[PATCH 1/2] drm/msm/dpu: move vblank events to complete_commit()

[PATCH 1/2] drm/msm/dpu: move vblank events to complete_commit()

[Rob Clark]

From: Rob Clark <robdclark@chromium.org>

We could get a vblank event racing with the current atomic commit,
resulting in sending the pageflip event to userspace early, causing
tearing.  On the other hand, complete_commit() ensures that the
pending flush is complete.

Signed-off-by: Rob Clark <robdclark@chromium.org>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
index c2729f71e2fa..89c0245b5de5 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
@@ -297,7 +297,6 @@ void dpu_crtc_vblank_callback(struct drm_crtc *crtc)
 		dpu_crtc->vblank_cb_time = ktime_get();
 	else
 		dpu_crtc->vblank_cb_count++;
-	_dpu_crtc_complete_flip(crtc);
 	drm_crtc_handle_vblank(crtc);
 	trace_dpu_crtc_vblank_cb(DRMID(crtc));
 }
@@ -402,6 +401,7 @@ static void dpu_crtc_frame_event_cb(void *data, u32 event)
 void dpu_crtc_complete_commit(struct drm_crtc *crtc)
 {
 	trace_dpu_crtc_complete_commit(DRMID(crtc));
+	_dpu_crtc_complete_flip(crtc);
 }
 
 static void _dpu_crtc_setup_lm_bounds(struct drm_crtc *crtc,
-- 
2.26.2

[PATCH 2/2] drm/msm/dpu: clean up some impossibilities

[Rob Clark]

From: Rob Clark <robdclark@chromium.org>

Signed-off-by: Rob Clark <robdclark@chromium.org>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 81 ++++--------------------
 1 file changed, 12 insertions(+), 69 deletions(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
index 89c0245b5de5..ad49b0e17fcb 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
@@ -265,11 +265,6 @@ enum dpu_intf_mode dpu_crtc_get_intf_mode(struct drm_crtc *crtc)
 {
 	struct drm_encoder *encoder;
 
-	if (!crtc) {
-		DPU_ERROR("invalid crtc\n");
-		return INTF_MODE_NONE;
-	}
-
 	/*
 	 * TODO: This function is called from dpu debugfs and as part of atomic
 	 * check. When called from debugfs, the crtc->mutex must be held to
@@ -500,12 +495,6 @@ static void dpu_crtc_atomic_begin(struct drm_crtc *crtc,
 	struct dpu_crtc_state *cstate;
 	struct drm_encoder *encoder;
 	struct drm_device *dev;
-	unsigned long flags;
-
-	if (!crtc) {
-		DPU_ERROR("invalid crtc\n");
-		return;
-	}
 
 	if (!crtc->state->enable) {
 		DPU_DEBUG("crtc%d -> enable %d, skip atomic_begin\n",
@@ -521,15 +510,6 @@ static void dpu_crtc_atomic_begin(struct drm_crtc *crtc,
 
 	_dpu_crtc_setup_lm_bounds(crtc, crtc->state);
 
-	if (dpu_crtc->event) {
-		WARN_ON(dpu_crtc->event);
-	} else {
-		spin_lock_irqsave(&dev->event_lock, flags);
-		dpu_crtc->event = crtc->state->event;
-		crtc->state->event = NULL;
-		spin_unlock_irqrestore(&dev->event_lock, flags);
-	}
-
 	/* encoder will trigger pending mask now */
 	drm_for_each_encoder_mask(encoder, crtc->dev, crtc->state->encoder_mask)
 		dpu_encoder_trigger_kickoff_pending(encoder);
@@ -583,14 +563,11 @@ static void dpu_crtc_atomic_flush(struct drm_crtc *crtc,
 		return;
 	}
 
-	if (dpu_crtc->event) {
-		DPU_DEBUG("already received dpu_crtc->event\n");
-	} else {
-		spin_lock_irqsave(&dev->event_lock, flags);
-		dpu_crtc->event = crtc->state->event;
-		crtc->state->event = NULL;
-		spin_unlock_irqrestore(&dev->event_lock, flags);
-	}
+	WARN_ON(dpu_crtc->event);
+	spin_lock_irqsave(&dev->event_lock, flags);
+	dpu_crtc->event = crtc->state->event;
+	crtc->state->event = NULL;
+	spin_unlock_irqrestore(&dev->event_lock, flags);
 
 	/*
 	 * If no mixers has been allocated in dpu_crtc_atomic_check(),
@@ -635,14 +612,7 @@ static void dpu_crtc_atomic_flush(struct drm_crtc *crtc,
 static void dpu_crtc_destroy_state(struct drm_crtc *crtc,
 		struct drm_crtc_state *state)
 {
-	struct dpu_crtc_state *cstate;
-
-	if (!crtc || !state) {
-		DPU_ERROR("invalid argument(s)\n");
-		return;
-	}
-
-	cstate = to_dpu_crtc_state(state);
+	struct dpu_crtc_state *cstate = to_dpu_crtc_state(state);
 
