Re: [PATCH v4 0/4] HDMI 2.1 VRR and ALLM support

[Adolfo <adolfotregosa@gmail.com>]

I patched kernel 7.3-rc1, and I have KDE's Adaptive Sync property set to 
Automatic (Always makes the display gamma flicker). VRR itself is only 
engaged when entering a game.

My display (an LG C1 connected through an Onkyo RZ70 AVR) shows "fixed" 
when VRR is not active. While this seems logical, it causes the display 
to go blank every time I enter or exit a game, or, even worse, when I 
alt-tab while in a game.

In my case, I can have periods of up to 10 seconds with no image while 
the devices in the HDMI chain disagree with each other, and sometimes I 
lose the image completely.

A kernel parameter to force VRR to always be enabled should be 
available. This would prevent these signal-switching problems, and it is 
how "FreeSync" actually works and also with the unofficial kernel 
patches for AMD HDMI 2.1 + VRR on kernel 7.2.

There is also some evidence that keeping VRR active can avoid the 
mode-switch behavior seen on some TVs when VRR is enabled or disabled.

On 14/08/2026 17:43, Fangzhi Zuo wrote:
> This series adds HDMI 2.1 gaming support to amdgpu: Variable Refresh Rate
> (VRR) derived from the HDMI Forum VSDB (HF-VSDB), and Auto Low-Latency
> Mode (ALLM). It builds on a drm/edid patch that parses the HF-VSDB gaming
> capabilities into struct drm_hdmi_info.
>
>    - Patch 1 reports FreeSync from the AMD VSDB (existing mechanism).
>    - Patch 2 (drm/edid) parses the HF-VSDB VRR range and ALLM bit.
>    - Patch 3 enables VRR from the HF-VSDB when the AMD VSDB has no range.
>    - Patch 4 signals ALLM_Mode in the HF-VSIF when Gaming-VRR is active.
>
> v1: https://lore.kernel.org/amd-gfx/20260730171754.704049-1-jerry.zuo@amd.com/
> v2: https://lore.kernel.org/amd-gfx/20260806205449.16806-1-jerry.zuo@amd.com/
> v3: https://lore.kernel.org/amd-gfx/20260811003921.1398292-1-jerry.zuo@amd.com/
>
> Changes since v3:
>    - Drop the content-type based ALLM heuristic. ALLM_Mode is now set only
>      for the mandatory Gaming-VRR case (VRR_EN=1 with a sink that advertises
>      ALLM), per HDMI 2.1 Section 7.6.6; it is no longer derived from the
>      content type.
>
> Changes since v2:
>    - Fix coding-style issues in the VTEM info-packet code.
>
> Fangzhi Zuo (3):
>    drm/amd/display: Add 2.1 FreeSync support for AMD VSDB EDID Block
>    drm/amd/display: Add HDMI 2.1 VRR support from HF-VSDB
>    drm/amd/display: Enable HDMI ALLM for Gaming-VRR
>
> Tomasz Pakuła (1):
>    drm/edid: parse HDMI 2.1 gaming (ALLM/VRR) capabilities from HF-VSDB
>
>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |   5 +-
>   .../display/amdgpu_dm/amdgpu_dm_connector.c   |  71 +++++++++++-
>   .../display/amdgpu_dm/amdgpu_dm_freesync.c    |  41 +++++++
>   .../amd/display/modules/inc/mod_info_packet.h |   4 +
>   .../display/modules/info_packet/info_packet.c | 109 ++++++++++++++++++
>   drivers/gpu/drm/drm_edid.c                    |  42 +++++++
>   include/drm/drm_connector.h                   |  47 ++++++++
>   7 files changed, 317 insertions(+), 2 deletions(-)
>
>
> base-commit: de2622bbc20276eaaaafa8fdbd374ace1ced28dc