[Intel-gfx] [PATCH 2/2] drm/i915: Add WaKBLVECSSemaphoreWaitPoll

[Mika Kuoppala]

Chris Wilson <chris at chris-wilson.co.uk> writes:

> Quoting Mika Kuoppala (2018-05-30 16:02:06)
>> 
>> For the second issue where unlimited semaphore wait poll loop
>> is generating the heavy memory traffic and preventing a reset,
>> we add one microsecond poll interval to semaphore wait to
>> guarantee bandwidth for the reset preration. The side effect
>> is that we make semaphore completion latencies also 1us longer.
>
> You know the rule: second issue, second patch. That's odd, I would have
> expected a MI_SEMA op to be an arbitration point (even inside the busy
> wait loop), so would have expected it to behave nicely with STOP_RING.

My interpretation was that the context save gets delayed/stuck.

-Mika