drm/i915: Defer final intel_wakeref_put to process context

As we need to acquire a mutex to serialise the final
intel_wakeref_put, we need to ensure that we are in process context at
that time. However, we want to allow operation on the intel_wakeref from
inside timer and other hardirq context, which means that need to defer
that final put to a workqueue.

Inside the final wakeref puts, we are safe to operate in any context, as
we are simply marking up the HW and state tracking for the potential
sleep. It's only the serialisation with the potential sleeping getting
that requires careful wait avoidance. This allows us to retain the
immediate processing as before (we only need to sleep over the same
races as the current mutex_lock).

v2: Add a selftest to ensure we exercise the code while lockdep watches.
v3: That test was extremely loud and complained about many things!
v4: Not a whale!

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111295
References: https://bugs.freedesktop.org/show_bug.cgi?id=111245
References: https://bugs.freedesktop.org/show_bug.cgi?id=111256
Fixes: 18398904ca9e ("drm/i915: Only recover active engines")
Fixes: 51fbd8de87dc ("drm/i915/pmu: Atomically acquire the gt_pm wakeref")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190808202758.10453-1-chris@chris-wilson.co.uk

1 files changed, 3 insertions, 23 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 6bae073fb570..67a0bc4db9cd 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -893,19 +893,6 @@ void i915_gem_runtime_suspend(struct drm_i915_private *i915)
 	}
 }
 
-static int wait_for_engines(struct intel_gt *gt)
-{
-	if (wait_for(intel_engines_are_idle(gt), I915_IDLE_ENGINES_TIMEOUT)) {
-		dev_err(gt->i915->drm.dev,
-			"Failed to idle engines, declaring wedged!\n");
-		GEM_TRACE_DUMP();
-		intel_gt_set_wedged(gt);
-		return -EIO;
-	}
-
-	return 0;
-}
-
 static long
 wait_for_timelines(struct drm_i915_private *i915,
 		   unsigned int flags, long timeout)
@@ -953,27 +940,20 @@ int i915_gem_wait_for_idle(struct drm_i915_private *i915,
 			   unsigned int flags, long timeout)
 {
 	/* If the device is asleep, we have no requests outstanding */
-	if (!READ_ONCE(i915->gt.awake))
+	if (!intel_gt_pm_is_awake(&i915->gt))
 		return 0;
 
-	GEM_TRACE("flags=%x (%s), timeout=%ld%s, awake?=%s\n",
+	GEM_TRACE("flags=%x (%s), timeout=%ld%s\n",
 		  flags, flags & I915_WAIT_LOCKED ? "locked" : "unlocked",
-		  timeout, timeout == MAX_SCHEDULE_TIMEOUT ? " (forever)" : "",
-		  yesno(i915->gt.awake));
+		  timeout, timeout == MAX_SCHEDULE_TIMEOUT ? " (forever)" : "");
 
 	timeout = wait_for_timelines(i915, flags, timeout);
 	if (timeout < 0)
 		return timeout;
 
 	if (flags & I915_WAIT_LOCKED) {
-		int err;
-
 		lockdep_assert_held(&i915->drm.struct_mutex);
 
-		err = wait_for_engines(&i915->gt);
-		if (err)
-			return err;
-
 		i915_retire_requests(i915);
 	}