This seems to be a case of a Windows-centric commit description that doesn't completely make sense for Linux.
The code-change doesn't currently affect any behavior on Linux. It just lays the groundwork in DC to allow an implementation to do a memory-clock switching decision based around VRR support. In short, this won't be a problem for us at this point. Might be better to change the subject line and commit description to reflect that: "drm/amd/display: Add vrr_active_variable to dc_stream_update [Why] The display driver on some OSes need to track it in order to perform memory clock switching decisions." ... or something like the above. Harry On 2022-06-13 10:52, Vanzylldejong, Harry wrote: > [AMD Official Use Only - General] > > +@Clark, Felipe > > -----Original Message----- > From: Alex Deucher <[email protected]> > Sent: June 13, 2022 10:34 AM > To: Vanzylldejong, Harry <[email protected]> > Cc: VURDIGERENATARAJ, CHANDAN <[email protected]>; Michel > Dänzer <[email protected]>; Mahfooz, Hamza <[email protected]>; > [email protected]; Wang, Chao-kai (Stylon) <[email protected]>; > Liu, HaoPing (Alan) <[email protected]>; Li, Sun peng (Leo) > <[email protected]>; Wentland, Harry <[email protected]>; Zhuo, > Qingqing (Lillian) <[email protected]>; Siqueira, Rodrigo > <[email protected]>; Li, Roman <[email protected]>; Chiu, Solomon > <[email protected]>; Zuo, Jerry <[email protected]>; Pillai, Aurabindo > <[email protected]>; Lin, Wayne <[email protected]>; Lakha, > Bhawanpreet <[email protected]>; Gutierrez, Agustin > <[email protected]>; Kotarac, Pavle <[email protected]> > Subject: Re: [PATCH 20/23] drm/amd/display: Disables dynamic memory clock > switching in games > > It should be noted that FAMS is an additional feature to enable mclk > switching in more marginal cases than would normally be possible. > > Alex > > On Mon, Jun 13, 2022 at 9:32 AM Vanzylldejong, Harry > <[email protected]> wrote: >> >> [AMD Official Use Only - General] >> >> Hi Chandan, >> >> When using Firmware Assisted Memory clock Switching (FAMS), when the >> memory clock is switched the frame rate is dropped for at least 1 frame, >> sometimes 2-3 frames to make the V-Blank long enough to handle the period >> where the GDDR6 memory is unavailable when the memory clock switches. >> This drop may be noticeable by gamers, especially if the memory clock >> wants to change it's clock rate several times a second, which is what we >> observed just on the desktop. >> To guarantee best game performance, we disable FAMS during game play. >> >> Harry >> >> >> -----Original Message----- >> From: VURDIGERENATARAJ, CHANDAN <[email protected]> >> Sent: June 13, 2022 8:42 AM >> To: Michel Dänzer <[email protected]>; Mahfooz, Hamza >> <[email protected]>; [email protected] >> Cc: Wang, Chao-kai (Stylon) <[email protected]>; Liu, HaoPing (Alan) >> <[email protected]>; Li, Sun peng (Leo) <[email protected]>; Lakha, >> Bhawanpreet <[email protected]>; Zhuo, Qingqing (Lillian) >> <[email protected]>; Siqueira, Rodrigo <[email protected]>; >> Li, Roman <[email protected]>; Chiu, Solomon <[email protected]>; >> Zuo, Jerry <[email protected]>; Pillai, Aurabindo >> <[email protected]>; Vanzylldejong, Harry >> <[email protected]>; Lin, Wayne <[email protected]>; >> Wentland, Harry <[email protected]>; Gutierrez, Agustin >> <[email protected]>; Kotarac, Pavle <[email protected]> >> Subject: RE: [PATCH 20/23] drm/amd/display: Disables dynamic memory >> clock switching in games >> >> Hi, >> >> Can you please elaborate on why dynamic memory clock switching can affect >> Game performance? >> >> BR, >> Chandan V N >> >> >>> On 2022-06-10 22:52, Hamza Mahfooz wrote: >>>> From: Harry VanZyllDeJong <[email protected]> >>>> >>>> [WHY] >>>> Game performace may be affected if dynamic memory clock switching >>>> is enabled while playing games. >>>> >>>> [HOW] >>>> Propagate the vrr active state to dirty bit so that on mode set it >>>> disables dynamic memory clock switching. >>> >>> So dynamic memory clock switching will be disabled whenever VRR is enabled? >>> >>> Note that there is ongoing discussion about how Wayland compositors could >>> usefully keep VRR enabled all the time, as opposed to only while >there's a >>> fullscreen application like a game. So "VRR is enabled" likely won't be >>> equivalent to "game is running" in the long term. >>> >>> >> -- >> Earthling Michel Dänzer | https://redhat.com/>>> >> Libre software enthusiast | Mesa and Xwayland developer
