[Intel-gfx] [PATCH] drm/i915: Wait for a moment before forcibly resetting the device

[Chris Wilson]

During igt, we ask to reset the device if any requests are still
outstanding at the end of a test, as this quickly kills off any
erroneous hanging request streams that may escape a test. However, since
it may take the device a few milliseconds to flush itself after the end
of a normal test, *cough* guc *cough*, we may accidentally tell the
device to reset itself after it idles. If we wait a moment, our usual
I915_IDLE_ENGINES_TIMEOUT of 200ms (seems a bit high, but still better
than umpteen hangchecks!), we can differentiate better between a stuck
engine and a healthy one, and so avoid prematurely forcing the reset and
any extra complications that may entail.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala at intel.com>
---
 drivers/gpu/drm/i915/i915_debugfs.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 3b995f9fdc06..e46de507fea2 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -4051,7 +4051,8 @@ i915_drop_caches_set(void *data, u64 val)
 		  val, val & DROP_ALL);
 	wakeref = intel_runtime_pm_get(i915);
 
-	if (val & DROP_RESET_ACTIVE && !intel_engines_are_idle(i915))
+	if (val & DROP_RESET_ACTIVE &&
+	    wait_for(intel_engines_are_idle(i915), I915_IDLE_ENGINES_TIMEOUT))
 		i915_gem_set_wedged(i915);
 
 	/* No need to check and wait for gpu resets, only libdrm auto-restarts
-- 
2.20.1