On Wed, Jan 29, 2014 at 01:37:53PM +0200, Jani Nikula wrote:
> On Wed, 29 Jan 2014, Imre Deak <imre.deak@xxxxxxxxx> wrote:
> > schedule_timeout_uninterruptible() takes jiffies not ms.
> >
> > Also we should check whether jiffies has overflowed since the timestamp
> > for event A was taken. This is highly unlikely on 64 bit, but on 32 bit
> > machines jiffies initially is -300*HZ. If the panel power is initially
> > off the first wait from edp_panel_vdd_on()->wait_panel_power_cycle()
> > will result in a call timestamp_jiffies of 0, so on 32 bit machines we
> > would wait ~300 sec + to_wait_ms. Fix this by checking if the initial
> > timestamp is not in the future.
> >
> > Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/i915_drv.h | 17 +++++++++--------
> > 1 file changed, 9 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> > index 3673ba1..6a80393 100644
> > --- a/drivers/gpu/drm/i915/i915_drv.h
> > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > @@ -2643,12 +2643,13 @@ timespec_to_jiffies_timeout(const struct timespec *value)
> > * doesn't happen exactly after event A, you record the timestamp (jiffies) of
> > * when event A happened, then just before event B you call this function and
> > * pass the timestamp as the first argument, and X as the second argument.
> > + * Note that the recorded timestamp (timestamp_jiffies) can't be in the future
> > + * otherwise the function won't wait at all.
> > */
> > static inline void
> > wait_remaining_ms_from_jiffies(unsigned long timestamp_jiffies, int to_wait_ms)
> > {
> > - unsigned long target_jiffies, tmp_jiffies;
> > - unsigned int remaining_ms;
> > + unsigned long target_jiffies, tmp_jiffies, remaining_jiffies;
> >
> > /*
> > * Don't re-read the value of "jiffies" every time since it may change
> > @@ -2658,12 +2659,12 @@ wait_remaining_ms_from_jiffies(unsigned long timestamp_jiffies, int to_wait_ms)
> > target_jiffies = timestamp_jiffies +
> > msecs_to_jiffies_timeout(to_wait_ms);
> >
> > - if (time_after(target_jiffies, tmp_jiffies)) {
> > - remaining_ms = jiffies_to_msecs((long)target_jiffies -
> > - (long)tmp_jiffies);
> > - while (remaining_ms)
> > - remaining_ms =
> > - schedule_timeout_uninterruptible(remaining_ms);
> > + if (time_after(target_jiffies, tmp_jiffies) &&
> > + time_before_eq(timestamp_jiffies, tmp_jiffies)) {
> > + remaining_jiffies = target_jiffies - tmp_jiffies;
> > + while (remaining_jiffies)
> > + remaining_jiffies =
> > + schedule_timeout_uninterruptible(remaining_jiffies);
> > }
> > }
>
> For the record, I spotted the jiffies vs. ms mistake in review [1],
> Paulo posted v5 [2], but apparently Daniel applied v4 anyway:
>
> commit dce56b3c626fb1d533258a624d42a1a3fc17da17
> Author: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx>
> Date: Thu Dec 19 14:29:40 2013 -0200
>
> drm/i915: save some time when waiting the eDP timings
>
> Wrap around was also discussed.
>
>
> BR,
> Jani.
>
> [1] http://mid.gmane.org/87fvpnkgyg.fsf@xxxxxxxxx
> [2] http://mid.gmane.org/1388778311-2020-1-git-send-email-przanoni@xxxxxxxxx
Oh dear, I'll hide in shame. Dunno how I've botched this one up, thanks
for catching it.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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