[Intel-gfx] [PATCH v2] drm/i915/selftests: Measure dispatch latency

Chris Wilson chris at chris-wilson.co.uk
Mon May 18 15:14:43 UTC 2020

Quoting Mika Kuoppala (2020-05-18 16:07:47)
> Chris Wilson <chris at chris-wilson.co.uk> writes:
> > +             cs = emit_timestamp_store(cs, ce, offset + i * sizeof(u32));
> Is the dual writes here so that when you kick the semaphore, you get the
> latest no matter which side you were on?

We wait on the first write in the CPU before releasing the semaphore. It
was easier to copy the code, but now it can be an emit_store_dw() to
make it clearer that we are not using it as timestamp -- and avoid the
infinite wait if we hit CS_TIMESTAMP == 0.

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