 	DPU_DEBUG("crtc%d\n", crtc->base.id);
 
@@ -731,14 +701,8 @@ static void dpu_crtc_reset(struct drm_crtc *crtc)
  */
 static struct drm_crtc_state *dpu_crtc_duplicate_state(struct drm_crtc *crtc)
 {
-	struct dpu_crtc_state *cstate, *old_cstate;
-
-	if (!crtc || !crtc->state) {
-		DPU_ERROR("invalid argument(s)\n");
-		return NULL;
-	}
+	struct dpu_crtc_state *cstate, *old_cstate = to_dpu_crtc_state(crtc->state);
 
-	old_cstate = to_dpu_crtc_state(crtc->state);
 	cstate = kmemdup(old_cstate, sizeof(*old_cstate), GFP_KERNEL);
 	if (!cstate) {
 		DPU_ERROR("failed to allocate state\n");
@@ -754,19 +718,12 @@ static struct drm_crtc_state *dpu_crtc_duplicate_state(struct drm_crtc *crtc)
 static void dpu_crtc_disable(struct drm_crtc *crtc,
 			     struct drm_crtc_state *old_crtc_state)
 {
-	struct dpu_crtc *dpu_crtc;
-	struct dpu_crtc_state *cstate;
+	struct dpu_crtc *dpu_crtc = to_dpu_crtc(crtc);
+	struct dpu_crtc_state *cstate = to_dpu_crtc_state(crtc->state);
 	struct drm_encoder *encoder;
 	unsigned long flags;
 	bool release_bandwidth = false;
 
-	if (!crtc || !crtc->state) {
-		DPU_ERROR("invalid crtc\n");
-		return;
-	}
-	dpu_crtc = to_dpu_crtc(crtc);
-	cstate = to_dpu_crtc_state(crtc->state);
-
 	DRM_DEBUG_KMS("crtc%d\n", crtc->base.id);
 
 	/* Disable/save vblank irq handling */
@@ -825,19 +782,13 @@ static void dpu_crtc_disable(struct drm_crtc *crtc,
 static void dpu_crtc_enable(struct drm_crtc *crtc,
 		struct drm_crtc_state *old_crtc_state)
 {
-	struct dpu_crtc *dpu_crtc;
+	struct dpu_crtc *dpu_crtc = to_dpu_crtc(crtc);
 	struct drm_encoder *encoder;
 	bool request_bandwidth = false;
 
-	if (!crtc) {
-		DPU_ERROR("invalid crtc\n");
-		return;
-	}
-
 	pm_runtime_get_sync(crtc->dev->dev);
 
 	DRM_DEBUG_KMS("crtc%d\n", crtc->base.id);
-	dpu_crtc = to_dpu_crtc(crtc);
 
 	drm_for_each_encoder_mask(encoder, crtc->dev, crtc->state->encoder_mask) {
 		/* in video mode, we hold an extra bandwidth reference
@@ -873,9 +824,9 @@ struct plane_state {
 static int dpu_crtc_atomic_check(struct drm_crtc *crtc,
 		struct drm_crtc_state *state)
 {
-	struct dpu_crtc *dpu_crtc;
+	struct dpu_crtc *dpu_crtc = to_dpu_crtc(crtc);
+	struct dpu_crtc_state *cstate = to_dpu_crtc_state(state);
 	struct plane_state *pstates;
-	struct dpu_crtc_state *cstate;
 
 	const struct drm_plane_state *pstate;
 	struct drm_plane *plane;
@@ -889,16 +840,8 @@ static int dpu_crtc_atomic_check(struct drm_crtc *crtc,
 	int left_zpos_cnt = 0, right_zpos_cnt = 0;
 	struct drm_rect crtc_rect = { 0 };
 
-	if (!crtc) {
-		DPU_ERROR("invalid crtc\n");
-		return -EINVAL;
-	}
-
 	pstates = kzalloc(sizeof(*pstates) * DPU_STAGE_MAX * 4, GFP_KERNEL);
 
-	dpu_crtc = to_dpu_crtc(crtc);
-	cstate = to_dpu_crtc_state(state);
-
 	if (!state->enable || !state->active) {
 		DPU_DEBUG("crtc%d -> enable %d, active %d, skip atomic_check\n",
 				crtc->base.id, state->enable, state->active);
-- 
2.26.2

Re: [PATCH 1/2] drm/msm/dpu: move vblank events to complete_commit()

[abhinavk]

On 2020-09-07 10:04, Rob Clark wrote:
> From: Rob Clark <robdclark@chromium.org>
> 
> We could get a vblank event racing with the current atomic commit,
> resulting in sending the pageflip event to userspace early, causing
> tearing.  On the other hand, complete_commit() ensures that the
> pending flush is complete.
> 
> Signed-off-by: Rob Clark <robdclark@chromium.org>

