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Message-ID: <20091015083023.2f389296@jbarnes-g45> Date: Thu, 15 Oct 2009 08:30:23 -0700 From: Jesse Barnes <jbarnes@...tuousgeek.org> To: Theodore Tso <tytso@....edu> Cc: "Carlos R. Mafra" <crmafra2@...il.com>, Eric Anholt <eric@...olt.net>, linux-kernel@...r.kernel.org, Keith Packard <keithp@...thp.com>, Chris Wilson <chris@...is-wilson.co.uk> Subject: Re: 2.6.32 regression (bisected): Video tearing/glitching with T400 laptops On Wed, 14 Oct 2009 22:26:45 -0400 Theodore Tso <tytso@....edu> wrote: > On Wed, Oct 14, 2009 at 02:22:52PM -0700, Jesse Barnes wrote: > > On Tue, 13 Oct 2009 12:14:26 -0700 > > Jesse Barnes <jbarnes@...tuousgeek.org> wrote: > > > According to the chipset team that form of display corruption is > > > likely related to RAM self-refresh... Sounds like the display > > > plane isn't getting its memory requests serviced fast enough when > > > in self-refresh mode, which might mean we have to program the > > > self-refresh watermarks more aggressively on GM45. > > > > Ok, like any good bug there was more than one thing wrong: > > - we weren't setting up a fence for the object before enabling > > FBC. Chris caught this and posted a patch to > > intel-gfx@...ts.freedesktop.org titled "drm/i915: Install a > > fence register for fbc on g4x" (attached for convenience) > > - turns out we *do* need to set watermarks on G4x, despite some hw > > documentation indicating otherwise, patch for that attached > > > > Hopefully with these two you'll have a solid display and some power > > saving! > > With these two patches (and none of your prior ones) applied to > 2.6.32-rc3, things are definitely better. I'm still seeing a few > glitches (one as mutt was loading my Maildir inbox) and one as I was > typing this message in emacs, but it's at best one minor every 5-10 > minutes. It's rare enough to be at most a wee bit distracting (*lots* > better than before), and I can see the power savings. > > If I need to live with a display glitch every 5-10 minutes or so to > get better power savings, I'll take it.... Oh I think we can do better than that. The hardcoded values I put in for the watermarks are almost certainly wrong. I should be able to reproduce what you're seeing (anything that takes a lot of memory bandwidth will probably cause flicker) and adjust the watermarks to the correct values to avoid that. I'll try to find time in Japan to do that... -- Jesse Barnes, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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