Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> [ text/plain ]
> 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?
Patch 1? Yes we could.
-Mika
> -Chris
>
> --
> Chris Wilson, Intel Open Source Technology Centre
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