RE: [External Mail] Re: Test result / finding of "drm/amd/display: Consult MCCS FreeSync cap only if requested & supported"

[Pei-Hsin Yang <peihsiny@valvesoftware.com>]

Hi Michel,

> Note that Pei-Hsin reported an issue when running with my fix at the start of this thread, unfortunately it's still unclear if that's a regression of > my fix or happens even without it (in which case it might be another regression of the MCCS related changes for 7.1).

As I have mentioned earlier, my testing of your patch confirms that it is a regression even without your patch.

There are two reliability matters in most recent FreeSync / MCCS implementation need further clarification from the AMD team.  freesync_capable or MCCS support are inadvertently disabled on some occasions, for example, after HDMI cable hot plug.

1. AMD VSDB EDID parsing via internal dmub communication.
2. AMD MCCS VCP Code helpers.

NOTE: I found these issues after backporting from asdn 7.x to SteamOS 6.16/6.18.  It is verified on Steam Machine.

Thanks,
Pei-Hsin


-----Original Message-----
From: Michel Dänzer <michel.daenzer@mailbox.org> 
Sent: Thursday, June 4, 2026 6:58 AM
To: Alex Deucher <alexdeucher@gmail.com>
Cc: Deucher, Alexander <Alexander.Deucher@amd.com>; Thorsten Leemhuis <regressions@leemhuis.info>; Pei-Hsin Yang <peihsiny@valvesoftware.com>; Wentland, Harry <Harry.Wentland@amd.com>; Li, Sun peng (Leo) <Sunpeng.Li@amd.com>; amd-gfx@lists.freedesktop.org; Linux kernel regressions list <regressions@lists.linux.dev>; Koenig, Christian <Christian.Koenig@amd.com>
Subject: [External Mail] Re: Test result / finding of "drm/amd/display: Consult MCCS FreeSync cap only if requested & supported"

On 6/4/26 15:20, Alex Deucher wrote:
> On Thu, Jun 4, 2026 at 3:59 AM Michel Dänzer <michel.daenzer@mailbox.org> wrote:
>> On 5/29/26 00:02, Deucher, Alexander wrote:
>>>> From: Thorsten Leemhuis <regressions@leemhuis.info> On 5/21/26 
>>>> 09:09, Michel Dänzer wrote:
>>>>>
>>>>> 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?
>>
>> Looks like this regression will make it to 7.1 final?
>>
>> I filed https://gitlab.freedesktop.org/drm/amd/-/work_items/5286 3 weeks ago, and proposed a fix the following week. There's been no reaction by any AMD display developer.
>>
>> This is pretty sad.
> 
> @Wentland, Harry , @Leo (Sunpeng) Li come on guys!  I've picked up 
> Michel's patch and I'll send an update -PR today.

Thanks Alex.


Note that Pei-Hsin reported an issue when running with my fix at the start of this thread, unfortunately it's still unclear if that's a regression of my fix or happens even without it (in which case it might be another regression of the MCCS related changes for 7.1).

An alternative would be reverting the 4 commits d49086491bcb..8dc88c6a5948.


-- 
Earthling Michel Dänzer       \        GNOME / Xwayland / Mesa developer
https://redhat.com             \               Libre software enthusiast