[Intel-gfx] [PATCH 0/2] Fix live busy stats selftest failure

Umesh Nerlige Ramappa
2022-11-05T00:32:44Z

Engine busyness samples around a 10ms period is failing with busyness
ranging approx. from 87% to 115%. The expected range is +/- 5% of the
sample period.

When determining busyness of active engine, the GuC based engine
busyness implementation relies on a 64 bit timestamp register read. The
latency incurred by this register read causes the failure.

On DG1, when the test fails, the observed latencies range from 900us -
1.5ms.

In order to make the selftest more robust and account for such
latencies, increase the sample period to 100 ms.

v2: (Tvrtko)
In addition refactor intel_uncore_read64_2x32 to obtain the forcewake
once before reading upper and lower register dwords.

Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>

Umesh Nerlige Ramappa (2):
i915/uncore: Acquire fw before loop in intel_uncore_read64_2x32
drm/i915/selftest: Bump up sample period for busy stats selftest

drivers/gpu/drm/i915/gt/selftest_engine_pm.c | 2 +-
drivers/gpu/drm/i915/intel_uncore.h | 44 +++++++++++++-------
2 files changed, 31 insertions(+), 15 deletions(-)

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2.36.1