[PATCH 3.2 018/102] drm/vmwgfx: Fix a potential infinite spin waiting for fifo idle

[Ben Hutchings]

3.2.64-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Thomas Hellstrom <thellstrom@xxxxxxxxxx>

commit f01ea0c3d9db536c64d47922716d8b3b8f21d850 upstream.

The code waiting for fifo idle was incorrect and could possibly spin
forever under certain circumstances.

Signed-off-by: Thomas Hellstrom <thellstrom@xxxxxxxxxx>
Reported-by: Mark Sheldon <markshel@xxxxxxxxxx>
Reviewed-by: Jakob Bornecrantz <jakob@xxxxxxxxxx>
Reivewed-by: Mark Sheldon <markshel@xxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c
@@ -163,8 +163,9 @@ void vmw_fifo_release(struct vmw_private
 
 	mutex_lock(&dev_priv->hw_mutex);
 
+	vmw_write(dev_priv, SVGA_REG_SYNC, SVGA_SYNC_GENERIC);
 	while (vmw_read(dev_priv, SVGA_REG_BUSY) != 0)
-		vmw_write(dev_priv, SVGA_REG_SYNC, SVGA_SYNC_GENERIC);
+		;
 
 	dev_priv->last_read_seqno = ioread32(fifo_mem + SVGA_FIFO_FENCE);
 

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