Re: [RFC PATCH 1/5] drm/i915: Always wait for flip_done

Daniel Vetter
2017-09-04T07:30:26Z

On Thu, Aug 31, 2017 at 05:18:06PM +0200, Maarten Lankhorst wrote:
> Op 30-08-17 om 15:40 schreef Daniel Vetter:
> > On Wed, Aug 30, 2017 at 02:54:28PM +0200, Maarten Lankhorst wrote:
> >> Op 30-08-17 om 14:43 schreef Daniel Vetter:
> >>> On Wed, Aug 30, 2017 at 02:17:48PM +0200, Maarten Lankhorst wrote:
> >>>> The next commit removes the wait for flip_done in in
> >>>> drm_atomic_helper_commit_cleanup_done, but we need it for the tests
> >>>> to pass. Instead of using complicated vblank tracking which ends
> >>>> up being ignored anyway, call the correct atomic helper. :)
> >>>>
> >>>> RFC because I'm not completely sure what we want to do with the vblank waiting,
> >>>> I think for now this patch is the right way to go until we decide because it
> >>>> preserves the status quo when drm_crtc_commit was introduced.
> >>>>
> >>>> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> >>>> ---
> >>>> drivers/gpu/drm/i915/i915_drv.h | 3 +-
> >>>> drivers/gpu/drm/i915/intel_display.c | 83 +++---------------------------------
> >>>> 2 files changed, 8 insertions(+), 78 deletions(-)
> >>>>
> >>>> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> >>>> index cbbafbfb0a55..de19621864a9 100644
> >>>> --- a/drivers/gpu/drm/i915/i915_drv.h
> >>>> +++ b/drivers/gpu/drm/i915/i915_drv.h
> >>>> @@ -707,8 +707,7 @@ struct drm_i915_display_funcs {
> >>>> struct drm_atomic_state *old_state);
> >>>> void (*crtc_disable)(struct intel_crtc_state *old_crtc_state,
> >>>> struct drm_atomic_state *old_state);
> >>>> - void (*update_crtcs)(struct drm_atomic_state *state,
> >>>> - unsigned int *crtc_vblank_mask);
> >>>> + void (*update_crtcs)(struct drm_atomic_state *state);
> >>>> void (*audio_codec_enable)(struct drm_connector *connector,
> >>>> struct intel_encoder *encoder,
> >>>> const struct drm_display_mode *adjusted_mode);
> >>>> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> >>>> index 52c73b4dabaa..3f3cb96aa11e 100644
> >>>> --- a/drivers/gpu/drm/i915/intel_display.c
> >>>> +++ b/drivers/gpu/drm/i915/intel_display.c
> >>>> @@ -12114,73 +12114,10 @@ u32 intel_crtc_get_vblank_counter(struct intel_crtc *crtc)
> >>>> return dev->driver->get_vblank_counter(dev, crtc->pipe);
> >>>> }
> >>>>
> >>>> -static void intel_atomic_wait_for_vblanks(struct drm_device *dev,
> >>>> - struct drm_i915_private *dev_priv,
> >>>> - unsigned crtc_mask)
> >>>> -{
> >>>> - unsigned last_vblank_count[I915_MAX_PIPES];
> >>>> - enum pipe pipe;
> >>>> - int ret;
> >>>> -
> >>>> - if (!crtc_mask)
> >>>> - return;
> >>>> -
> >>>> - for_each_pipe(dev_priv, pipe) {
> >>>> - struct intel_crtc *crtc = intel_get_crtc_for_pipe(dev_priv,
> >>>> - pipe);
> >>>> -
> >>>> - if (!((1 << pipe) & crtc_mask))
> >>>> - continue;
> >>>> -
> >>>> - ret = drm_crtc_vblank_get(&crtc->base);
> >>>> - if (WARN_ON(ret != 0)) {
> >>>> - crtc_mask &= ~(1 << pipe);
> >>>> - continue;
> >>>> - }
> >>>> -
> >>>> - last_vblank_count[pipe] = drm_crtc_vblank_count(&crtc->base);
> >>>> - }
> >>>> -
> >>>> - for_each_pipe(dev_priv, pipe) {
> >>>> - struct intel_crtc *crtc = intel_get_crtc_for_pipe(dev_priv,
> >>>> - pipe);
> >>>> - long lret;
> >>>> -
> >>>> - if (!((1 << pipe) & crtc_mask))
> >>>> - continue;
> >>>> -
> >>>> - lret = wait_event_timeout(dev->vblank[pipe].queue,
> >>>> - last_vblank_count[pipe] !=
> >>>> - drm_crtc_vblank_count(&crtc->base),
> >>>> - msecs_to_jiffies(50));
> >>>> -
> >>>> - WARN(!lret, "pipe %c vblank wait timed out\n", pipe_name(pipe));
> >>>> -
> >>>> - drm_crtc_vblank_put(&crtc->base);
> >>>> - }
> >>>> -}
> >>>> -
> >>>> -static bool needs_vblank_wait(struct intel_crtc_state *crtc_state)
> >>>> -{
> >>>> - /* fb updated, need to unpin old fb */
> >>>> - if (crtc_state->fb_changed)
> >>>> - return true;
> >>>> -
> >>>> - /* wm changes, need vblank before final wm's */
> >>>> - if (crtc_state->update_wm_post)
> >>>> - return true;
> >>>> -
> >>>> - if (crtc_state->wm.need_postvbl_update)
> >>>> - return true;
> >>>> -
> >>>> - return false;
> >>>> -}
> >>>> -
> >>>> static void intel_update_crtc(struct drm_crtc *crtc,
> >>>> struct drm_atomic_state *state,
> >>>> struct drm_crtc_state *old_crtc_state,
> >>>> - struct drm_crtc_state *new_crtc_state,
> >>>> - unsigned int *crtc_vblank_mask)
> >>>> + struct drm_crtc_state *new_crtc_state)
> >>>> {
