drm/amd/display: Enable HDMI ALLM for Gaming-VRR

Browse source

why:
HDMI 2.1 Auto Low-Latency Mode (ALLM) lets a Source request the Sink's
low-latency mode through the HF-VSIF. HDMI 2.1 Section 7.6.6 requires
that when Gaming-VRR is enabled (VRR_EN=1) and the Sink advertises ALLM
in the SCDS, the Source shall transmit the HF-VSIF and set ALLM_Mode=1.
amdgpu never set ALLM_Mode, so this requirement was not met.

how:
- In update_freesync_state_on_stream(), set ALLM_Mode=1 in the HF-VSIF
  when Gaming-VRR is active (vrr state ACTIVE_VARIABLE/ACTIVE_FIXED,
  i.e. VRR_EN=1) and the sink advertises ALLM, per HDMI 2.1 Section
  7.6.6, and push the updated HF-VSIF (vsp_infopacket) as a stream
  update.
- ALLM is driven by the mandatory Gaming-VRR case.

Signed-off-by: Fangzhi Zuo <Jerry.Zuo@amd.com>
Signed-off-by: Tomasz Pakuła <tomasz.pakula.oficjalny@gmail.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

...

This commit is contained in:

Fangzhi Zuo 2026-07-24 16:01:14 -04:00 • committed by Alex Deucher

parent fa3389c713

commit 8b607d6f54

2 changed files with 33 additions and 1 deletions

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

Download patch file Download diff file Expand all files Collapse all files

5

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

View file

29

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_freesync.c

View file