[0/2] Fix live busy stats selftest failure

Message

Umesh Nerlige Ramappa Nov. 5, 2022, 12:32 a.m. UTC

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 <[e-mail]>

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(-)