[Intel-gfx] [PATCH] drm/i915: Don't wait forever in drop_caches

[John.C.Harrison at Intel.com]

From: John Harrison <John.C.Harrison at Intel.com>

At the end of each test, IGT does a drop caches call via sysfs with
special flags set. One of the possible paths waits for idle with an
infinite timeout. That causes problems for debugging issues when CI
catches a "can't go idle" test failure. Best case, the CI system times
out (after 90s), attempts a bunch of state dump actions and then
reboots the system to recover it. Worst case, the CI system can't do
anything at all and then times out (after 1000s) and simply reboots.
Sometimes a serial port log of dmesg might be available, sometimes not.

So rather than making life hard for ourselves, change the timeout to
be 10s rather than infinite. Also, trigger the standard
wedge/reset/recover sequence so that testing can continue with a
working system (if possible).

Signed-off-by: John Harrison <John.C.Harrison at Intel.com>
---
 drivers/gpu/drm/i915/i915_debugfs.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index ae987e92251dd..9d916fbbfc27c 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -641,6 +641,9 @@ DEFINE_SIMPLE_ATTRIBUTE(i915_perf_noa_delay_fops,
 		  DROP_RESET_ACTIVE | \
 		  DROP_RESET_SEQNO | \
 		  DROP_RCU)
+
+#define DROP_IDLE_TIMEOUT	(HZ * 10)
+
 static int
 i915_drop_caches_get(void *data, u64 *val)
 {
@@ -661,7 +664,9 @@ gt_drop_caches(struct intel_gt *gt, u64 val)
 		intel_gt_retire_requests(gt);
 
 	if (val & (DROP_IDLE | DROP_ACTIVE)) {
-		ret = intel_gt_wait_for_idle(gt, MAX_SCHEDULE_TIMEOUT);
+		ret = intel_gt_wait_for_idle(gt, DROP_IDLE_TIMEOUT);
+		if (ret == -ETIME)
+			intel_gt_set_wedged(gt);
 		if (ret)
 			return ret;
 	}
-- 
2.37.3