linux-kernel - Re: [REGRESSION] Black screen on HDMI power-cycle after commit 3471b9a31ce3 (7900XTX + LG C3)

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Message-ID: <CABXGCsO5muCnzd+r5jtN-0sevzHxv_5aO7uLJZz7cwdfmK8bQA@mail.gmail.com>
Date: Thu, 11 Dec 2025 11:42:09 +0500
From: Mikhail Gavrilov <mikhail.v.gavrilov@...il.com>
To: "Pillai, Aurabindo" <Aurabindo.Pillai@....com>
Cc: "Deucher, Alexander" <Alexander.Deucher@....com>, amd-gfx list <amd-gfx@...ts.freedesktop.org>, 
	Linux List Kernel Mailing <linux-kernel@...r.kernel.org>, 
	"Vojvodic, Relja (Reggie)" <Relja.Vojvodic@....com>, "Liu, Wenjing" <Wenjing.Liu@....com>
Subject: Re: [REGRESSION] Black screen on HDMI power-cycle after commit
 3471b9a31ce3 (7900XTX + LG C3)

On Wed, Dec 10, 2025 at 1:49 PM Mikhail Gavrilov
<mikhail.v.gavrilov@...il.com> wrote:
> I have performed the partial revert tests as requested. Here are the results:
>
> Reverting ONLY link_detection.c (read hunk): The issue persists. I
> still get "No Signal" after replugging the HDMI cable. (Log attached:
> dmesg-6.18.0-cb015814f8b6-hunk-1-read.zip)
>
> Reverting ONLY link_ddc.c (write hunk): The issue is FIXED. The
> display works correctly and wakes up immediately after replugging the
> cable. (Log attached: dmesg-6.18.0-cb015814f8b6-hunk-2-write.zip)
>
> Conclusion: It seems the regression is specifically caused by the
> changes in drivers/gpu/drm/amd/display/dc/link/protocols/link_ddc.c
> (the write_scdc_data function). The change in link_detection.c appears
> to be unrelated to the failure on my setup.
>
> --
> Best Regards,
> Mike Gavrilov.

Hi Aurabindo,

Important addition:

1. Primary Regression (Power Cycle) - FIXED
I am happy to confirm that your patch "drm/amd/display: Improve HDMI
info retrieval" fully resolves the main regression (TV failing to wake
up after being turned off overnight). This is a critical fix for daily
usage.

2. Physical Hotplug Instability (Pre-existing Issue)
I have also confirmed that physical HDMI replugging remains
unreliable, and this appears to be a separate, pre-existing issue (it
was unstable even before commit 3471b9a31ce3).
Even with your patch applied, the physical hotplug is not 100%
reliable. The image was restored twice, but on the third attempt, I
received the "No signal" message.
The attached log
(dmesg-6.18.0-0048fbb4011e-with-Improve-HDMI-info-retrieval.zip) was
captured during a failed hotplug attempt (with your patch applied on
top of 0048fbb4011e).
Crucially, the log shows a much deeper issue during the failed
hotplug: a device loss, possibly related to SMU (System Management
Unit) power handling:

[ 600.267548] amdgpu 0000:03:00.0: amdgpu: device lost from bus!
[ 600.267568] amdgpu 0000:03:00.0: amdgpu: SMU: response:0xFFFFFFFF
for index:36 param:0x00000001 message:SetWorkloadMask?
[ 600.267574] amdgpu 0000:03:00.0: amdgpu: Failed to set workload mask
0x00000001
[ 600.267586] amdgpu 0000:03:00.0: amdgpu: (-121) failed to disable
fullscreen 3D power profile mode

This persistent SMU/device loss problem seems to be the cause of the
general hotplug unreliability and requires a separate fix.
Please let me know if you need any other logs, or if I should file a
new bug report specifically for the "amdgpu: device lost from bus!"
issue.

-- 
Best Regards,
Mike Gavrilov.

Download attachment "dmesg-6.18.0-0048fbb4011e-with-Improve-HDMI-info-retrieval.zip" of type "application/zip" (71205 bytes)