drm/i915: Order assert forcewake test

Read the current value before computing the expected to ensure that if
the timer does complete early (against our will), it should not cause a
false positive.

v2: The local irq disable did not prevent the timer from running.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111074
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190705074604.16496-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/intel_uncore.c b/drivers/gpu/drm/i915/intel_uncore.c
index 2042c94..bb9e0da 100644 (file)
--- a/drivers/gpu/drm/i915/intel_uncore.c
+++ b/drivers/gpu/drm/i915/intel_uncore.c
@@ -758,19 +758,18 @@ void assert_forcewakes_active(struct intel_uncore *uncore,
         * Check that the caller has an explicit wakeref and we don't mistake
         * it for the auto wakeref.
         */
-       local_irq_disable();
        for_each_fw_domain_masked(domain, fw_domains, uncore, tmp) {
+               unsigned int actual = READ_ONCE(domain->wake_count);
                unsigned int expect = 1;
 
                if (hrtimer_active(&domain->timer) && READ_ONCE(domain->active))
                        expect++; /* pending automatic release */
 
-               if (WARN(domain->wake_count < expect,
+               if (WARN(actual < expect,
                         "Expected domain %d to be held awake by caller, count=%d\n",
-                        domain->id, domain->wake_count))
+                        domain->id, actual))
                        break;
        }
-       local_irq_enable();
 }
 
 /* We give fast paths for the really cool registers */