[PATCH v5 12/19] drm: writeback: Cleanup job ownership handling when queuing job

[Brian Starkey]

On Thu, Feb 21, 2019 at 12:42:25PM +0200, Laurent Pinchart wrote:
> Forgot to CC Eric, sorry about that.
> 
> On Thu, Feb 21, 2019 at 12:32:05PM +0200, Laurent Pinchart wrote:
> > The drm_writeback_queue_job() function takes ownership of the passed job
> > and requires the caller to manually set the connector state
> > writeback_job pointer to NULL. To simplify drivers and avoid errors
> > (such as the missing NULL set in the vc4 driver), pass the connector
> > state pointer to the function instead of the job pointer, and set the
> > writeback_job pointer to NULL internally.

LGTM, it was a mistake not doing it like this from the start.

I do have one suggestion below, but either way:

Reviewed-by: Brian Starkey <brian.starkey at arm.com>

> > 
> > Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas at ideasonboard.com>
> > ---
> >  drivers/gpu/drm/arm/malidp_mw.c |  3 +--
> >  drivers/gpu/drm/drm_writeback.c | 15 ++++++++++-----
> >  drivers/gpu/drm/vc4/vc4_txp.c   |  2 +-
> >  include/drm/drm_writeback.h     |  2 +-
> >  4 files changed, 13 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/arm/malidp_mw.c b/drivers/gpu/drm/arm/malidp_mw.c
> > index 041a64dc7167..87627219ce3b 100644
> > --- a/drivers/gpu/drm/arm/malidp_mw.c
> > +++ b/drivers/gpu/drm/arm/malidp_mw.c
> > @@ -252,8 +252,7 @@ void malidp_mw_atomic_commit(struct drm_device *drm,
> >  				     &mw_state->addrs[0],
> >  				     mw_state->format);
> >  
> > -		drm_writeback_queue_job(mw_conn, conn_state->writeback_job);
> > -		conn_state->writeback_job = NULL;
> > +		drm_writeback_queue_job(mw_conn, conn_state);
> >  		hwdev->hw->enable_memwrite(hwdev, mw_state->addrs,
> >  					   mw_state->pitches, mw_state->n_planes,
> >  					   fb->width, fb->height, mw_state->format,
> > diff --git a/drivers/gpu/drm/drm_writeback.c b/drivers/gpu/drm/drm_writeback.c
> > index c20e6fe00cb3..338b993d7c9f 100644
> > --- a/drivers/gpu/drm/drm_writeback.c
> > +++ b/drivers/gpu/drm/drm_writeback.c
> > @@ -242,11 +242,12 @@ EXPORT_SYMBOL(drm_writeback_connector_init);
> >  /**
> >   * drm_writeback_queue_job - Queue a writeback job for later signalling
> >   * @wb_connector: The writeback connector to queue a job on
> > - * @job: The job to queue
> > + * @conn_state: The connector state containing the job to queue
> >   *
> > - * This function adds a job to the job_queue for a writeback connector. It
> > - * should be considered to take ownership of the writeback job, and so any other
> > - * references to the job must be cleared after calling this function.
> > + * This function adds the job contained in @conn_state to the job_queue for a
> > + * writeback connector. It takes ownership of the writeback job and sets the
> > + * @conn_state->writeback_job to NULL, and so no access to the job may be
> > + * performed by the caller after this function returns.
> >   *
> >   * Drivers must ensure that for a given writeback connector, jobs are queued in
> >   * exactly the same order as they will be completed by the hardware (and
> > @@ -258,10 +259,14 @@ EXPORT_SYMBOL(drm_writeback_connector_init);
> >   * See also: drm_writeback_signal_completion()
> >   */
> >  void drm_writeback_queue_job(struct drm_writeback_connector *wb_connector,
> > -			     struct drm_writeback_job *job)
> > +			     struct drm_connector_state *conn_state)
> >  {
> > +	struct drm_writeback_job *job;
> >  	unsigned long flags;
> >  
> > +	job = conn_state->writeback_job;

What do you think about adding a defensive WARN_ON(!job)?

> > +	conn_state->writeback_job = NULL;
> > +
> >  	spin_lock_irqsave(&wb_connector->job_lock, flags);
> >  	list_add_tail(&job->list_entry, &wb_connector->job_queue);
> >  	spin_unlock_irqrestore(&wb_connector->job_lock, flags);
> > diff --git a/drivers/gpu/drm/vc4/vc4_txp.c b/drivers/gpu/drm/vc4/vc4_txp.c
> > index aa279b5b0de7..5dabd91f2d7e 100644
> > --- a/drivers/gpu/drm/vc4/vc4_txp.c
> > +++ b/drivers/gpu/drm/vc4/vc4_txp.c
> > @@ -327,7 +327,7 @@ static void vc4_txp_connector_atomic_commit(struct drm_connector *conn,
> >  
> >  	TXP_WRITE(TXP_DST_CTRL, ctrl);
> >  
> > -	drm_writeback_queue_job(&txp->connector, conn_state->writeback_job);
> > +	drm_writeback_queue_job(&txp->connector, conn_state);
> >  }
> >  
> >  static const struct drm_connector_helper_funcs vc4_txp_connector_helper_funcs = {
> > diff --git a/include/drm/drm_writeback.h b/include/drm/drm_writeback.h
> > index 23df9d463003..47662c362743 100644
> > --- a/include/drm/drm_writeback.h
> > +++ b/include/drm/drm_writeback.h
> > @@ -123,7 +123,7 @@ int drm_writeback_connector_init(struct drm_device *dev,
> >  				 const u32 *formats, int n_formats);
> >  
> >  void drm_writeback_queue_job(struct drm_writeback_connector *wb_connector,
> > -			     struct drm_writeback_job *job);
> > +			     struct drm_connector_state *conn_state);
> >  
> >  void drm_writeback_cleanup_job(struct drm_writeback_job *job);
> >  
> 
> -- 
> Regards,
> 
> Laurent Pinchart
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