Re: [PATCH 1/1] omap3isp: Fix sub-device power management code

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Sakari,

On Thursday 11 June 2015 00:38:11 Sakari Ailus wrote:
> On Wed, Jun 10, 2015 at 03:52:50AM +0300, Laurent Pinchart wrote:
> > On Friday 29 May 2015 02:17:47 Sakari Ailus wrote:
> > > The power management code was reworked a little due to interface changes
> > > in the MC. Due to those changes the power management broke a bit, fix it
> > > so the functionality is reverted to old behaviour.
> > 
> > I found the commit message a bit vague. How about
> > 
> > "Commit 813f5c0ac5cc ("media: Change media device link_notify behaviour")
> > modified the media controller link setup notification API and updated the
> > OMAP3 ISP driver accordingly. As a side effect it introduced a bug by
> > turning power on after setting the link instead of before. This results
> > in powered off entities being accessed. Fix it."
> > 
> > Or have I misunderstood the problem ?
> 
> Not entirely, but it's not just that: depending on the order in which the
> links are changed and the video nodes opened or closed, the use counts may
> end up being too high or too low (even negative).

OK. Could you please update the commit message accordingly ?

> >> Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
> >> Fixes: 813f5c0ac5cc [media] media: Change media device link_notify
> >> behaviour Cc: stable@vger.kernel.org # since v3.10
> >> ---
> >> 
> >>  drivers/media/platform/omap3isp/isp.c | 4 ++--
> >>  1 file changed, 2 insertions(+), 2 deletions(-)
> >> 
> >> diff --git a/drivers/media/platform/omap3isp/isp.c
> >> b/drivers/media/platform/omap3isp/isp.c index a038c05..3e6b97b 100644
> >> --- a/drivers/media/platform/omap3isp/isp.c
> >> +++ b/drivers/media/platform/omap3isp/isp.c
> >> @@ -829,14 +829,14 @@ static int isp_pipeline_link_notify(struct
> >> media_link *link, u32 flags,
> >> 	int ret;
> >> 
> >>  	if (notification == MEDIA_DEV_NOTIFY_POST_LINK_CH &&
> >> -	    !(link->flags & MEDIA_LNK_FL_ENABLED)) {
> >> +	    !(flags & MEDIA_LNK_FL_ENABLED)) {
> > 
> > Isn't link->flags == flags in the post notification callback ?
> 
> It is. IMO it's better to use flags here still. So below is the actual
> functional change.

No issue with that.

> >>  		/* Powering off entities is assumed to never fail. */
> >>  		isp_pipeline_pm_power(source, -sink_use);
> >>  		isp_pipeline_pm_power(sink, -source_use);
> >>  		return 0;
> >>  	}
> >> 
> >> -	if (notification == MEDIA_DEV_NOTIFY_POST_LINK_CH &&
> >> +	if (notification == MEDIA_DEV_NOTIFY_PRE_LINK_CH &&
> >>  		(flags & MEDIA_LNK_FL_ENABLED)) {
> >>  		ret = isp_pipeline_pm_power(source, sink_use);

-- 
Regards,

Laurent Pinchart