drm/i915: Fix __wait_seqno to use true infinite timeouts

When we switched to always using a timeout in conjunction with
wait_seqno, we lost the ability to detect missed interrupts. Since, we
have had issues with interrupts on a number of generations, and they are
required to be delivered in a timely fashion for a smooth UX, it is
important that we do log errors found in the wild and prevent the
display stalling for upwards of 1s every time the seqno interrupt is
missed.

Rather than continue to fix up the timeouts to work around the interface
impedence in wait_event_*(), open code the combination of
wait_event[_interruptible][_timeout], and use the exposed timer to
poll for seqno should we detect a lost interrupt.

v2: In order to satisfy the debug requirement of logging missed
interrupts with the real world requirments of making machines work even
if interrupts are hosed, we revert to polling after detecting a missed
interrupt.

v3: Throw in a debugfs interface to simulate broken hw not reporting
interrupts.

v4: s/EGAIN/EAGAIN/ (Imre)

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Imre Deak <imre.deak@intel.com>
[danvet: Don't use the struct typedef in new code.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 08e96a8c01aa..79bbcf925e4a 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1013,6 +1013,9 @@ struct i915_gpu_error {
 	struct drm_i915_error_state *first_error;
 	struct work_struct work;
 
+
+	unsigned long missed_irq_rings;
+
 	/**
 	 * State variable and reset counter controlling the reset flow
 	 *
@@ -1051,6 +1054,9 @@ struct i915_gpu_error {
 
 	/* For gpu hang simulation. */
 	unsigned int stop_rings;
+
+	/* For missed irq/seqno simulation. */
+	unsigned int test_irq_rings;
 };
 
 enum modeset_restore {