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

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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@xxxxxxxxxxxxxxx>
> >>>> ---
> >>>>  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
http://blog.ffwll.ch
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