Re: [PATCH v2 15/24] drm/msm: dpu: Stop using encoder->crtc pointer

[Sean Paul <sean@poorly.run>]

On Mon, Nov 19, 2018 at 12:03:53PM -0800, Jeykumar Sankaran wrote:
> On 2018-11-16 13:14, Sean Paul wrote:
> > On Fri, Nov 16, 2018 at 12:05:09PM -0800, Jeykumar Sankaran wrote:
> > > On 2018-11-16 10:42, Sean Paul wrote:
> > > > From: Sean Paul <seanpaul@chromium.org>
> > > >
> > > > It's for legacy drivers, for atomic drivers crtc->state->encoder_mask
> > > > should be used to map encoder to crtc.
> > > >
> > > > Changes in v2:
> > > > - None
> > > >
> > > > Signed-off-by: Sean Paul <seanpaul@chromium.org>
> > > > ---
> > > >  drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c | 46
> > ++++++++----------------
> > > >  drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c  | 19 +++++++---
> > > >  2 files changed, 29 insertions(+), 36 deletions(-)
> > > >
> > > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > > > b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > > > index 156f4c77ca44..a008a87a8113 100644
> > > > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > > > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_crtc.c
> > > > @@ -284,9 +284,9 @@ enum dpu_intf_mode dpu_crtc_get_intf_mode(struct
> > > > drm_crtc *crtc)
> > > >  		return INTF_MODE_NONE;
> > > >  	}
> > > >
> > > > -	drm_for_each_encoder(encoder, crtc->dev)
> > > > -		if (encoder->crtc == crtc)
> > > > -			return dpu_encoder_get_intf_mode(encoder);
> > > > +	/* TODO: Returns the first INTF_MODE, could there be multiple
> > > > values? */
> > > > +	drm_for_each_encoder_mask(encoder, crtc->dev,
> > > > crtc->state->encoder_mask)
> > > > +		return dpu_encoder_get_intf_mode(encoder);
> > > >
> > > >  	return INTF_MODE_NONE;
> > > >  }
> > > > @@ -551,13 +551,9 @@ static void dpu_crtc_atomic_begin(struct drm_crtc
> > > > *crtc,
> > > >  		spin_unlock_irqrestore(&dev->event_lock, flags);
> > > >  	}
> > > >
> > > > -	list_for_each_entry(encoder, &dev->mode_config.encoder_list, head)
> > > > {
> > > > -		if (encoder->crtc != crtc)
> > > > -			continue;
> > > > -
> > > > -		/* encoder will trigger pending mask now */
> > > > +	/* encoder will trigger pending mask now */
> > > > +	drm_for_each_encoder_mask(encoder, crtc->dev,
> > > > crtc->state->encoder_mask)
> > > >  		dpu_encoder_trigger_kickoff_pending(encoder);
> > > > -	}
> > > >
> > > >  	/*
> > > >  	 * If no mixers have been allocated in dpu_crtc_atomic_check(),
> > > > @@ -704,7 +700,6 @@ static int _dpu_crtc_wait_for_frame_done(struct
> > > > drm_crtc *crtc)
> > > >  void dpu_crtc_commit_kickoff(struct drm_crtc *crtc)
> > > >  {
> > > >  	struct drm_encoder *encoder;
> > > > -	struct drm_device *dev = crtc->dev;
> > > >  	struct dpu_crtc *dpu_crtc = to_dpu_crtc(crtc);
> > > >  	struct dpu_kms *dpu_kms = _dpu_crtc_get_kms(crtc);
> > > >  	struct dpu_crtc_state *cstate = to_dpu_crtc_state(crtc->state);
> > > > @@ -720,16 +715,13 @@ void dpu_crtc_commit_kickoff(struct drm_crtc
> > > > *crtc)
> > > >
> > > >  	DPU_ATRACE_BEGIN("crtc_commit");
> > > >
> > > > -	list_for_each_entry(encoder, &dev->mode_config.encoder_list, head)
> > > > {
> > > > +	/*
> > > > +	 * Encoder will flush/start now, unless it has a tx pending. If
> > > > so, it
> > > > +	 * may delay and flush at an irq event (e.g. ppdone)
> > > > +	 */
> > > > +	drm_for_each_encoder_mask(encoder, crtc->dev,
> > > > +				  crtc->state->encoder_mask) {
> > > >  		struct dpu_encoder_kickoff_params params = { 0 };
> > > > -
> > > > -		if (encoder->crtc != crtc)
> > > > -			continue;
> > > > -
> > > > -		/*
> > > > -		 * Encoder will flush/start now, unless it has a tx
> > > > pending.
> > > > -		 * If so, it may delay and flush at an irq event (e.g.
> > > > ppdone)
> > > > -		 */
> > > >  		dpu_encoder_prepare_for_kickoff(encoder, &params);
> > > >  	}
> > > >
> > > > @@ -754,12 +746,8 @@ void dpu_crtc_commit_kickoff(struct drm_crtc
> > *crtc)
> > > >
> > > >  	dpu_vbif_clear_errors(dpu_kms);
> > > >
> > > > -	list_for_each_entry(encoder, &dev->mode_config.encoder_list, head)
> > > > {
> > > > -		if (encoder->crtc != crtc)
> > > > -			continue;
> > > > -
> > > > +	drm_for_each_encoder_mask(encoder, crtc->dev,
> > > > crtc->state->encoder_mask)
> > > >  		dpu_encoder_kickoff(encoder);
> > > > -	}
> > > We wont be holding the modeset locks here (and in crtc_atomic_begin)
> > > in
> > the
> > > display thread. Is
> > > it safe to iterate over encoder_mask?
> > 
> > Hmm, I'm not sure I follow. AFAICT, there are 2 callsites for
> > dpu_crtc_commit_kickoff():
> > 
> > 1- dpu_kms_encoder_enable() which is called via the
> > encoder->funcs->enable
> > hook
> > 2- dpu_kms_commit() which is called in the
> > mode_config->funcs->atomic_commit_tail
> 
> atomic_commit_tail will be called from the WQ. Do we hold
> the modeset locks in the WQ? I believe userspace thread will drop
> the locks at the end of drm_mode_atomic_ioctl.

