drm/nv50-nvc0: prevent multiple vm/bar flushes occuring simultanenously

The per-vm mutex doesn't prevent this completely, a flush coming from the
BAR VM could potentially happen at the same time as one for the channel
VM. Not to mention that if/when we get per-client/channel VM, this will
happen far more frequently.

Signed-off-by: Ben Skeggs <[e-mail]>
Signed-off-by: Dave Airlie <[e-mail]>

drivers/gpu/drm/nouveau/nv50_instmem.c

···
 void
 nv50_instmem_flush(struct drm_device *dev)
 {
+	struct drm_nouveau_private *dev_priv = dev->dev_private;
+
+	spin_lock(&dev_priv->ramin_lock);
 	nv_wr32(dev, 0x00330c, 0x00000001);
 	if (!nv_wait(dev, 0x00330c, 0x00000002, 0x00000000))
 		NV_ERROR(dev, "PRAMIN flush timeout\n");
+	spin_unlock(&dev_priv->ramin_lock);
 }
 
 void
 nv84_instmem_flush(struct drm_device *dev)
 {
+	struct drm_nouveau_private *dev_priv = dev->dev_private;
+
+	spin_lock(&dev_priv->ramin_lock);
 	nv_wr32(dev, 0x070000, 0x00000001);
 	if (!nv_wait(dev, 0x070000, 0x00000002, 0x00000000))
 		NV_ERROR(dev, "PRAMIN flush timeout\n");
+	spin_unlock(&dev_priv->ramin_lock);
 }
 

drivers/gpu/drm/nouveau/nv50_vm.c

···
 void
 nv50_vm_flush_engine(struct drm_device *dev, int engine)
 {
+	struct drm_nouveau_private *dev_priv = dev->dev_private;
+
+	spin_lock(&dev_priv->ramin_lock);
 	nv_wr32(dev, 0x100c80, (engine << 16) | 1);
 	if (!nv_wait(dev, 0x100c80, 0x00000001, 0x00000000))
 		NV_ERROR(dev, "vm flush timeout: engine %d\n", engine);
+	spin_unlock(&dev_priv->ramin_lock);
 }