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

[Walt Holman]

On Sat, Jun 21, 2025 at 2:12 PM Mario Limonciello <superm1@xxxxxxxxxx> wrote:
>
>
>
> On 6/21/25 11:07 AM, Walt Holman wrote:
> > On Sat, Jun 21, 2025 at 11:03 AM Walt Holman <waltholman09@xxxxxxxxx> wrote:
> >>
> >> On Sat, Jun 21, 2025 at 10:52 AM Mario Limonciello <superm1@xxxxxxxxxx> 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@xxxxxxx>
> >>>> 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@xxxxxxx>
> >>>>       Cc: Alex Deucher <alexander.deucher@xxxxxxx>
> >>>>       Reviewed-by: Roman Li <roman.li@xxxxxxx>
> >>>>       Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
> >>>>       Signed-off-by: Alex Hung <alex.hung@xxxxxxx>
> >>>>       Tested-by: Daniel Wheeler <daniel.wheeler@xxxxxxx>
> >>>>       Signed-off-by: Alex Deucher <alexander.deucher@xxxxxxx>
> >>>>       (cherry picked from commit 8dbd72cb790058ce52279af38a43c2b302fdd3e5)
> >>>>       Cc: stable@xxxxxxxxxxxxxxx
> >>>>
> >>>>    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

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