[Nouveau] [PATCH 6/6] drm/nouveau: give pgraph a chance to idle before spinlock

[Maarten Maathuis]

- Under some rare conditions i've managed to get pgraph errors after the
  channel is closed, which has very undesirable effects.
- This is the only reason i can think off.

Signed-off-by: Maarten Maathuis <madman2003 at gmail.com>
---
 drivers/gpu/drm/nouveau/nouveau_channel.c |   13 ++++++++++---
 1 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_channel.c b/drivers/gpu/drm/nouveau/nouveau_channel.c
index 86399f6..d25ed61 100644
--- a/drivers/gpu/drm/nouveau/nouveau_channel.c
+++ b/drivers/gpu/drm/nouveau/nouveau_channel.c
@@ -280,11 +280,18 @@ nouveau_channel_free(struct nouveau_channel *chan)
 	 */
 	nouveau_fence_fini(chan);
 
-	spin_lock_irqsave(&dev_priv->engine.lock, flags);
-
-	/* Ensure the channel is no longer active on the GPU */
+	/* This will prevent pfifo from switching channels. */
 	pfifo->reassign(dev, false);
 
+	/* We want to give pgraph a chance to idle and get rid of all potential
+	 * errors. We need to do this before the lock, otherwise the irq handler
+	 * is unable to process them.
+	 */
+	if (pgraph->channel(dev) == chan)
+		nouveau_wait_for_idle(dev);
+
+	spin_lock_irqsave(&dev_priv->engine.lock, flags);
+
 	pgraph->fifo_access(dev, false);
 	if (pgraph->channel(dev) == chan)
 		pgraph->unload_context(dev);
-- 
1.6.6.1