drm/msm/gpu: Park scheduler threads for system suspend

In the system suspend path, we don't want to be racing with the
scheduler kthreads pushing additional queued up jobs to the hw
queue (ringbuffer).  So park them first.  While we are at it,
move the wait for active jobs to complete into the new system-
suspend path.
Signed-off-by: Rob Clark <robdclark@chromium.org>
Link: https://lore.kernel.org/r/20220310234611.424743-3-robdclark@gmail.com

drivers/gpu/drm/msm/adreno/adreno_device.c

@@ -619,22 +619,82 @@ static int active_submits(struct msm_gpu *gpu)
 static int adreno_runtime_suspend(struct device *dev)
 {
 	struct msm_gpu *gpu = dev_to_gpu(dev);
-	int remaining;
+
+	/*
+	 * We should be holding a runpm ref, which will prevent
+	 * runtime suspend.  In the system suspend path, we've
+	 * already waited for active jobs to complete.
+	 */
+	WARN_ON_ONCE(gpu->active_submits);
+
+	return gpu->funcs->pm_suspend(gpu);
+}
+
+static void suspend_scheduler(struct msm_gpu *gpu)
+{
+	int i;
+
+	/*
+	 * Shut down the scheduler before we force suspend, so that
+	 * suspend isn't racing with scheduler kthread feeding us
+	 * more work.
+	 *
+	 * Note, we just want to park the thread, and let any jobs
+	 * that are already on the hw queue complete normally, as
+	 * opposed to the drm_sched_stop() path used for handling
+	 * faulting/timed-out jobs.  We can't really cancel any jobs
+	 * already on the hw queue without racing with the GPU.
+	 */
+	for (i = 0; i < gpu->nr_rings; i++) {
+		struct drm_gpu_scheduler *sched = &gpu->rb[i]->sched;
+		kthread_park(sched->thread);
+	}
+}
+
+static void resume_scheduler(struct msm_gpu *gpu)
+{
+	int i;
+
+	for (i = 0; i < gpu->nr_rings; i++) {
+		struct drm_gpu_scheduler *sched = &gpu->rb[i]->sched;
+		kthread_unpark(sched->thread);
+	}
+}
+
+static int adreno_system_suspend(struct device *dev)
+{
+	struct msm_gpu *gpu = dev_to_gpu(dev);
+	int remaining, ret;
+
+	suspend_scheduler(gpu);
 
 	remaining = wait_event_timeout(gpu->retire_event,
 				       active_submits(gpu) == 0,
 				       msecs_to_jiffies(1000));
 	if (remaining == 0) {
 		dev_err(dev, "Timeout waiting for GPU to suspend\n");
-		return -EBUSY;
+		ret = -EBUSY;
+		goto out;
 	}
 
-	return gpu->funcs->pm_suspend(gpu);
+	ret = pm_runtime_force_suspend(dev);
+out:
+	if (ret)
+		resume_scheduler(gpu);
+
+	return ret;
 }
+
+static int adreno_system_resume(struct device *dev)
+{
+	resume_scheduler(dev_to_gpu(dev));
+	return pm_runtime_force_resume(dev);
+}
+
 #endif
 
 static const struct dev_pm_ops adreno_pm_ops = {
-	SET_SYSTEM_SLEEP_PM_OPS(pm_runtime_force_suspend, pm_runtime_force_resume)
+	SET_SYSTEM_SLEEP_PM_OPS(adreno_system_suspend, adreno_system_resume)
 	SET_RUNTIME_PM_OPS(adreno_runtime_suspend, adreno_runtime_resume, NULL)
 };