On Tue, Sep 19, 2017 at 11:06:52AM +0200, Maarten Lankhorst wrote:
> Op 18-09-17 om 17:03 schreef Ville Syrjälä:
> > On Mon, Sep 18, 2017 at 12:12:50PM +0200, Maarten Lankhorst wrote:
> >> Commit b44d5c0c105a ("drm/i915: Always wait for flip_done, v2.") removed
> >> the call to wait_for_vblanks and replaced it with flip_done.
> >>
> >> Unfortunately legacy_cursor_update was unset too late, and the
> >> replacement call drm_atomic_helper_wait_for_flip_done() was
> >> a noop. Make sure that its unset before setup_commit() is
> >> called to fix this issue.
> >>
> >> Changes since v1:
> >> - Force vblank wait for watermarks not yet converted to atomic too. (Ville)
> >> - Use for_each_new_intel_crtc_in_state. (Ville)
> >>
> >> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> >> Fixes: b44d5c0c105a ("drm/i915: Always wait for flip_done, v2.")
> >> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=102675
> >> Testcase: kms_cursor_crc
> >> Cc: Daniel Vetter <daniel.vetter@xxxxxxxx>
> >> Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> >> Reported-by: Marta Löfstedt <marta.lofstedt@xxxxxxxxx>
> >> Cc: Marta Löfstedt <marta.lofstedt@xxxxxxxxx>
> >> Tested-by: Marta Löfstedt <marta.lofstedt@xxxxxxxxx>
> >> Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> >> ---
> >> drivers/gpu/drm/i915/intel_display.c | 45 +++++++++++++++++++++---------------
> >> 1 file changed, 26 insertions(+), 19 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> >> index 8599e425abb1..8d051256da1e 100644
> >> --- a/drivers/gpu/drm/i915/intel_display.c
> >> +++ b/drivers/gpu/drm/i915/intel_display.c
> >> @@ -12517,21 +12517,10 @@ static int intel_atomic_commit(struct drm_device *dev,
> >> struct drm_i915_private *dev_priv = to_i915(dev);
> >> int ret = 0;
> >>
> >> - ret = drm_atomic_helper_setup_commit(state, nonblock);
> >> - if (ret)
> >> - return ret;
> >> -
> >> drm_atomic_state_get(state);
> >> i915_sw_fence_init(&intel_state->commit_ready,
> >> intel_atomic_commit_ready);
> >>
> >> - ret = intel_atomic_prepare_commit(dev, state);
> >> - if (ret) {
> >> - DRM_DEBUG_ATOMIC("Preparing state failed with %i\n", ret);
> >> - i915_sw_fence_commit(&intel_state->commit_ready);
> >> - return ret;
> >> - }
> >> -
> >> /*
> >> * The intel_legacy_cursor_update() fast path takes care
> >> * of avoiding the vblank waits for simple cursor
> >> @@ -12540,19 +12529,37 @@ static int intel_atomic_commit(struct drm_device *dev,
> >> * updates happen during the correct frames. Gen9+ have
> >> * double buffered watermarks and so shouldn't need this.
> >> *
> >> - * Do this after drm_atomic_helper_setup_commit() and
> >> - * intel_atomic_prepare_commit() because we still want
> >> - * to skip the flip and fb cleanup waits. Although that
> >> - * does risk yanking the mapping from under the display
> >> - * engine.
> >> + * Unset state->legacy_cursor_update before the call to
> >> + * drm_atomic_helper_setup_commit() because otherwise
> >> + * drm_atomic_helper_wait_for_flip_done() is a noop and
> >> + * we get FIFO underruns because we didn't wait
> >> + * for vblank.
> >> *
> >> * FIXME doing watermarks and fb cleanup from a vblank worker
> >> * (assuming we had any) would solve these problems.
> >> */
> >> - if (INTEL_GEN(dev_priv) < 9)
> >> - state->legacy_cursor_update = false;
> >> + if (INTEL_GEN(dev_priv) < 9 && state->legacy_cursor_update) {
> >> + struct intel_crtc_state *new_crtc_state;
> >> + struct intel_crtc *crtc;
> >> + int i;
> >> +
> >> + for_each_new_intel_crtc_in_state(intel_state, crtc, new_crtc_state, i)
> >> + if (new_crtc_state->wm.need_postvbl_update ||
> >> + new_crtc_state->update_wm_post)
> >> + state->legacy_cursor_update = false;
> > Hmm. I guess that's better. But I still don't see why you want to change
> > this bit of code in this patch. AFAICS it's got nothing to do with the fix
> > itself, and instead it's just trying to optimize some cursor updates
> > that were kicked over to the slow path. Or am I missing something?
>
> We accidentally removed the vblank wait for the slowpath, but I don't think we should reintroduce the vblank except where we need it..
IMO any regression fix should ideally get us back exactly where we were.
--
Ville Syrjälä
Intel OTC
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