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

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Op 04-09-17 om 09:30 schreef Daniel Vetter:
> 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.
True. The if is even a noop because setup_commit completes flip_done immediately..
Should be harmless to remove..

~Maarten
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