I checked our downstream code as well and yes we are not signaling
page flips inside the vblank_cb and are doing it after 
wait_for_commit_done
This aligns with that.
Hence,
Reviewed-by: Abhinav Kumar <abhinavk@codeaurora.org>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> index c2729f71e2fa..89c0245b5de5 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> @@ -297,7 +297,6 @@ void dpu_crtc_vblank_callback(struct drm_crtc 
> *crtc)
>  		dpu_crtc->vblank_cb_time = ktime_get();
>  	else
>  		dpu_crtc->vblank_cb_count++;
> -	_dpu_crtc_complete_flip(crtc);
>  	drm_crtc_handle_vblank(crtc);
>  	trace_dpu_crtc_vblank_cb(DRMID(crtc));
>  }
> @@ -402,6 +401,7 @@ static void dpu_crtc_frame_event_cb(void *data, u32 
> event)
>  void dpu_crtc_complete_commit(struct drm_crtc *crtc)
>  {
>  	trace_dpu_crtc_complete_commit(DRMID(crtc));
> +	_dpu_crtc_complete_flip(crtc);
>  }
> 
>  static void _dpu_crtc_setup_lm_bounds(struct drm_crtc *crtc,

Re: [PATCH 2/2] drm/msm/dpu: clean up some impossibilities

[abhinavk]

On 2020-09-07 10:04, Rob Clark wrote:
> From: Rob Clark <robdclark@chromium.org>
> 
> Signed-off-by: Rob Clark <robdclark@chromium.org>
> ---
>  drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 81 ++++--------------------
>  1 file changed, 12 insertions(+), 69 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> index 89c0245b5de5..ad49b0e17fcb 100644
> --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> @@ -265,11 +265,6 @@ enum dpu_intf_mode dpu_crtc_get_intf_mode(struct
> drm_crtc *crtc)
>  {
>  	struct drm_encoder *encoder;
> 
> -	if (!crtc) {
> -		DPU_ERROR("invalid crtc\n");
> -		return INTF_MODE_NONE;
> -	}
> -
>  	/*
>  	 * TODO: This function is called from dpu debugfs and as part of 
> atomic
>  	 * check. When called from debugfs, the crtc->mutex must be held to
> @@ -500,12 +495,6 @@ static void dpu_crtc_atomic_begin(struct drm_crtc 
> *crtc,
>  	struct dpu_crtc_state *cstate;
>  	struct drm_encoder *encoder;
>  	struct drm_device *dev;
> -	unsigned long flags;
> -
> -	if (!crtc) {
> -		DPU_ERROR("invalid crtc\n");
> -		return;
> -	}
> 
>  	if (!crtc->state->enable) {
>  		DPU_DEBUG("crtc%d -> enable %d, skip atomic_begin\n",
> @@ -521,15 +510,6 @@ static void dpu_crtc_atomic_begin(struct drm_crtc 
> *crtc,
> 
>  	_dpu_crtc_setup_lm_bounds(crtc, crtc->state);
> 
> -	if (dpu_crtc->event) {
> -		WARN_ON(dpu_crtc->event);
> -	} else {
> -		spin_lock_irqsave(&dev->event_lock, flags);
> -		dpu_crtc->event = crtc->state->event;
> -		crtc->state->event = NULL;
> -		spin_unlock_irqrestore(&dev->event_lock, flags);
> -	}
> -
>  	/* encoder will trigger pending mask now */
>  	drm_for_each_encoder_mask(encoder, crtc->dev, 
> crtc->state->encoder_mask)
>  		dpu_encoder_trigger_kickoff_pending(encoder);
> @@ -583,14 +563,11 @@ static void dpu_crtc_atomic_flush(struct drm_crtc 
> *crtc,
>  		return;
>  	}
> 
> -	if (dpu_crtc->event) {
> -		DPU_DEBUG("already received dpu_crtc->event\n");
> -	} else {
> -		spin_lock_irqsave(&dev->event_lock, flags);
> -		dpu_crtc->event = crtc->state->event;
> -		crtc->state->event = NULL;
> -		spin_unlock_irqrestore(&dev->event_lock, flags);
> -	}
> +	WARN_ON(dpu_crtc->event);
before the patch "move vblank events to complete_commit()", the dpu_crtc 
events
were consumed in the _dpu_crtc_complete_flip(). So there was a chance 
that if the vblank event
did not come in time before the next commit, dpu_crtc->event will not be 
consumed.

But after the patch, _dpu_crtc_complete_flip() is being signaled in 
dpu_crtc_complete_commit()
which will always happen, so is there any case where we will hit this 
warning at all or will this
catch some other condition?

