On Mon, Oct 22, 2012 at 12:55:55PM +0200, Daniel Vetter wrote: > The overlay on the i830M has a peculiar failure mode: It works the > first time around after boot-up, but consistenly hangs the second time > it's used. > > Chris Wilson has dug out a nice errata: > > "1.5.12 Clock Gating Disable for Display Register > Address Offset: 06200h?06203h > > "Bit 3 > Ovrunit Clock Gating Disable. > 0 = Clock gating controlled by unit enabling logic > 1 = Disable clock gating function > DevALM Errata ALM049: Overlay Clock Gating Must be Disabled: Overlay > & L2 Cache clock gating must be disabled in order to prevent device > hangs when turning off overlay.SW must turn off Ovrunit clock gating > (6200h) and L2 Cache clock gating (C8h)." > > Now I've nowhere found that 0xc8 register and hence couldn't apply the > l2 cache workaround. But I've remembered that part of the magic that > the OVERLAY_ON/OFF commands are supposed to do is to rearrange cache > allocations so that the overlay scaler has some scratch space. > > And while pondering how that could explain the hang the 2nd time we > enable the overlay, I've remembered that the old ums overlay code did > _not_ issue the OVERLAY_OFF cmd. > > And indeed, disabling the OFF cmd results in the overlay working > flawlessly, so I guess we can workaround the lack of the above > workaround by simply never disabling the overlay engine once it's > enabled. > > v2: Add a comment in the code. > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=47827 > Cc: stable at vger.kernel.org > Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch> Tested-by: Rhys <rhyspuk at gmail.com> > --- > drivers/gpu/drm/i915/intel_overlay.c | 14 +++++++++++--- > 1 file changed, 11 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/i915/intel_overlay.c b/drivers/gpu/drm/i915/intel_overlay.c > index 555912f..e3b095f 100644 > --- a/drivers/gpu/drm/i915/intel_overlay.c > +++ b/drivers/gpu/drm/i915/intel_overlay.c > @@ -342,9 +342,17 @@ static int intel_overlay_off(struct intel_overlay *overlay) > intel_ring_emit(ring, flip_addr); > intel_ring_emit(ring, MI_WAIT_FOR_EVENT | MI_WAIT_FOR_OVERLAY_FLIP); > /* turn overlay off */ > - intel_ring_emit(ring, MI_OVERLAY_FLIP | MI_OVERLAY_OFF); > - intel_ring_emit(ring, flip_addr); > - intel_ring_emit(ring, MI_WAIT_FOR_EVENT | MI_WAIT_FOR_OVERLAY_FLIP); > + if (IS_I830(dev)) { > + /* Workaround: Don't disable the overlay fully, since otherwise > + * it dies on the next OVERLAY_ON cmd. */ > + intel_ring_emit(ring, MI_NOOP); > + intel_ring_emit(ring, MI_NOOP); > + intel_ring_emit(ring, MI_NOOP); > + } else { > + intel_ring_emit(ring, MI_OVERLAY_FLIP | MI_OVERLAY_OFF); > + intel_ring_emit(ring, flip_addr); > + intel_ring_emit(ring, MI_WAIT_FOR_EVENT | MI_WAIT_FOR_OVERLAY_FLIP); > + } > intel_ring_advance(ring); > > return intel_overlay_do_wait_request(overlay, intel_overlay_off_tail); > -- > 1.7.11.4 > -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch
