Deucher, Alexander wrote: >> -----Original Message----- From: amd-gfx >> [mailto:amd-gfx-bounces at lists.freedesktop.org] On Behalf Of Andy >> Furniss Sent: Sunday, November 06, 2016 3:31 PM To: Zhu, Rex; >> Deucher, Alexander; amd-gfx at lists.freedesktop.org Subject: Re: >> [PATCH] drm/amdgpu: set bypass mode when uvd is idle. >> >> Zhu, Rex wrote: >>>>>> Is there any harm in just always putting it into bypass >>>>>> mode or does it interact badly with PG? Presumably it does >>>>>> (otherwise we wouldn't need this patch), it would be good >>>>>> to note why. >>> >>> Rex: when UVD PG enabled, DCLK/VCLK will be turn off when uvd is >>> idle(DCLK=OFF). If we set bypass mode=1, dclk/vclk will be >>> bypassed to an external â??Bypassâ?? clock(DCLK = 100MHz) >>> >>> So it is unnecessary to set bypass mode when PG enabled. >>> >>> +uvd_v5_0_set_bypass_mode(adev, !enable); This change is because >>> tom's commit 72cb64c1f6a3a8129af341e90418a687c4971a40 Fix the >>> sequence of UVD powergate function in smu7_clockgating.c. >> >> I was about to file a bug till I tried this which fixes UVD perf on >> my R9285 + agd5f drm-next-4.10-wip. >> >> Additional unrelated question = I notice that UVD does not seem to >> set other clocks quite high enough when used. >> >> For playback the vo may bump things up a bit, but even then it can >> be a bit borderline for playing high bitrate UHD with powerplay on >> auto. >> >> Pure decode benchmarks like >> >> ffmpeg -hwaccel vdpau -i high-bitrate-2160p60-vid -pix_fmt nv12 -f >> null - >> >> go from 63 -> 81 fps, powerplay auto -> high. > > The UVD and gfx clocks are separate. The gfx load for video decode > operations is not generally great enough (CSC and maybe scaling) to > generate enough gfx load to boost the gfx clocks to their highest > level. We plan to add an API to allow userspace applications to > request a minimum floor for specific contexts, but it hasn't been > implemented yet. This is useful if you are trying to hit maximum > decode rates, but may not always be the best choice for power usage. > You really only want to set the clocks high enough to hit the target > frame rate. > > Alex OK, thanks for the info.