> +	spin_lock_irqsave(&dev->event_lock, flags);
> +	dpu_crtc->event = crtc->state->event;
> +	crtc->state->event = NULL;
> +	spin_unlock_irqrestore(&dev->event_lock, flags);
> 
>  	/*
>  	 * If no mixers has been allocated in dpu_crtc_atomic_check(),
> @@ -635,14 +612,7 @@ static void dpu_crtc_atomic_flush(struct drm_crtc 
> *crtc,
>  static void dpu_crtc_destroy_state(struct drm_crtc *crtc,
>  		struct drm_crtc_state *state)
>  {
> -	struct dpu_crtc_state *cstate;
> -
> -	if (!crtc || !state) {
> -		DPU_ERROR("invalid argument(s)\n");
> -		return;
> -	}
> -
> -	cstate = to_dpu_crtc_state(state);
> +	struct dpu_crtc_state *cstate = to_dpu_crtc_state(state);
> 
>  	DPU_DEBUG("crtc%d\n", crtc->base.id);
> 
> @@ -731,14 +701,8 @@ static void dpu_crtc_reset(struct drm_crtc *crtc)
>   */
>  static struct drm_crtc_state *dpu_crtc_duplicate_state(struct drm_crtc 
> *crtc)
>  {
> -	struct dpu_crtc_state *cstate, *old_cstate;
> -
> -	if (!crtc || !crtc->state) {
> -		DPU_ERROR("invalid argument(s)\n");
> -		return NULL;
> -	}
> +	struct dpu_crtc_state *cstate, *old_cstate = 
> to_dpu_crtc_state(crtc->state);
> 
> -	old_cstate = to_dpu_crtc_state(crtc->state);
>  	cstate = kmemdup(old_cstate, sizeof(*old_cstate), GFP_KERNEL);
>  	if (!cstate) {
>  		DPU_ERROR("failed to allocate state\n");
> @@ -754,19 +718,12 @@ static struct drm_crtc_state
> *dpu_crtc_duplicate_state(struct drm_crtc *crtc)
>  static void dpu_crtc_disable(struct drm_crtc *crtc,
>  			     struct drm_crtc_state *old_crtc_state)
>  {
> -	struct dpu_crtc *dpu_crtc;
> -	struct dpu_crtc_state *cstate;
> +	struct dpu_crtc *dpu_crtc = to_dpu_crtc(crtc);
> +	struct dpu_crtc_state *cstate = to_dpu_crtc_state(crtc->state);
>  	struct drm_encoder *encoder;
>  	unsigned long flags;
>  	bool release_bandwidth = false;
> 
> -	if (!crtc || !crtc->state) {
> -		DPU_ERROR("invalid crtc\n");
> -		return;
> -	}
> -	dpu_crtc = to_dpu_crtc(crtc);
> -	cstate = to_dpu_crtc_state(crtc->state);
> -
>  	DRM_DEBUG_KMS("crtc%d\n", crtc->base.id);
> 
>  	/* Disable/save vblank irq handling */
> @@ -825,19 +782,13 @@ static void dpu_crtc_disable(struct drm_crtc 
> *crtc,
>  static void dpu_crtc_enable(struct drm_crtc *crtc,
>  		struct drm_crtc_state *old_crtc_state)
>  {
> -	struct dpu_crtc *dpu_crtc;
> +	struct dpu_crtc *dpu_crtc = to_dpu_crtc(crtc);
>  	struct drm_encoder *encoder;
>  	bool request_bandwidth = false;
> 
> -	if (!crtc) {
> -		DPU_ERROR("invalid crtc\n");
> -		return;
> -	}
> -
>  	pm_runtime_get_sync(crtc->dev->dev);
> 
>  	DRM_DEBUG_KMS("crtc%d\n", crtc->base.id);
> -	dpu_crtc = to_dpu_crtc(crtc);
> 
>  	drm_for_each_encoder_mask(encoder, crtc->dev, 
> crtc->state->encoder_mask) {
>  		/* in video mode, we hold an extra bandwidth reference
> @@ -873,9 +824,9 @@ struct plane_state {
>  static int dpu_crtc_atomic_check(struct drm_crtc *crtc,
>  		struct drm_crtc_state *state)
>  {
> -	struct dpu_crtc *dpu_crtc;
> +	struct dpu_crtc *dpu_crtc = to_dpu_crtc(crtc);
> +	struct dpu_crtc_state *cstate = to_dpu_crtc_state(state);
>  	struct plane_state *pstates;
> -	struct dpu_crtc_state *cstate;
> 
>  	const struct drm_plane_state *pstate;
>  	struct drm_plane *plane;
> @@ -889,16 +840,8 @@ static int dpu_crtc_atomic_check(struct drm_crtc 
> *crtc,
>  	int left_zpos_cnt = 0, right_zpos_cnt = 0;
>  	struct drm_rect crtc_rect = { 0 };
> 
> -	if (!crtc) {
> -		DPU_ERROR("invalid crtc\n");
> -		return -EINVAL;
> -	}
> -
>  	pstates = kzalloc(sizeof(*pstates) * DPU_STAGE_MAX * 4, GFP_KERNEL);
> 
> -	dpu_crtc = to_dpu_crtc(crtc);
> -	cstate = to_dpu_crtc_state(state);
> -
>  	if (!state->enable || !state->active) {
>  		DPU_DEBUG("crtc%d -> enable %d, active %d, skip atomic_check\n",
>  				crtc->base.id, state->enable, state->active);

