Em Ter, 2016-08-09 às 14:44 +0200, Maarten Lankhorst escreveu: > Hey, > > Op 08-08-16 om 23:03 schreef Lyude: > > > > Since the watermark calculations for Skylake are still broken, > > we're apt > > to hitting underruns very easily under multi-monitor > > configurations. > > While it would be lovely if this was fixed, it's not. Another > > problem > > that's been coming from this however, is the mysterious issue of > > underruns causing full system hangs. An easy way to reproduce this > > with > > a skylake system: > > > > - Get a laptop with a skylake GPU, and hook up two external > > monitors to > > it > > - Move the cursor from the built-in LCD to one of the external > > displays > > as quickly as you can > > - You'll get a few pipe underruns, and eventually the entire system > > will > > just freeze. > > > > After doing a lot of investigation and reading through the bspec, I > > found the existence of the SAGV, which is responsible for adjusting > > the > > system agent voltage and clock frequencies depending on how much > > power > > we need. According to the bspec: > > > > "The display engine access to system memory is blocked during the > > adjustment time. SAGV defaults to enabled. Software must use the > > GT-driver pcode mailbox to disable SAGV when the display engine is > > not > > able to tolerate the blocking time." > > > > The rest of the bspec goes on to explain that software can simply > > leave > > the SAGV enabled, and disable it when we use interlaced pipes/have > > more > > then one pipe active. > > > > Sure enough, with this patchset the system hangs resulting from > > pipe > > underruns on Skylake have completely vanished on my T460s. > > Additionally, > > the bspec mentions turning off the SAGV with more then one > > pipe enabled > > as a workaround for display underruns. While this patch doesn't > > entirely > > fix that, it looks like it does improve the situation a little bit > > so > > it's likely this is going to be required to make watermarks on > > Skylake > > fully functional. > > I think this patch goes with v9 6/6 and v8 2-5/6. If you're only > updating a single patch it might be better to send it in reply to the > original patch. > > I'm testing the whole series on my prerelease skylake, and running > into this: > > [ 2794.933149] kms_cursor_legacy: starting subtest 2x-flip-vs-cursor- > legacy > [ 2795.813970] [drm:skl_disable_sagv [i915]] *ERROR* Request to > disable SAGV timed out > > Value returned from skl_do_sagv_disable is always 0 for me, even when > I bump the timeout to 15. Yesterday I started testing this series, and I also noticed some visual corruption: while browsing moderately-heavy websites on a maximized Firefox, I could see the desktop background sort of "blinking" in the screen (the background was not supposed to be visible). It looks like the problem was introduced by patch 4, but I can't be 100% sure since sometimes it's a little harder to reproduce it. Still, this is better than the current "X doesn't work" state that we have without the series. > > ~Maarten > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/intel-gfx _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
