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 <alexdeucher@xxxxxxxxx> > Sent: June 13, 2022 10:34 AM > To: Vanzylldejong, Harry <Harry.Vanzylldejong@xxxxxxx> > Cc: VURDIGERENATARAJ, CHANDAN <CHANDAN.VURDIGERENATARAJ@xxxxxxx>; Michel Dänzer <michel.daenzer@xxxxxxxxxxx>; Mahfooz, Hamza <Hamza.Mahfooz@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx; Wang, Chao-kai (Stylon) <Stylon.Wang@xxxxxxx>; Liu, HaoPing (Alan) <HaoPing.Liu@xxxxxxx>; Li, Sun peng (Leo) <Sunpeng.Li@xxxxxxx>; Wentland, Harry <Harry.Wentland@xxxxxxx>; Zhuo, Qingqing (Lillian) <Qingqing.Zhuo@xxxxxxx>; Siqueira, Rodrigo <Rodrigo.Siqueira@xxxxxxx>; Li, Roman <Roman.Li@xxxxxxx>; Chiu, Solomon <Solomon.Chiu@xxxxxxx>; Zuo, Jerry <Jerry.Zuo@xxxxxxx>; Pillai, Aurabindo <Aurabindo.Pillai@xxxxxxx>; Lin, Wayne <Wayne.Lin@xxxxxxx>; Lakha, Bhawanpreet <Bhawanpreet.Lakha@xxxxxxx>; Gutierrez, Agustin <Agustin.Gutierrez@xxxxxxx>; Kotarac, Pavle <Pavle.Kotarac@xxxxxxx> > 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 <Harry.Vanzylldejong@xxxxxxx> 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 <CHANDAN.VURDIGERENATARAJ@xxxxxxx> >> Sent: June 13, 2022 8:42 AM >> To: Michel Dänzer <michel.daenzer@xxxxxxxxxxx>; Mahfooz, Hamza >> <Hamza.Mahfooz@xxxxxxx>; amd-gfx@xxxxxxxxxxxxxxxxxxxxx >> Cc: Wang, Chao-kai (Stylon) <Stylon.Wang@xxxxxxx>; Liu, HaoPing (Alan) >> <HaoPing.Liu@xxxxxxx>; Li, Sun peng (Leo) <Sunpeng.Li@xxxxxxx>; Lakha, >> Bhawanpreet <Bhawanpreet.Lakha@xxxxxxx>; Zhuo, Qingqing (Lillian) >> <Qingqing.Zhuo@xxxxxxx>; Siqueira, Rodrigo <Rodrigo.Siqueira@xxxxxxx>; >> Li, Roman <Roman.Li@xxxxxxx>; Chiu, Solomon <Solomon.Chiu@xxxxxxx>; >> Zuo, Jerry <Jerry.Zuo@xxxxxxx>; Pillai, Aurabindo >> <Aurabindo.Pillai@xxxxxxx>; Vanzylldejong, Harry >> <Harry.Vanzylldejong@xxxxxxx>; Lin, Wayne <Wayne.Lin@xxxxxxx>; >> Wentland, Harry <Harry.Wentland@xxxxxxx>; Gutierrez, Agustin >> <Agustin.Gutierrez@xxxxxxx>; Kotarac, Pavle <Pavle.Kotarac@xxxxxxx> >> 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 <harry.vanzylldejong@xxxxxxx> >>>> >>>> [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
