Re: [PATCH v1 5/8] drm/panthor: Fix immediate ticking on a disabled tick

[Boris Brezillon <boris.brezillon@collabora.com>]

On Thu, 6 Nov 2025 16:23:24 +0000
Steven Price <steven.price@arm.com> wrote:

> On 06/11/2025 14:46, Boris Brezillon wrote:
> > We have a few path where we schedule the tick work immediately without  
> NIT: s/path/paths/> changing the resched_target. If the tick was
> stopped, this would lead
> > to a remaining_jiffies that's always > 0, and it wouldn't force a full
> > tick in that case. Add extra checks to cover that case properly.
> > 
> > Fixes: de8548813824 ("drm/panthor: Add the scheduler logical block")
> > Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
> > ---
> >  drivers/gpu/drm/panthor/panthor_sched.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/panthor/panthor_sched.c
> > index b6489e9ba1f0..1eba56e7360d 100644
> > --- a/drivers/gpu/drm/panthor/panthor_sched.c
> > +++ b/drivers/gpu/drm/panthor/panthor_sched.c
> > @@ -2358,8 +2358,12 @@ static void tick_work(struct work_struct *work)
> >  	if (drm_WARN_ON(&ptdev->base, ret))
> >  		goto out_dev_exit;
> >  
> > -	if (time_before64(now, sched->resched_target))
> > +	if (sched->resched_target != U64_MAX &&
> > +	    time_before64(now, sched->resched_target))
> >  		remaining_jiffies = sched->resched_target - now;
> > +	else if (sched->resched_target == U64_MAX &&
> > +		 time_before64(now, sched->last_tick + sched->tick_period))
> > +		remaining_jiffies = sched->last_tick + sched->tick_period - now;  
> 
> I'm wondering if this would be cleaner with an extra variable (and a
> comment):
> 
>    u64 resched_target = sched->resched_target;
> 
>    /* If the tick is stopped, calculate when the next tick would be */
>    if (resched_target == U64_MAX)
> 	   resched_target = sched->last_tick + sched->tick_period;
> 
>    if (time_before64(now, resched_target)
> 	   remaining_jiffies = resched_target - now;
> 
> It at least avoids some repetition.

Yep that looks better expressed like that. I'll go for your suggestion
in the next version.