> Note that some kind of short-term solution is needed for the regression(s) in > 7.1-rc.
Here is my suggestion as a short-term workaround:
- Just refer to the vsdb_info data structure to set the value of
freesync_capable. freesync_mccs_vcp_code = 0 doesn't mean FreeSync is not
supported.
- Check both freesync_supported and freesync_mccs_vcp_code along with
do_mccs to call dm_helpers_mccs_vcp_set().
- Note that MCCS command over DDC might be failed at runtime, but at
least, it will not inadvertently disable the VRR if (1) sink is FreeSync
supported but vcp_code = 0, or (2) dm_helpers_read_mccs_cap() failed
intermittently at runtime.
Patch created based on commit 53f0235c0284fc676d1510a460e1c6c111de3ea1 is
attached as a reference for AMD team to review.
commit 53f0235c0284fc676d1510a460e1c6c111de3ea1 (HEAD -> amd-staging-drm-next,
origin/amd-staging-drm-next, origin/HEAD)
Thanks
Pei-Hsin
-----Original Message-----
From: Michel Dänzer <[email protected]>
Sent: Thursday, May 21, 2026 12:10 AM
To: Pei-Hsin Yang <[email protected]>
Cc: [email protected]
Subject: Re: [External Mail] Re: Test result / finding of "drm/amd/display:
Consult MCCS FreeSync cap only if requested & supported"
On 5/20/26 17:54, Pei-Hsin Yang wrote:
>
>> Tested with 3 HDMI sinks with different FreeSync/HDMI VRR capabilities. I
>> saw one case that a FreeSync sink (Dell S2721HS) with E6h VCP code supported
>> was detected as FreeSync capable at beginning but identified as not FreeSync
>> capable later – after do_mccs is changed from true to false.
>
>>> And that doesn't happen without my patch applied?
>
> There are other issues without your patch applied. One issue is that if a
> FreeSync capable sink with MCCS VCP Code = 0 (mostly are TVs), it will be
> detected as not FreeSync supported and VRR will be disabled.
That sounds similar to https://gitlab.freedesktop.org/drm/amd/-/work_items/5286
.
I was wondering if the specific issue you described above with Dell S2721HS is
reproducible without my patch though, in which case it might be a separate
regression (and wouldn't speak against merging my patch).
>>> TBH I don't really want to be fixing the regression I hit, I'd prefer the
>>> AMD display team to handle it.
>
> Yes, agreed. As FreeSync MCCS support has immediate impacts to Valve's Steam
> devices, I will work with AMD display team to handle it. HDMI 2.1 VRR and
> VTEM packet sending support need to be included as well.
Note that some kind of short-term solution is needed for the regression(s) in
7.1-rc.
--
Earthling Michel Dänzer \ GNOME / Xwayland / Mesa developer
https://redhat.com \ Libre software enthusiast
asdn-freesync-mccs-caps-use-vsdb.patch
Description: asdn-freesync-mccs-caps-use-vsdb.patch
