linux-kernel - Re: [Patch 06/35] media: ti-vpe: vpe: Do not perform job transaction atomically

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Date:   Mon, 24 Oct 2016 11:57:23 -0500
From:   Benoit Parrot <bparrot@...com>
To:     Hans Verkuil <hverkuil@...all.nl>
CC:     <linux-media@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [Patch 06/35] media: ti-vpe: vpe: Do not perform job transaction
 atomically

Hans Verkuil <hverkuil@...all.nl> wrote on Mon [2016-Oct-17 16:17:15 +0200]:
> On 09/28/2016 11:20 PM, Benoit Parrot wrote:
> > From: Nikhil Devshatwar <nikhil.nd@...com>
> > 
> > Current VPE driver does not start the job until all the buffers for
> > a transaction are not queued. When running in multiple context, this might
> 
> I think this should be: s/not queued/queued/, right?

Yep, will fix that.

> 
> > increase the processing latency.
> > 
> > Alternate solution would be to try to continue the same context as long as
> > buffers for the transaction are ready; else switch the context. This may
> > increase number of context switches but it reduces latency significantly.
> > 
> > In this approach, the job_ready always succeeds as long as there are
> > buffers on the CAPTURE and OUTPUT stream. Processing may start immediately
> > as the first 2 iterations don't need extra source buffers. Shift all the
> > source buffers after each iteration and remove the oldest buffer.
> > 
> > Also, with this removes the constraint of pre buffering 3 buffers before
> > call to STREAMON in case of de-interlacing.
> > 
> > Signed-off-by: Nikhil Devshatwar <nikhil.nd@...com>
> > Signed-off-by: Benoit Parrot <bparrot@...com>
> > ---
> >  drivers/media/platform/ti-vpe/vpe.c | 32 ++++++++++++++++----------------
> >  1 file changed, 16 insertions(+), 16 deletions(-)
> > 
> > diff --git a/drivers/media/platform/ti-vpe/vpe.c b/drivers/media/platform/ti-vpe/vpe.c
> > index a0b29685fb69..9c38eff5df46 100644
> > --- a/drivers/media/platform/ti-vpe/vpe.c
> > +++ b/drivers/media/platform/ti-vpe/vpe.c
> > @@ -898,15 +898,14 @@ static struct vpe_ctx *file2ctx(struct file *file)
> >  static int job_ready(void *priv)
> >  {
> >  	struct vpe_ctx *ctx = priv;
> > -	int needed = ctx->bufs_per_job;
> >  
> > -	if (ctx->deinterlacing && ctx->src_vbs[2] == NULL)
> > -		needed += 2;	/* need additional two most recent fields */
> > -
> > -	if (v4l2_m2m_num_src_bufs_ready(ctx->fh.m2m_ctx) < needed)
> > -		return 0;
> > -
> > -	if (v4l2_m2m_num_dst_bufs_ready(ctx->fh.m2m_ctx) < needed)
> > +	/*
> > +	 * This check is needed as this might be called directly from driver
> > +	 * When called by m2m framework, this will always satisy, but when
> 
> typo: satisfy

Will fix.

> 
> > +	 * called from vpe_irq, this might fail. (src stream with zero buffers)
> > +	 */
> > +	if (v4l2_m2m_num_src_bufs_ready(ctx->fh.m2m_ctx) <= 0 ||
> > +		v4l2_m2m_num_dst_bufs_ready(ctx->fh.m2m_ctx) <= 0)
> >  		return 0;
> >  
> >  	return 1;
> > @@ -1116,19 +1115,20 @@ static void device_run(void *priv)
> >  	struct sc_data *sc = ctx->dev->sc;
> >  	struct vpe_q_data *d_q_data = &ctx->q_data[Q_DATA_DST];
> >  
> > -	if (ctx->deinterlacing && ctx->src_vbs[2] == NULL) {
> > -		ctx->src_vbs[2] = v4l2_m2m_src_buf_remove(ctx->fh.m2m_ctx);
> > -		WARN_ON(ctx->src_vbs[2] == NULL);
> > -		ctx->src_vbs[1] = v4l2_m2m_src_buf_remove(ctx->fh.m2m_ctx);
> > -		WARN_ON(ctx->src_vbs[1] == NULL);
> > -	}
> > -
> >  	ctx->src_vbs[0] = v4l2_m2m_src_buf_remove(ctx->fh.m2m_ctx);
> >  	WARN_ON(ctx->src_vbs[0] == NULL);
> >  	ctx->dst_vb = v4l2_m2m_dst_buf_remove(ctx->fh.m2m_ctx);
> >  	WARN_ON(ctx->dst_vb == NULL);
> >  
> >  	if (ctx->deinterlacing) {
> > +
> > +		if (ctx->src_vbs[2] == NULL) {
> > +			ctx->src_vbs[2] = ctx->src_vbs[0];
> > +			WARN_ON(ctx->src_vbs[2] == NULL);
> > +			ctx->src_vbs[1] = ctx->src_vbs[0];
> > +			WARN_ON(ctx->src_vbs[1] == NULL);
> > +		}
> > +
> >  		/*
> >  		 * we have output the first 2 frames through line average, we
> >  		 * now switch to EDI de-interlacer
> > @@ -1349,7 +1349,7 @@ static irqreturn_t vpe_irq(int irq_vpe, void *data)
> >  	}
> >  
> >  	ctx->bufs_completed++;
> > -	if (ctx->bufs_completed < ctx->bufs_per_job) {
> > +	if (ctx->bufs_completed < ctx->bufs_per_job && job_ready(ctx)) {
> >  		device_run(ctx);
> >  		goto handled;
> >  	}
> > 
> 
> Regards,
> 
> 	Hans