> >>>>>>        Cc: stable@...r.kernel.org
> >>>>>>
> >>>>>>     drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 41
> >>>>>> +++++++++++++++++++++++++++--------------
> >>>>>>     1 file changed, 27 insertions(+), 14 deletions(-)
> >>>>>>
> >>>>>
> >>>>
> >>>> Yes, I do have an OLED panel and that patch does make it visible
> >>>> again. It is still very dark, but visible.
> >>>>
> >>>> -Walt
> >>>
> >>> Upon rebooting again, the display was much brighter and is fine. Just
> >>> the first boot after that was dark.
> >>>
> >>> -Walt
> >>
> >> Thanks, this makes sense.  I suspect that because 0 means "off" for your
> >> panel that the patch you bisected to exposed running at 0 (or near
> >> enough to 0) that it caused this behavior.
> >>
> >> That patch you tested will be upstreamed in a future promotion, and I
> >> think we can take it in a -fixes PR later in the 6.16 fixes cycle.
> >>
> >> But there is one more thing I would like to confirm - on your system can
> >> you run with drm.debug=0x106 on the kernel command line and share me the
> >> output from this debug print?
> >>
> >> https://github.com/torvalds/linux/blob/v6.16-rc2/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c#L4933
> >>
> >>
> >>
> > Hopefully, this is what you need. I grepped dmesg for drm and threw it
> > into this file attached. Let me know if you need anything else.
> >
> > -Walt
>
> Thanks I see another problem.  Can you add this patch?
>
> https://lore.kernel.org/amd-gfx/20250623144821.745908-1-mario.limonciello@amd.com/T/#u
>
> Thanks,

Got it added. Can't say that I notice a big difference, however, the
login screen may have been a tad brighter. But it's obviously more
correct now. Thanks,

-Walt