Re: [PATCH 2/2] drm/msm/dpu: clean up some impossibilities

[Rob Clark]

On Tue, Sep 8, 2020 at 12:44 PM <abhinavk@codeaurora.org> wrote:
>
> On 2020-09-07 10:04, Rob Clark wrote:
> > From: Rob Clark <robdclark@chromium.org>
> >
> > Signed-off-by: Rob Clark <robdclark@chromium.org>
> > ---
> >  drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 81 ++++--------------------
> >  1 file changed, 12 insertions(+), 69 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > index 89c0245b5de5..ad49b0e17fcb 100644
> > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > @@ -265,11 +265,6 @@ enum dpu_intf_mode dpu_crtc_get_intf_mode(struct
> > drm_crtc *crtc)
> >  {
> >       struct drm_encoder *encoder;
> >
> > -     if (!crtc) {
> > -             DPU_ERROR("invalid crtc\n");
> > -             return INTF_MODE_NONE;
> > -     }
> > -
> >       /*
> >        * TODO: This function is called from dpu debugfs and as part of
> > atomic
> >        * check. When called from debugfs, the crtc->mutex must be held to
> > @@ -500,12 +495,6 @@ static void dpu_crtc_atomic_begin(struct drm_crtc
> > *crtc,
> >       struct dpu_crtc_state *cstate;
> >       struct drm_encoder *encoder;
> >       struct drm_device *dev;
> > -     unsigned long flags;
> > -
> > -     if (!crtc) {
> > -             DPU_ERROR("invalid crtc\n");
> > -             return;
> > -     }
> >
> >       if (!crtc->state->enable) {
> >               DPU_DEBUG("crtc%d -> enable %d, skip atomic_begin\n",
> > @@ -521,15 +510,6 @@ static void dpu_crtc_atomic_begin(struct drm_crtc
> > *crtc,
> >
> >       _dpu_crtc_setup_lm_bounds(crtc, crtc->state);
> >
> > -     if (dpu_crtc->event) {
> > -             WARN_ON(dpu_crtc->event);
> > -     } else {
> > -             spin_lock_irqsave(&dev->event_lock, flags);
> > -             dpu_crtc->event = crtc->state->event;
> > -             crtc->state->event = NULL;
> > -             spin_unlock_irqrestore(&dev->event_lock, flags);
> > -     }
> > -
> >       /* encoder will trigger pending mask now */
> >       drm_for_each_encoder_mask(encoder, crtc->dev,
> > crtc->state->encoder_mask)
> >               dpu_encoder_trigger_kickoff_pending(encoder);
> > @@ -583,14 +563,11 @@ static void dpu_crtc_atomic_flush(struct drm_crtc
> > *crtc,
> >               return;
> >       }
> >
> > -     if (dpu_crtc->event) {
> > -             DPU_DEBUG("already received dpu_crtc->event\n");
> > -     } else {
> > -             spin_lock_irqsave(&dev->event_lock, flags);
> > -             dpu_crtc->event = crtc->state->event;
> > -             crtc->state->event = NULL;
> > -             spin_unlock_irqrestore(&dev->event_lock, flags);
> > -     }
> > +     WARN_ON(dpu_crtc->event);
> before the patch "move vblank events to complete_commit()", the dpu_crtc
> events
> were consumed in the _dpu_crtc_complete_flip(). So there was a chance
> that if the vblank event
> did not come in time before the next commit, dpu_crtc->event will not be
> consumed.
>
> But after the patch, _dpu_crtc_complete_flip() is being signaled in
> dpu_crtc_complete_commit()
> which will always happen, so is there any case where we will hit this
> warning at all or will this
> catch some other condition?

The core drm-atomic bits will reject an incoming atomic update if the
previous one has not completed, so other than a coding bug, this
WARN_ON() should not be hit..  it's only purpose is to make it very
obvious if someone breaks something :-)