> >>>> struct drm_device *dev = crtc->dev;
> >>>> struct drm_i915_private *dev_priv = to_i915(dev);
> >>>> @@ -12203,13 +12140,9 @@ static void intel_update_crtc(struct drm_crtc *crtc,
> >>>> }
> >>>>
> >>>> drm_atomic_helper_commit_planes_on_crtc(old_crtc_state);
> >>>> -
> >>>> - if (needs_vblank_wait(pipe_config))
> >>>> - *crtc_vblank_mask |= drm_crtc_mask(crtc);
> >>>> }
> >>>>
> >>>> -static void intel_update_crtcs(struct drm_atomic_state *state,
> >>>> - unsigned int *crtc_vblank_mask)
> >>>> +static void intel_update_crtcs(struct drm_atomic_state *state)
> >>>> {
> >>>> struct drm_crtc *crtc;
> >>>> struct drm_crtc_state *old_crtc_state, *new_crtc_state;
> >>>> @@ -12220,12 +12153,11 @@ static void intel_update_crtcs(struct drm_atomic_state *state,
> >>>> continue;
> >>>>
> >>>> intel_update_crtc(crtc, state, old_crtc_state,
> >>>> - new_crtc_state, crtc_vblank_mask);
> >>>> + new_crtc_state);
> >>>> }
> >>>> }
> >>>>
> >>>> -static void skl_update_crtcs(struct drm_atomic_state *state,
> >>>> - unsigned int *crtc_vblank_mask)
> >>>> +static void skl_update_crtcs(struct drm_atomic_state *state)
> >>>> {
> >>>> struct drm_i915_private *dev_priv = to_i915(state->dev);
> >>>> struct intel_atomic_state *intel_state = to_intel_atomic_state(state);
> >>>> @@ -12284,7 +12216,7 @@ static void skl_update_crtcs(struct drm_atomic_state *state,
> >>>> vbl_wait = true;
> >>>>
> >>>> intel_update_crtc(crtc, state, old_crtc_state,
> >>>> - new_crtc_state, crtc_vblank_mask);
> >>>> + new_crtc_state);
> >>>>
> >>>> if (vbl_wait)
> >>>> intel_wait_for_vblank(dev_priv, pipe);
> >>>> @@ -12346,7 +12278,6 @@ static void intel_atomic_commit_tail(struct drm_atomic_state *state)
> >>>> struct intel_crtc_state *intel_cstate;
> >>>> bool hw_check = intel_state->modeset;
> >>>> u64 put_domains[I915_MAX_PIPES] = {};
> >>>> - unsigned crtc_vblank_mask = 0;
> >>>> int i;
> >>>>
> >>>> intel_atomic_commit_fence_wait(intel_state);
> >>>> @@ -12438,7 +12369,7 @@ static void intel_atomic_commit_tail(struct drm_atomic_state *state)
> >>>> pm_qos_update_request(&dev_priv->pm_qos_atomic, 0);
> >>>>
> >>>> /* Now enable the clocks, plane, pipe, and connectors that we set up. */
> >>>> - dev_priv->display.update_crtcs(state, &crtc_vblank_mask);
> >>>> + dev_priv->display.update_crtcs(state);
> >>>>
> >>>> /* FIXME: We should call drm_atomic_helper_commit_hw_done() here
> >>>> * already, but still need the state for the delayed optimization. To
> >>>> @@ -12450,7 +12381,7 @@ static void intel_atomic_commit_tail(struct drm_atomic_state *state)
> >>>> * we don't need out special handling any more.
> >>>> */
> >>>> if (!state->legacy_cursor_update)
> >>> I think this if is dead code, since either we use the fastpath in
> >>> intel_legacy_cursor_update, which means no atomic commit. Or we don't, and
> >>> then we clear this hack (on most platforms at least) since it just wreaks
> >>> complete havoc.
> >>>
> >>> We should probably do this logic in the async helpers, i.e. if async
> >>> helpers reject a cursor update, clear state->legacy_cursor_update.
> >>>
> >>> Since I think we don't necessarily need this patch in this series, I think
> >>> it'd be better in a separate series to straighten out the async_update
> >>> story. Which would then include moving i915 over to the core support.
> >> Erm, not sure what you mean here, isn't state->legacy_cursor_update mostly false, which means in most cases we'll wait?
> > Yup. And the few cases where it's true should be handled by the
> > fastpath/async plane update logic. Would allow us to ditch a few
> > conditions all over the code.
> > -Daniel
>
> I've done some more tests, and it seems this patch is required.
>
> Without this we may not always wait, and that could result in spurious failures of page flip with -EBUSY.
> I'd love to hide this from userspace, but I don't think that's possible yet. It's best to always call
> drm_atomic_helper_wait_for_flip_done() for now. It's a noop for legacy_cursor_update anyway.
> commit->flip_done is always set early.

I think we have a mistunderstanding here, I meant to say that you should
imo remove the if (state->legacy_cursor_update) check and call the
wait_for_flips_done helper unconditionally, not remove the call to the
function itself. That should work, and since we have a separate cursor
fastpath, also not cause troubles.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation