Public > -----Original Message----- > From: Thorsten Leemhuis <[email protected]> > Sent: Thursday, May 28, 2026 7:17 AM > To: Michel Dänzer <[email protected]>; Pei-Hsin Yang > <[email protected]> > Cc: [email protected]; Linux kernel regressions list > <[email protected]>; Deucher, Alexander > <[email protected]>; Koenig, Christian > <[email protected]> > Subject: Re: [External Mail] Re: Test result / finding of "drm/amd/display: > Consult MCCS FreeSync cap only if requested & supported" > > [+Alex +Christian] > > On 5/21/26 09:09, Michel Dänzer wrote: > > 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. > > Yeah, that would be good. Makes me wonder how the rough plan to realize > this looks like? Sounds like Michael's patch[1] that was discussed here is > not a > good option? Reminder, Linus ideally wants known regression fixed by -rc6, > which is why I'm asking.
@Wentland, Harry can you sort this out for next week's -fixes PR? Alex > > Ciao, Thorsten > > [1] > https://lore.kernel.org/amd-gfx/20260518154809.660061-1- > [email protected]/
