Re: [PATCH v3 00/19] drm/amd: VRR fixes, HDMI Gaming Features

[Harry Wentland <harry.wentland@amd.com>]

On 2026-02-03 13:56, Tomasz Pakuła wrote:
> This patch series tackles a few things:
> - Fixes VRR not detected if monitor uses GTF flag for ranges
>   instead of Range Limits Only
> - Detects if AMD vsdb carries a wider VRR range and uses it instead
> - DP->HDMI PCON changes which includes a module property to override
>   PCON ID check
> - Parses HDMI gaming features in generic drm
> - Reintroduces proper HF-VSIF and VTEM info packets
> - Adds support for Auto Low Latency Mode
> - Adds support for HDMI VRR
> 
> VRR range fixes are simple and fix VRR support for many monitors. They
> close about 5 issues on the amdgpu issue tracker.
> 
> Adaptive Sync over PCON is only available as FreeSync over HDMI. TVs which
> do not support FreeSync, do not have working VRR with DP -> HDMI 2.1
> adapters even though adapters will take care of HDMI VRR info packets.
> 
> I myself validated these changes with my Samsung S95B + Bernhard validated
> on LG C4 + FreeSync-less Sony Bravia 8. I used Alienware AW3423DWF that
> only has HDMI 2.0 to check that FreeSync still triggers properly for
> "older" hardware,
> 
> For missing VRRmax or VRRmax == 0, the upper boundary is the currently
> selected video mode refresh rate. I wasn't sure how best to implement it
> but ended up on a great solution. We first check if maybe there is a VRR
> range in AMD vsdb. If not, rely on limitation of base refresh rate in
> VTEM vsif.
> 
> More history on previous shape of HF-VSIF and VTEM in their respective
> patches but the info packets were previously included in the driver code.
> HF-VSIF was improperly handled and VTEM doesn't seem to have been plumbed
> as it had no use before. I recoded these and this code should be much
> easier to understand and maintain.
> 
> ALLM support uses the info from EDID to determine if ALLM is supported by
> sink and if that's the case, always signals for ALLM to be enabled. In PC
> use, be it for gaming, desktop use, work etc. we always want the lowest
> latency and less processing + possibly higher available refresh rates when
> gaming mode is turned on.
> 
> HDMI VRR support relies on sending VTEM info packet in place of FreeSync
> info packets. Though VTEM has it's own place in the info packet pipeline,
> I didn't touch it as it already replaces FreeSync info packets. If there's
> a need to change this, please let me know for v2.
> 
> Both features were tested and work just like they were intended to. Gaming
> mode is automatically triggered and HDMI VRR is used in place of FreeSync
> (if available). This HDMI VRR preference actually fixes VRR-induced
> flickering on many TVs (S95B in my case) with somehow subpar
> FreeSync implementation.
> 
> I still think it's better to not force users to search for solutions
> manually especially since it seems like DP and eDP don't save info about
> FreeSync version and completely rely on basic VRR support.
> This would then be mirrored.
> 
> There's still an issue with some TVs behaving like a mode change is
> happening when VRR is triggered and I'd like to maybe tackle this too. When
> using HDMI through PCON, VRR is always active, like it's in
> VRR_STATE_ACTIVE_FIXED mode. This makes my TV much nicer to use and
> replication this behavior would be worthwhile IMO.
> 
> Everything in this patch series has been based on already public
> code/knowledge or trying things out until they work/break.
> 

Thanks for your thorough patch series. Really appreciate it.

I left comments on a few patches.

Patches 1, 3, 4, 6, 7, 9, 10, 12, 13, and 15 are
Reviewed-by: Harry Wentland <harry.wentland@amd.com>

I can't currently comment on patches 8, 11, 14, 17, 18.