BR,
-R

>
> > +     spin_lock_irqsave(&dev->event_lock, flags);
> > +     dpu_crtc->event = crtc->state->event;
> > +     crtc->state->event = NULL;
> > +     spin_unlock_irqrestore(&dev->event_lock, flags);
> >
> >       /*
> >        * If no mixers has been allocated in dpu_crtc_atomic_check(),
> > @@ -635,14 +612,7 @@ static void dpu_crtc_atomic_flush(struct drm_crtc
> > *crtc,
> >  static void dpu_crtc_destroy_state(struct drm_crtc *crtc,
> >               struct drm_crtc_state *state)
> >  {
> > -     struct dpu_crtc_state *cstate;
> > -
> > -     if (!crtc || !state) {
> > -             DPU_ERROR("invalid argument(s)\n");
> > -             return;
> > -     }
> > -
> > -     cstate = to_dpu_crtc_state(state);
> > +     struct dpu_crtc_state *cstate = to_dpu_crtc_state(state);
> >
> >       DPU_DEBUG("crtc%d\n", crtc->base.id);
> >
> > @@ -731,14 +701,8 @@ static void dpu_crtc_reset(struct drm_crtc *crtc)
> >   */
> >  static struct drm_crtc_state *dpu_crtc_duplicate_state(struct drm_crtc
> > *crtc)
> >  {
> > -     struct dpu_crtc_state *cstate, *old_cstate;
> > -
> > -     if (!crtc || !crtc->state) {
> > -             DPU_ERROR("invalid argument(s)\n");
> > -             return NULL;
> > -     }
> > +     struct dpu_crtc_state *cstate, *old_cstate =
> > to_dpu_crtc_state(crtc->state);
> >
> > -     old_cstate = to_dpu_crtc_state(crtc->state);
> >       cstate = kmemdup(old_cstate, sizeof(*old_cstate), GFP_KERNEL);
> >       if (!cstate) {
> >               DPU_ERROR("failed to allocate state\n");
> > @@ -754,19 +718,12 @@ static struct drm_crtc_state
> > *dpu_crtc_duplicate_state(struct drm_crtc *crtc)
> >  static void dpu_crtc_disable(struct drm_crtc *crtc,
> >                            struct drm_crtc_state *old_crtc_state)
> >  {
> > -     struct dpu_crtc *dpu_crtc;
> > -     struct dpu_crtc_state *cstate;
> > +     struct dpu_crtc *dpu_crtc = to_dpu_crtc(crtc);
> > +     struct dpu_crtc_state *cstate = to_dpu_crtc_state(crtc->state);
> >       struct drm_encoder *encoder;
> >       unsigned long flags;
> >       bool release_bandwidth = false;
> >
> > -     if (!crtc || !crtc->state) {
> > -             DPU_ERROR("invalid crtc\n");
> > -             return;
> > -     }
> > -     dpu_crtc = to_dpu_crtc(crtc);
> > -     cstate = to_dpu_crtc_state(crtc->state);
> > -
> >       DRM_DEBUG_KMS("crtc%d\n", crtc->base.id);
> >
> >       /* Disable/save vblank irq handling */
> > @@ -825,19 +782,13 @@ static void dpu_crtc_disable(struct drm_crtc
> > *crtc,
> >  static void dpu_crtc_enable(struct drm_crtc *crtc,
> >               struct drm_crtc_state *old_crtc_state)
> >  {
> > -     struct dpu_crtc *dpu_crtc;
> > +     struct dpu_crtc *dpu_crtc = to_dpu_crtc(crtc);
> >       struct drm_encoder *encoder;
> >       bool request_bandwidth = false;
> >
> > -     if (!crtc) {
> > -             DPU_ERROR("invalid crtc\n");
> > -             return;
> > -     }
> > -
> >       pm_runtime_get_sync(crtc->dev->dev);
> >
> >       DRM_DEBUG_KMS("crtc%d\n", crtc->base.id);
> > -     dpu_crtc = to_dpu_crtc(crtc);
> >
> >       drm_for_each_encoder_mask(encoder, crtc->dev,
> > crtc->state->encoder_mask) {
> >               /* in video mode, we hold an extra bandwidth reference
> > @@ -873,9 +824,9 @@ struct plane_state {
> >  static int dpu_crtc_atomic_check(struct drm_crtc *crtc,
> >               struct drm_crtc_state *state)
> >  {
> > -     struct dpu_crtc *dpu_crtc;
> > +     struct dpu_crtc *dpu_crtc = to_dpu_crtc(crtc);
> > +     struct dpu_crtc_state *cstate = to_dpu_crtc_state(state);
> >       struct plane_state *pstates;
> > -     struct dpu_crtc_state *cstate;
> >
> >       const struct drm_plane_state *pstate;
> >       struct drm_plane *plane;
> > @@ -889,16 +840,8 @@ static int dpu_crtc_atomic_check(struct drm_crtc
> > *crtc,
> >       int left_zpos_cnt = 0, right_zpos_cnt = 0;
> >       struct drm_rect crtc_rect = { 0 };
> >
> > -     if (!crtc) {
> > -             DPU_ERROR("invalid crtc\n");
> > -             return -EINVAL;
> > -     }
> > -
> >       pstates = kzalloc(sizeof(*pstates) * DPU_STAGE_MAX * 4, GFP_KERNEL);
> >
> > -     dpu_crtc = to_dpu_crtc(crtc);
> > -     cstate = to_dpu_crtc_state(state);
> > -
> >       if (!state->enable || !state->active) {
> >               DPU_DEBUG("crtc%d -> enable %d, active %d, skip atomic_check\n",
> >                               crtc->base.id, state->enable, state->active);

Re: [PATCH 2/2] drm/msm/dpu: clean up some impossibilities

[abhinavk]

On 2020-09-08 13:11, Rob Clark wrote:
> On Tue, Sep 8, 2020 at 12:44 PM <abhinavk@codeaurora.org> wrote:
>> 
>> On 2020-09-07 10:04, Rob Clark wrote:
>> > From: Rob Clark <robdclark@chromium.org>
>> >
>> > Signed-off-by: Rob Clark <robdclark@chromium.org>

