At Wed, 29 Feb 2012 23:54:46 +0000, Chris Wilson wrote: > > On Tue, 28 Feb 2012 07:43:55 +0100, Takashi Iwai <tiwai at suse.de> wrote: > > At Mon, 27 Feb 2012 14:08:28 +0100, > > Takashi Iwai wrote: > > > > > > At Mon, 27 Feb 2012 12:17:57 +0000, > > > Chris Wilson wrote: > > > > > > > > On Mon, 27 Feb 2012 12:39:24 +0100, Takashi Iwai <tiwai at suse.de> wrote: > > > > > It seems that writing DSPSURF in intel_flush_display_plane() causes > > > > > the blank screen on some old laptops like Dell D630 with 965GM. > > > > > Since this operation is needed only for ILK+, make it conditional. > > > > > > > > The specs say that DSPASURF is the latch register for updates of the DSPA > > > > registers on gen4 (including 965gm) as well. Presumably the bug is that > > > > we only partially update the DSPA registers prior to the first call to > > > > intel_flush_display_plane() which this papers over by disabling the > > > > update until a valid address is written to DSPASURF. And there is such a > > > > spurious call to intel_enable_plane() prior to us setting a valid > > > > scanout surface: > > > > > > Sounds reasonable. FWIW, the change was first introduced in commit > > > [b24e7179: drm/i915: add pipe/plane enable/disable functions], > > > then in commit [efc2924e: drm/i915: Call intel_enable_plane from > > > i9xx_crtc_mode_set (again)], it's placed into i9xx_crtc_mode_set(). > > > > > > This explains the fact that it was discovered only on old machines > > > as i9xx_crtc_mode_set() is the only crtc_mode_set op calling > > > intel_enable_plane(). > > > > > > BTW, the bisection leaded to a merge commit, so the bug is really > > > depending on the activation path or timing. > > > > > > I'll ask a tester to try your patch. > > > > He reported back that it reduces the failure rate but doesn't fix > > completely. Still get a blank screen in 20% rate. > > > > Any other clue? > > I haven't yet found anything else in the same vein as this, but the > 965gm does ring a warning bell for this recent regression: > > commit 5ca0c34ae28344b6b4ca3036bc82f89c8db16a59 > Author: Dave Airlie <airlied at redhat.com> > Date: Thu Feb 23 15:33:40 2012 +0000 > > drm/i915: fix mode set on load pipe. (v2) > > Booted my i965 machine and it started printing the unsupported pixel > format of 0 message (once I added content to it). > > Oh looksie here, we pass 0. fix. > > v2: compile it. > > Buzilla: https://bugs.freedesktop.org/show_bug.cgi?id=45966 > > Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch> > Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk> > Signed-off-by: Dave Airlie <airlied at redhat.com> > Signed-off-by: Jesse Barnes <jbarnes at virtuousgeek.org> > > which is currently sitting in airlied/drm-fixes. Hm, this must be irrelevant (inapplicable) because the tests were done with 3.1, 3.2 (and SLE11-SP2 kernels which has backports from 3.3-rc2 but without these fixes). The bug seems to have been introduced between 3.0 and 3.1. thanks, Takashi
