gpu: ipu-v3: ipu-dmfc: Protect function ipu_dmfc_init_channel() with mutex

To avoid race condition issue, we should protect the function
ipu_dmfc_init_channel() with the mutex dmfc->priv->mutex, since it
configures the register DMFC_GENERAL1 at runtime which contains
several control bits for various display channels.  This matches
better with fine grained locking logic in upper layer.

Signed-off-by: Liu Ying <gnuiyl@gmail.com>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

drivers/gpu/ipu-v3/ipu-dmfc.c

@@ -355,6 +355,8 @@ int ipu_dmfc_init_channel(struct dmfc_channel *dmfc, int width)
 	struct ipu_dmfc_priv *priv = dmfc->priv;
 	u32 dmfc_gen1;
 
+	mutex_lock(&priv->mutex);
+
 	dmfc_gen1 = readl(priv->base + DMFC_GENERAL1);
 
 	if ((dmfc->slots * 64 * 4) / width > dmfc->data->max_fifo_lines)
@@ -364,6 +366,8 @@ int ipu_dmfc_init_channel(struct dmfc_channel *dmfc, int width)
 
 	writel(dmfc_gen1, priv->base + DMFC_GENERAL1);
 
+	mutex_unlock(&priv->mutex);
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(ipu_dmfc_init_channel);