Reviewed-by: Abhinav Kumar <abhinavk@codeaurora.org>

>> > ---
>> >  drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 81 ++++--------------------
>> >  1 file changed, 12 insertions(+), 69 deletions(-)
>> >
>> > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>> > b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>> > index 89c0245b5de5..ad49b0e17fcb 100644
>> > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>> > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
>> > @@ -265,11 +265,6 @@ enum dpu_intf_mode dpu_crtc_get_intf_mode(struct
>> > drm_crtc *crtc)
>> >  {
>> >       struct drm_encoder *encoder;
>> >
>> > -     if (!crtc) {
>> > -             DPU_ERROR("invalid crtc\n");
>> > -             return INTF_MODE_NONE;
>> > -     }
>> > -
>> >       /*
>> >        * TODO: This function is called from dpu debugfs and as part of
>> > atomic
>> >        * check. When called from debugfs, the crtc->mutex must be held to
>> > @@ -500,12 +495,6 @@ static void dpu_crtc_atomic_begin(struct drm_crtc
>> > *crtc,
>> >       struct dpu_crtc_state *cstate;
>> >       struct drm_encoder *encoder;
>> >       struct drm_device *dev;
>> > -     unsigned long flags;
>> > -
>> > -     if (!crtc) {
>> > -             DPU_ERROR("invalid crtc\n");
>> > -             return;
>> > -     }
>> >
>> >       if (!crtc->state->enable) {
>> >               DPU_DEBUG("crtc%d -> enable %d, skip atomic_begin\n",
>> > @@ -521,15 +510,6 @@ static void dpu_crtc_atomic_begin(struct drm_crtc
>> > *crtc,
>> >
>> >       _dpu_crtc_setup_lm_bounds(crtc, crtc->state);
>> >
>> > -     if (dpu_crtc->event) {
>> > -             WARN_ON(dpu_crtc->event);
>> > -     } else {
>> > -             spin_lock_irqsave(&dev->event_lock, flags);
>> > -             dpu_crtc->event = crtc->state->event;
>> > -             crtc->state->event = NULL;
>> > -             spin_unlock_irqrestore(&dev->event_lock, flags);
>> > -     }
>> > -
>> >       /* encoder will trigger pending mask now */
>> >       drm_for_each_encoder_mask(encoder, crtc->dev,
>> > crtc->state->encoder_mask)
>> >               dpu_encoder_trigger_kickoff_pending(encoder);
>> > @@ -583,14 +563,11 @@ static void dpu_crtc_atomic_flush(struct drm_crtc
>> > *crtc,
>> >               return;
>> >       }
>> >
>> > -     if (dpu_crtc->event) {
>> > -             DPU_DEBUG("already received dpu_crtc->event\n");
>> > -     } else {
>> > -             spin_lock_irqsave(&dev->event_lock, flags);
>> > -             dpu_crtc->event = crtc->state->event;
>> > -             crtc->state->event = NULL;
>> > -             spin_unlock_irqrestore(&dev->event_lock, flags);
>> > -     }
>> > +     WARN_ON(dpu_crtc->event);
>> before the patch "move vblank events to complete_commit()", the 
>> dpu_crtc
>> events
>> were consumed in the _dpu_crtc_complete_flip(). So there was a chance
>> that if the vblank event
>> did not come in time before the next commit, dpu_crtc->event will not 
>> be
>> consumed.
>> 
>> But after the patch, _dpu_crtc_complete_flip() is being signaled in
>> dpu_crtc_complete_commit()
>> which will always happen, so is there any case where we will hit this
>> warning at all or will this
>> catch some other condition?
> 
> The core drm-atomic bits will reject an incoming atomic update if the
> previous one has not completed, so other than a coding bug, this
> WARN_ON() should not be hit..  it's only purpose is to make it very
> obvious if someone breaks something :-)
> 
> BR,
> -R
> 
>> 
>> > +     spin_lock_irqsave(&dev->event_lock, flags);
>> > +     dpu_crtc->event = crtc->state->event;
>> > +     crtc->state->event = NULL;
>> > +     spin_unlock_irqrestore(&dev->event_lock, flags);
>> >
>> >       /*
>> >        * If no mixers has been allocated in dpu_crtc_atomic_check(),
>> > @@ -635,14 +612,7 @@ static void dpu_crtc_atomic_flush(struct drm_crtc
>> > *crtc,
>> >  static void dpu_crtc_destroy_state(struct drm_crtc *crtc,
>> >               struct drm_crtc_state *state)
>> >  {
>> > -     struct dpu_crtc_state *cstate;
