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

[Mario Limonciello <superm1@kernel.org>]

On 6/21/25 2:32 PM, Walt Holman wrote:
> On Sat, Jun 21, 2025 at 2:12 PM Mario Limonciello <superm1@kernel.org> wrote:
>>
>>
>>
>> On 6/21/25 11:07 AM, Walt Holman wrote:
>>> On Sat, Jun 21, 2025 at 11:03 AM Walt Holman <waltholman09@gmail.com> wrote:
>>>>
>>>> On Sat, Jun 21, 2025 at 10:52 AM Mario Limonciello <superm1@kernel.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@amd.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@amd.com>
>>>>>>        Cc: Alex Deucher <alexander.deucher@amd.com>
>>>>>>        Reviewed-by: Roman Li <roman.li@amd.com>
>>>>>>        Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
>>>>>>        Signed-off-by: Alex Hung <alex.hung@amd.com>
>>>>>>        Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
>>>>>>        Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
>>>>>>        (cherry picked from commit 8dbd72cb790058ce52279af38a43c2b302fdd3e5)
>>>>>>        Cc: stable@vger.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,