[Intel-gfx] [PATCH 3/4] drm/i915/selftests: Hold the rpm/forcewake wakeref for the reset tests

[Chris Wilson]

Resetting the engine requires us to hold the forcewake wakeref to
prevent RC6 trying to happen in the middle of the reset sequence.
Normally, this is taken by i915_handle_error(), but as we are calling
the lowlevel functions ourselves, we need to hold it. Wrap the entire
live_hangcheck set of subtests in a single forcewake section for
simplicity.

This greatly improves the reliability of drv_selftest/live_hangcheck on
Haswell, where it would exhibit an inability to restart a request
because it lost its PD registers (PD_DIR_BASE reported as 0).

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
---
 drivers/gpu/drm/i915/selftests/intel_hangcheck.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/selftests/intel_hangcheck.c b/drivers/gpu/drm/i915/selftests/intel_hangcheck.c
index 7e1bdd88eda3..a9e0decccc1f 100644
--- a/drivers/gpu/drm/i915/selftests/intel_hangcheck.c
+++ b/drivers/gpu/drm/i915/selftests/intel_hangcheck.c
@@ -878,9 +878,18 @@ int intel_hangcheck_live_selftests(struct drm_i915_private *i915)
 		SUBTEST(igt_reset_queue),
 		SUBTEST(igt_handle_error),
 	};
+	int err;
 
 	if (!intel_has_gpu_reset(i915))
 		return 0;
 
-	return i915_subtests(tests, i915);
+	intel_runtime_pm_get(i915);
+	intel_uncore_forcewake_get(i915, FORCEWAKE_ALL);
+
+	err = i915_subtests(tests, i915);
+
+	intel_uncore_forcewake_put(i915, FORCEWAKE_ALL);
+	intel_runtime_pm_put(i915);
+
+	return err;
 }
-- 
2.14.2