On Wed, May 10, 2017 at 05:31:02PM +0200, Michal Wajdeczko wrote:
> On Wed, May 10, 2017 at 05:07:01PM +0200, Daniel Vetter wrote:
> > The unconditionally fallback to the blocking wait_for resulted in
> > impressive fireworks at boot-up on my snb here. Make sure if we set
> > the slow timeout to 0 that we never ever sleep. The tail of the
> > callchain was
> >
> > intel_wait_for_register
> > -> __intel_wait_for_register_fw
> > -> usleep_range
> > -> BOOM
> >
> > It blew up in intel_crt_detect load detection code on the
> > ADPA_CRT_HOTPLUG_FORCE_TRIGGER in the ADPA register.
> >
>
> Hmm, by reading the code, it looks that call stack should be like this:
>
> -> intel_wait_for_register(..., timeout_ms=1000)
> -> __intel_wait_for_register_fw(..., fast_us=2, slow_ms=0, NULL);
> -> wait_for(..., MS=1000)
> -> _wait_for(..., US=1000*1000, W=1000)
> -> usleep_range(W, 2*W)
>
> so the slow_timeout_ms will be 0 in __intel_wait_for_register_fw()
>
> Are you sure that fix below is in right place?
The wait_for is _within the __intel_wait_for_register_fw. I've left out
the macros because those don't show up in the bt. We do _not_ blow up on
the wait_for after the __intel_wait_for_register_fw call in
intel_wait_for_register.
-Daniel
>
> -Michal
>
>
>
> > Fixes: 0564654340e2 ("drm/i915: Acquire uncore.lock over intel_uncore_wait_for_register()")
> > Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Cc: Michal Wajdeczko <michal.wajdeczko@xxxxxxxxx>
> > Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> > Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> > Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> > Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
> > Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx>
> > ---
> > drivers/gpu/drm/i915/intel_uncore.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
> > index aa9d3065853c..b03ad06bc3b6 100644
> > --- a/drivers/gpu/drm/i915/intel_uncore.c
> > +++ b/drivers/gpu/drm/i915/intel_uncore.c
> > @@ -1609,7 +1609,7 @@ int __intel_wait_for_register_fw(struct drm_i915_private *dev_priv,
> > ret = -ETIMEDOUT;
> > if (fast_timeout_us && fast_timeout_us <= 20000)
> > ret = _wait_for_atomic(done, fast_timeout_us, 0);
> > - if (ret)
> > + if (ret && slow_timeout_ms)
> > ret = wait_for(done, slow_timeout_ms);
> >
> > if (out_value)
> > --
> > 2.5.5
> >
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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