Re: [PATCH 11/12] drm/msm: dpu: Add ->enabled to dpu_encoder_virt

[Sean Paul <sean-p7yTbzM4H96eqtR555YLDQ@public.gmane.org>]

On Mon, Nov 12, 2018 at 05:43:17PM -0800, Jeykumar Sankaran wrote:
> On 2018-11-12 11:42, Sean Paul wrote:
> > From: Sean Paul <seanpaul@chromium.org>
> > 
> > Add a bool to dpu_encoder_virt to track whether the encoder is enabled
> > or not. Repurpose the enc_lock mutex to ensure that it is consistent
> > with the hw state.
> > 
> > Signed-off-by: Sean Paul <seanpaul@chromium.org>
> > ---
> >  drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c | 27 +++++++++++++++++----
> >  1 file changed, 22 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > index 10a0676d1dcf..3daa86220d47 100644
> > --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder.c
> > @@ -132,6 +132,7 @@ enum dpu_enc_rc_states {
> >   * @base:		drm_encoder base class for registration with DRM
> >   * @enc_spinlock:	Virtual-Encoder-Wide Spin Lock for IRQ purposes
> >   * @bus_scaling_client:	Client handle to the bus scaling interface
> > + * @enabled:		True if the encoder is active, protected by
> > enc_lock
> >   * @num_phys_encs:	Actual number of physical encoders contained.
> >   * @phys_encs:		Container of physical encoders managed.
> >   * @cur_master:		Pointer to the current master in this
> > mode. Optimization
> > @@ -148,8 +149,8 @@ enum dpu_enc_rc_states {
> >   *				all CTL paths
> >   * @crtc_kickoff_cb_data:	Opaque user data given to crtc_kickoff_cb
> >   * @debugfs_root:		Debug file system root file node
> > - * @enc_lock:			Lock around physical encoder
> > create/destroy and
> > -				access.
> > + * @enc_lock:			Lock around physical encoder
> > + *				create/destroy/enable/disable
> >   * @frame_busy_mask:		Bitmask tracking which phys_enc we are
> > still
> >   *				busy processing current command.
> >   *				Bit0 = phys_encs[0] etc.
> > @@ -175,6 +176,8 @@ struct dpu_encoder_virt {
> >  	spinlock_t enc_spinlock;
> >  	uint32_t bus_scaling_client;
> > 
> > +	bool enabled;
> > +
> >  	unsigned int num_phys_encs;
> >  	struct dpu_encoder_phys *phys_encs[MAX_PHYS_ENCODERS_PER_VIRTUAL];
> >  	struct dpu_encoder_phys *cur_master;
> > @@ -1121,6 +1124,8 @@ static void dpu_encoder_virt_enable(struct
> > drm_encoder *drm_enc)
> >  		return;
> >  	}
> >  	dpu_enc = to_dpu_encoder_virt(drm_enc);
> > +
> > +	mutex_lock(&dpu_enc->enc_lock);
> >  	cur_mode = &dpu_enc->base.crtc->state->adjusted_mode;
> > 
> >  	trace_dpu_enc_enable(DRMID(drm_enc), cur_mode->hdisplay,
> > @@ -1137,10 +1142,15 @@ static void dpu_encoder_virt_enable(struct
> > drm_encoder *drm_enc)
> >  	if (ret) {
> >  		DPU_ERROR_ENC(dpu_enc, "dpu resource control failed:
> > %d\n",
> >  				ret);
> > -		return;
> > +		goto out;
> >  	}
> > 
> >  	_dpu_encoder_virt_enable_helper(drm_enc);
> > +
> > +	dpu_enc->enabled = true;
> > +
> > +out:
> > +	mutex_unlock(&dpu_enc->enc_lock);
> >  }
> > 
> >  static void dpu_encoder_virt_disable(struct drm_encoder *drm_enc)
> > @@ -1162,11 +1172,14 @@ static void dpu_encoder_virt_disable(struct
> > drm_encoder *drm_enc)
> >  		return;
> >  	}
> > 
> > -	mode = &drm_enc->crtc->state->adjusted_mode;
> > -
> >  	dpu_enc = to_dpu_encoder_virt(drm_enc);
> >  	DPU_DEBUG_ENC(dpu_enc, "\n");
> > 
> > +	mutex_lock(&dpu_enc->enc_lock);
> Where do you expect it to go wrong if enable/disable
> is not protected using enc_lock?

runtime_resume can run concurrently with either enable or disable. We need the
enc_lock to ensure that enable/disable/runtime_resume are all relatively atomic.

Sean


> 
> Thanks and Regards,
> Jeykumar S.
> > +	dpu_enc->enabled = false;
> > +
> > +	mode = &drm_enc->crtc->state->adjusted_mode;
> > +
> >  	priv = drm_enc->dev->dev_private;
> >  	dpu_kms = to_dpu_kms(priv->kms);
> > 
> > @@ -1200,6 +1213,8 @@ static void dpu_encoder_virt_disable(struct
> > drm_encoder *drm_enc)
> >  	DPU_DEBUG_ENC(dpu_enc, "encoder disabled\n");
> > 
> >  	dpu_rm_release(&dpu_kms->rm, drm_enc);
> > +
> > +	mutex_unlock(&dpu_enc->enc_lock);
> >  }
> > 
> >  static enum dpu_intf dpu_encoder_get_intf(struct dpu_mdss_cfg *catalog,
> > @@ -2233,6 +2248,8 @@ struct drm_encoder *dpu_encoder_init(struct
> > drm_device *dev,
> > 
> >  	drm_encoder_helper_add(&dpu_enc->base, &dpu_encoder_helper_funcs);
> > 
> > +	dpu_enc->enabled = false;
> > +
> >  	return &dpu_enc->base;
> >  }
> 
> -- 
> Jeykumar S

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