Re: [PATCH 3/5] media: coda: Replace the threaded interrupt with a hard interrupt

[Philipp Zabel <p.zabel@pengutronix.de>]

On Fri, 2019-04-26 at 14:56 -0300, Ezequiel Garcia wrote:
> Hi Philipp,
> 
> Thanks for the quick review of the series.
> 
> On Fri, 2019-04-26 at 11:16 +0200, Philipp Zabel wrote:
> > On Thu, 2019-04-25 at 15:35 -0300, Ezequiel Garcia wrote:
> > > The current interrupt handler is doing very little, and not doing
> > > any non-atomic operations. Pretty much all it does is accessing
> > > a couple registers, taking a couple spinlocks and then signalling
> > > a completion.
> > > 
> > > There is no reason this should be a threaded interrupt handler,
> > > so move the handler to regular hard interrupt context.
> > > 
> > > Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
> > > ---
> > >  drivers/media/platform/coda/coda-common.c | 4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/media/platform/coda/coda-common.c b/drivers/media/platform/coda/coda-common.c
> > > index 1f53ca4effd2..617d4547ec82 100644
> > > --- a/drivers/media/platform/coda/coda-common.c
> > > +++ b/drivers/media/platform/coda/coda-common.c
> > > @@ -2789,8 +2789,8 @@ static int coda_probe(struct platform_device *pdev)
> > >  		return irq;
> > >  	}
> > >  
> > > -	ret = devm_request_threaded_irq(&pdev->dev, irq, NULL, coda_irq_handler,
> > > -			IRQF_ONESHOT, dev_name(&pdev->dev), dev);
> > > +	ret = devm_request_irq(&pdev->dev, irq, coda_irq_handler, 0,
> > > +			       dev_name(&pdev->dev), dev);
> > >  	if (ret < 0) {
> > >  		dev_err(&pdev->dev, "failed to request irq: %d\n", ret);
> > >  		return ret;
> > 
> > There is one thing that this would complicate. For at least H.264 I
> > know that we can pad the bitstream in reaction to a BIT_BUF_EMPTY
> > interrupt, to make a picture run finish successfully when it is stuck in
> >   buffer underrun condition. This would need to be done under the
> > bitstream_mutex in a threaded handler.
> > 
> 
> In this case, a top-half handler would still stand in good stead,
> as it would check the interrupt status, and fire the bottom-half
> threaded interrupt to handle the buffer underrun.

I agree, and the R-b stands.

regards
Philipp