[PATCH 20/23] drm/amd/display: Disables dynamic memory clock switching in games

[Alex Deucher]

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 at amd.com> 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 at amd.com>
> Sent: June 13, 2022 8:42 AM
> To: Michel Dänzer <michel.daenzer at mailbox.org>; Mahfooz, Hamza <Hamza.Mahfooz at amd.com>; amd-gfx at lists.freedesktop.org
> Cc: Wang, Chao-kai (Stylon) <Stylon.Wang at amd.com>; Liu, HaoPing (Alan) <HaoPing.Liu at amd.com>; Li, Sun peng (Leo) <Sunpeng.Li at amd.com>; Lakha, Bhawanpreet <Bhawanpreet.Lakha at amd.com>; Zhuo, Qingqing (Lillian) <Qingqing.Zhuo at amd.com>; Siqueira, Rodrigo <Rodrigo.Siqueira at amd.com>; Li, Roman <Roman.Li at amd.com>; Chiu, Solomon <Solomon.Chiu at amd.com>; Zuo, Jerry <Jerry.Zuo at amd.com>; Pillai, Aurabindo <Aurabindo.Pillai at amd.com>; Vanzylldejong, Harry <Harry.Vanzylldejong at amd.com>; Lin, Wayne <Wayne.Lin at amd.com>; Wentland, Harry <Harry.Wentland at amd.com>; Gutierrez, Agustin <Agustin.Gutierrez at amd.com>; Kotarac, Pavle <Pavle.Kotarac at amd.com>
> 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 at amd.com>
> >>
> >> [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.
> >
> >
> --
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