drm/vmwgfx: Fix a potential infinite spin waiting for fifo idle

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@vmware.com>
Reported-by: Mark Sheldon <markshel@vmware.com>
Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>
Reivewed-by: Mark Sheldon <markshel@vmware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c b/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c
index 6ccd993..6eae14d 100644 (file)
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_fifo.c
@@ -180,8 +180,9 @@ void vmw_fifo_release(struct vmw_private *dev_priv, struct vmw_fifo_state *fifo)
 
        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);