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?
-Michal
> Fixes: 0564654340e2 ("drm/i915: Acquire uncore.lock over
> intel_uncore_wait_for_register()")
> Cc: Chris Wilson <ch...@chris-wilson.co.uk>
> Cc: Michal Wajdeczko <michal.wajdec...@intel.com>
> Cc: Joonas Lahtinen <joonas.lahti...@linux.intel.com>
> Cc: Tvrtko Ursulin <tvrtko.ursu...@intel.com>
> Cc: Daniel Vetter <daniel.vet...@intel.com>
> Cc: Jani Nikula <jani.nik...@linux.intel.com>
> Reviewed-by: Chris Wilson <ch...@chris-wilson.co.uk>
> Signed-off-by: Daniel Vetter <daniel.vet...@intel.com>
> ---
> 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
>
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