>> > -
>> > -     if (!crtc || !state) {
>> > -             DPU_ERROR("invalid argument(s)\n");
>> > -             return;
>> > -     }
>> > -
>> > -     cstate = to_dpu_crtc_state(state);
>> > +     struct dpu_crtc_state *cstate = to_dpu_crtc_state(state);
>> >
>> >       DPU_DEBUG("crtc%d\n", crtc->base.id);
>> >
>> > @@ -731,14 +701,8 @@ static void dpu_crtc_reset(struct drm_crtc *crtc)
>> >   */
>> >  static struct drm_crtc_state *dpu_crtc_duplicate_state(struct drm_crtc
>> > *crtc)
>> >  {
>> > -     struct dpu_crtc_state *cstate, *old_cstate;
>> > -
>> > -     if (!crtc || !crtc->state) {
>> > -             DPU_ERROR("invalid argument(s)\n");
>> > -             return NULL;
>> > -     }
>> > +     struct dpu_crtc_state *cstate, *old_cstate =
>> > to_dpu_crtc_state(crtc->state);
>> >
>> > -     old_cstate = to_dpu_crtc_state(crtc->state);
>> >       cstate = kmemdup(old_cstate, sizeof(*old_cstate), GFP_KERNEL);
>> >       if (!cstate) {
>> >               DPU_ERROR("failed to allocate state\n");
>> > @@ -754,19 +718,12 @@ static struct drm_crtc_state
>> > *dpu_crtc_duplicate_state(struct drm_crtc *crtc)
>> >  static void dpu_crtc_disable(struct drm_crtc *crtc,
>> >                            struct drm_crtc_state *old_crtc_state)
>> >  {
>> > -     struct dpu_crtc *dpu_crtc;
>> > -     struct dpu_crtc_state *cstate;
>> > +     struct dpu_crtc *dpu_crtc = to_dpu_crtc(crtc);
>> > +     struct dpu_crtc_state *cstate = to_dpu_crtc_state(crtc->state);
>> >       struct drm_encoder *encoder;
>> >       unsigned long flags;
>> >       bool release_bandwidth = false;
>> >
>> > -     if (!crtc || !crtc->state) {
>> > -             DPU_ERROR("invalid crtc\n");
>> > -             return;
>> > -     }
>> > -     dpu_crtc = to_dpu_crtc(crtc);
>> > -     cstate = to_dpu_crtc_state(crtc->state);
>> > -
>> >       DRM_DEBUG_KMS("crtc%d\n", crtc->base.id);
>> >
>> >       /* Disable/save vblank irq handling */
>> > @@ -825,19 +782,13 @@ static void dpu_crtc_disable(struct drm_crtc
>> > *crtc,
>> >  static void dpu_crtc_enable(struct drm_crtc *crtc,
>> >               struct drm_crtc_state *old_crtc_state)
>> >  {
>> > -     struct dpu_crtc *dpu_crtc;
>> > +     struct dpu_crtc *dpu_crtc = to_dpu_crtc(crtc);
>> >       struct drm_encoder *encoder;
>> >       bool request_bandwidth = false;
>> >
>> > -     if (!crtc) {
>> > -             DPU_ERROR("invalid crtc\n");
>> > -             return;
>> > -     }
>> > -
>> >       pm_runtime_get_sync(crtc->dev->dev);
>> >
>> >       DRM_DEBUG_KMS("crtc%d\n", crtc->base.id);
>> > -     dpu_crtc = to_dpu_crtc(crtc);
>> >
>> >       drm_for_each_encoder_mask(encoder, crtc->dev,
>> > crtc->state->encoder_mask) {
>> >               /* in video mode, we hold an extra bandwidth reference
>> > @@ -873,9 +824,9 @@ struct plane_state {
>> >  static int dpu_crtc_atomic_check(struct drm_crtc *crtc,
>> >               struct drm_crtc_state *state)
>> >  {
>> > -     struct dpu_crtc *dpu_crtc;
>> > +     struct dpu_crtc *dpu_crtc = to_dpu_crtc(crtc);
>> > +     struct dpu_crtc_state *cstate = to_dpu_crtc_state(state);
>> >       struct plane_state *pstates;
>> > -     struct dpu_crtc_state *cstate;
>> >
>> >       const struct drm_plane_state *pstate;
>> >       struct drm_plane *plane;
>> > @@ -889,16 +840,8 @@ static int dpu_crtc_atomic_check(struct drm_crtc
>> > *crtc,
>> >       int left_zpos_cnt = 0, right_zpos_cnt = 0;
>> >       struct drm_rect crtc_rect = { 0 };
>> >
>> > -     if (!crtc) {
>> > -             DPU_ERROR("invalid crtc\n");
>> > -             return -EINVAL;
>> > -     }
>> > -
>> >       pstates = kzalloc(sizeof(*pstates) * DPU_STAGE_MAX * 4, GFP_KERNEL);
>> >
>> > -     dpu_crtc = to_dpu_crtc(crtc);
>> > -     cstate = to_dpu_crtc_state(state);
>> > -
>> >       if (!state->enable || !state->active) {
>> >               DPU_DEBUG("crtc%d -> enable %d, active %d, skip atomic_check\n",
>> >                               crtc->base.id, state->enable, state->active);
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