Accessing state is safe in non-blocking commits due to stalling any subsequent
commits until the previous one has completed. Check out the comment at:

https://cgit.freedesktop.org/drm-tip/tree/drivers/gpu/drm/drm_atomic_helper.c#n1754

Sean

> 
> Thanks
> > 
> > Both of these callsites will hold the modeset locks.
> > 
> > Am I missing something?
> > 
> > Thanks for your review,
> > 
> > Sean
> > 
> > > >
> > > >  end:
> > > >  	reinit_completion(&dpu_crtc->frame_done_comp);
> > > > @@ -883,11 +871,8 @@ static void dpu_crtc_disable(struct drm_crtc
> > *crtc)
> > > >
> > > >  	dpu_core_perf_crtc_update(crtc, 0, true);
> > > >
> > > > -	drm_for_each_encoder(encoder, crtc->dev) {
> > > > -		if (encoder->crtc != crtc)
> > > > -			continue;
> > > > +	drm_for_each_encoder_mask(encoder, crtc->dev,
> > > > crtc->state->encoder_mask)
> > > >  		dpu_encoder_register_frame_event_callback(encoder, NULL,
> > > > NULL);
> > > > -	}
> > > >
> > > >  	memset(cstate->mixers, 0, sizeof(cstate->mixers));
> > > >  	cstate->num_mixers = 0;
> > > > @@ -922,12 +907,9 @@ static void dpu_crtc_enable(struct drm_crtc
> > *crtc,
> > > >  	DRM_DEBUG_KMS("crtc%d\n", crtc->base.id);
> > > >  	dpu_crtc = to_dpu_crtc(crtc);
> > > >
> > > > -	drm_for_each_encoder(encoder, crtc->dev) {
> > > > -		if (encoder->crtc != crtc)
> > > > -			continue;
> > > > +	drm_for_each_encoder_mask(encoder, crtc->dev,
> > > > crtc->state->encoder_mask)
> > > >  		dpu_encoder_register_frame_event_callback(encoder,
> > > >  				dpu_crtc_frame_event_cb, (void *)crtc);
> > > > -	}
> > > >
> > > >  	mutex_lock(&dpu_crtc->crtc_lock);
> > > >  	trace_dpu_crtc_enable(DRMID(crtc), true, dpu_crtc);
> > > > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> > > > b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> > > > index 1bec4540f3e1..64134d619748 100644
> > > > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> > > > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_kms.c
> > > > @@ -320,7 +320,10 @@ static void dpu_kms_prepare_commit(struct msm_kms
> > > > *kms,
> > > >  	struct dpu_kms *dpu_kms;
> > > >  	struct msm_drm_private *priv;
> > > >  	struct drm_device *dev;
> > > > +	struct drm_crtc *crtc;
> > > > +	struct drm_crtc_state *crtc_state;
> > > >  	struct drm_encoder *encoder;
> > > > +	int i;
> > > >
> > > >  	if (!kms)
> > > >  		return;
> > > > @@ -332,9 +335,13 @@ static void dpu_kms_prepare_commit(struct msm_kms
> > > > *kms,
> > > >  	priv = dev->dev_private;
> > > >  	pm_runtime_get_sync(&dpu_kms->pdev->dev);
> > > >
> > > > -	list_for_each_entry(encoder, &dev->mode_config.encoder_list, head)
> > > > -		if (encoder->crtc != NULL)
> > > > +	/* Call prepare_commit for all affected encoders */
> > > > +	for_each_new_crtc_in_state(state, crtc, crtc_state, i) {
> > > > +		drm_for_each_encoder_mask(encoder, crtc->dev,
> > > > +					  crtc_state->encoder_mask) {
> > > >  			dpu_encoder_prepare_commit(encoder);
> > > > +		}
> > > > +	}
> > > >  }
> > > >
> > > >  /*
> > > > @@ -344,13 +351,17 @@ static void dpu_kms_prepare_commit(struct
> > msm_kms
> > > > *kms,
> > > >  void dpu_kms_encoder_enable(struct drm_encoder *encoder)
> > > >  {
> > > >  	const struct drm_encoder_helper_funcs *funcs =
> > > > encoder->helper_private;
> > > > -	struct drm_crtc *crtc = encoder->crtc;
> > > > +	struct drm_device *dev = encoder->dev;
> > > > +	struct drm_crtc *crtc;
> > > >
> > > >  	/* Forward this enable call to the commit hook */
> > > >  	if (funcs && funcs->commit)
> > > >  		funcs->commit(encoder);
> > > >
> > > > -	if (crtc && crtc->state->active) {
> > > > +	drm_for_each_crtc(crtc, dev) {
> > > > +		if (!(crtc->state->encoder_mask &
> > > > drm_encoder_mask(encoder)))
> > > > +			continue;
> > > > +
> > > >  		trace_dpu_kms_enc_enable(DRMID(crtc));
> > > >  		dpu_crtc_commit_kickoff(crtc);
> > > >  	}
> > > 
> > > --
> > > Jeykumar S
> 
> -- 
> Jeykumar S

-- 
Sean Paul, Software Engineer, Google / Chromium OS
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