Harry

> This patch series supersedes previous patches/series:
> https://lore.kernel.org/amd-gfx/20251209231107.1968472-1-tomasz.pakula.oficjalny@gmail.com/
> https://lore.kernel.org/amd-gfx/20260113214104.146856-1-tomasz.pakula.oficjalny@gmail.com/
> https://lore.kernel.org/amd-gfx/20260113183540.86266-1-tomasz.pakula.oficjalny@gmail.com/
> 
> Built on top of amd-staging-drm-next
> 
> Changes in v2:
> - Updated BRR max value to 1023 after testing one by one. This should've
>   been obvious since 1023 is the max value for a 10-bit field
> - Fixed some comments, to silence "not a kernel doc" warning
> - Considered ALLM comments from Michel Dänzer, Daniel Stone and
>   Jani Nikula. ALLM is now triggered if either VRR is active or Content
>   Type Hint is set to "Game". Content type hint is already supported by
>   amdgpu and fully plumbed.
> - Added module parameter for controlling ALLM trigger behavior. Now it can
>   be configured to never trigger ALLM, trigger with VRR/Game (default) or
>   be always forced on.
> - Added HDMI VRR desktop mode module parameter, which is on by default.
>   This mimics how FreeSync is handeled on Windows and this fixes a lot of
>   issues with unwanted screen blanking and glitches around entering/exiting
>   VRR mode.
> - Moved hdmi vic mode check to one central function to avoid checking for
>   3D and ALLM in different places which could sometimes break the logic for
>   translating HDMI VIC modes into CTA vic modes (when such translation 
>   is needed).
>   
> Changes in v3:
> - Fixed wonky English
> - Less struct traversal in helper functions
> - Fixed possible NULL pointer dereference while checking if ALLM support is
>   indicated in edid_caps of local_sink
> - Fixed ALLM bit assignment overriding 3D bit data in HF-VSIF
> - Fixed assignment of the upper 2 bits of BRR in VTEM
> 
> Tomasz Pakuła (19):
>   drm/amd/display: Return if DisplayID not found in parse_amd_vsdb()
>   drm/amd/display: Refactor amdgpu_dm_update_freesync_caps()
>   drm/amd/display: Check for VRR range in CEA AMD vsdb
>   drm/amd/display: Use bigger VRR range if found in AMD vsdb
>   drm/amd/display: Refactor PCON VRR compatibility check
>   drm/amd/display: Add PCON VRR ID check override
>   drm/amd/display: Add CH7218 PCON ID
>   drm/edid: Parse more info from HDMI Forum vsdb
>   drm/amd/display: Rename PCON adaptive sync types
>   drm/amd/display: Enable HDMI VRR over PCON
>   drm/amd/display: Support HDMI VRRmax=0
>   drm/amd/display: Build HDMI vsif in correct slot
>   drm/amd/display: Save HDMI gaming info to edid caps
>   drm/amd/display: Restore ALLM support in HDMI vsif
>   drm/amd/display: Trigger ALLM if it's available
>   drm/amd/display: Add parameter to control ALLM behavior
>   drm/amd/display: Reintroduce VTEM info frame
>   drm/amd/display: Enable HDMI VRR
>   drm/amd/display: Add HDMI VRR desktop mode
> 
>  drivers/gpu/drm/amd/amdgpu/amdgpu.h           |   2 +
>  drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c       |  27 +-
>  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 207 ++++++++---
>  .../amd/display/amdgpu_dm/amdgpu_dm_helpers.c |  49 ++-
>  .../gpu/drm/amd/display/dc/core/dc_resource.c |   5 +-
>  drivers/gpu/drm/amd/display/dc/dc.h           |   1 +
>  drivers/gpu/drm/amd/display/dc/dc_types.h     |   7 +-
>  drivers/gpu/drm/amd/display/dc/dm_helpers.h   |   2 +-
>  .../amd/display/include/ddc_service_types.h   |   1 +
>  .../amd/display/modules/freesync/freesync.c   |   4 +
>  .../amd/display/modules/inc/mod_info_packet.h |  18 +-
>  .../display/modules/info_packet/info_packet.c | 342 ++++++++++++------
>  drivers/gpu/drm/amd/include/amd_shared.h      |   6 +
>  drivers/gpu/drm/drm_edid.c                    |  41 ++-
>  include/drm/drm_connector.h                   |  47 +++
>  15 files changed, 559 insertions(+), 200 deletions(-)
>