On Wed, May 18, 2016 at 10:20:22AM +0200, Daniel Vetter wrote:
> On Tue, May 17, 2016 at 06:43:24PM +0300, Mika Kuoppala wrote:
> > Usually the condition we are after appears within very short time.
> > Spin few times before going into sleep. With this approximately
> > half of the wait_for in init path will take the fast path without
> > sleeping.
> >
> > Signed-off-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxx>
>
> Some numbers on how much time this saved would be nice.
>
> Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
>
> > ---
> > drivers/gpu/drm/i915/intel_drv.h | 14 ++++++++++----
> > 1 file changed, 10 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
> > index 488141929a7a..c225605c727c 100644
> > --- a/drivers/gpu/drm/i915/intel_drv.h
> > +++ b/drivers/gpu/drm/i915/intel_drv.h
> > @@ -39,7 +39,7 @@
> > #include <drm/drm_atomic.h>
> >
> > /**
> > - * _wait_for_ms - magic (register) wait macro
> > + * __wait_for_ms - magic (register) wait macro
> > *
> > * Does the right thing for modeset paths when run under kdgb or similar atomic
> > * contexts. Note that it's important that we check the condition again after
> > @@ -50,17 +50,22 @@
> > * drm_can_sleep() can be removed and in_atomic()/!in_atomic() asserts
> > * added.
> > */
> > -#define _wait_for_ms(COND, TIMEOUT_MS, SLEEP_US) ({ \
> > +#define __wait_for_ms(COND, TIMEOUT_MS, SLEEP_US, SPIN_COUNT) ({ \
> > const unsigned long timeout__ = \
> > jiffies + msecs_to_jiffies(TIMEOUT_MS) + 1; \
> > + unsigned int c__ = 0; \
> > int ret__ = 0; \
> > + \
> > while (!(COND)) { \
> > if (time_after(jiffies, timeout__)) { \
> > if (!(COND)) \
> > ret__ = -ETIMEDOUT; \
> > break; \
> > } \
> > - if ((SLEEP_US) && drm_can_sleep()) { \
> > + \
> > + if (++c__ > (SPIN_COUNT) && \
> > + (SLEEP_US) && \
Could we kill SLEEP_US here in patch 0?
-Chris
--
Chris Wilson, Intel Open Source Technology Centre
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