---
V5:
  None
V4:
  None
V3:
  Check mbox fsl,imx8-mu-scu for fast_ipc

  drivers/firmware/imx/imx-scu.c | 54 +++++++++++++++++++++++++++++++++---------
  1 file changed, 43 insertions(+), 11 deletions(-)

diff --git a/drivers/firmware/imx/imx-scu.c b/drivers/firmware/imx/imx-scu.c
index f71eaa5bf52d..e94a5585b698 100644
--- a/drivers/firmware/imx/imx-scu.c
+++ b/drivers/firmware/imx/imx-scu.c

@@ -38,6 +38,7 @@ struct imx_sc_ipc {
  	struct device *dev;
  	struct mutex lock;
  	struct completion done;
+	bool fast_ipc;
  
  	/* temporarily store the SCU msg */
  	u32 *msg;

@@ -115,6 +116,7 @@ static void imx_scu_rx_callback(struct mbox_client *c, void *msg)
  	struct imx_sc_ipc *sc_ipc = sc_chan->sc_ipc;
  	struct imx_sc_rpc_msg *hdr;
  	u32 *data = msg;
+	int i;
  
  	if (!sc_ipc->msg) {
  		dev_warn(sc_ipc->dev, "unexpected rx idx %d 0x%08x, ignore!\n",

@@ -122,6 +124,19 @@ static void imx_scu_rx_callback(struct mbox_client *c, void *msg)
  		return;
  	}
  
+	if (sc_ipc->fast_ipc) {
+		hdr = msg;
+		sc_ipc->rx_size = hdr->size;
+		sc_ipc->msg[0] = *data++;
+
+		for (i = 1; i < sc_ipc->rx_size; i++)
+			sc_ipc->msg[i] = *data++;
+
+		complete(&sc_ipc->done);
+
+		return;
+	}
+
  	if (sc_chan->idx == 0) {
  		hdr = msg;
  		sc_ipc->rx_size = hdr->size;

@@ -147,6 +162,7 @@ static int imx_scu_ipc_write(struct imx_sc_ipc *sc_ipc, void *msg)
  	struct imx_sc_chan *sc_chan;
  	u32 *data = msg;
  	int ret;
+	int size;
  	int i;
  
  	/* Check size */

@@ -156,7 +172,8 @@ static int imx_scu_ipc_write(struct imx_sc_ipc *sc_ipc, void *msg)
  	dev_dbg(sc_ipc->dev, "RPC SVC %u FUNC %u SIZE %u\n", hdr->svc,
  		hdr->func, hdr->size);
  
-	for (i = 0; i < hdr->size; i++) {
+	size = sc_ipc->fast_ipc ? 1 : hdr->size;
+	for (i = 0; i < size; i++) {
  		sc_chan = &sc_ipc->chans[i % 4];
  
  		/*

@@ -168,8 +185,10 @@ static int imx_scu_ipc_write(struct imx_sc_ipc *sc_ipc, void *msg)
  		 * Wait for tx_done before every send to ensure that no
  		 * queueing happens at the mailbox channel level.
  		 */
-		wait_for_completion(&sc_chan->tx_done);
-		reinit_completion(&sc_chan->tx_done);
+		if (!sc_ipc->fast_ipc) {
+			wait_for_completion(&sc_chan->tx_done);
+			reinit_completion(&sc_chan->tx_done);
+		}
  
  		ret = mbox_send_message(sc_chan->ch, &data[i]);
  		if (ret < 0)

@@ -246,6 +265,8 @@ static int imx_scu_probe(struct platform_device *pdev)
  	struct imx_sc_chan *sc_chan;
  	struct mbox_client *cl;
  	char *chan_name;
+	struct of_phandle_args args;
+	int num_channel;
  	int ret;
  	int i;
  

@@ -253,11 +274,20 @@ static int imx_scu_probe(struct platform_device *pdev)
  	if (!sc_ipc)
  		return -ENOMEM;
  
-	for (i = 0; i < SCU_MU_CHAN_NUM; i++) {
-		if (i < 4)
+	ret = of_parse_phandle_with_args(pdev->dev.of_node, "mboxes",
+					 "#mbox-cells", 0, &args);
+	if (ret)
+		return ret;
+
+	sc_ipc->fast_ipc = of_device_is_compatible(args.np, "fsl,imx8-mu-scu");
+
+	num_channel = sc_ipc->fast_ipc ? 2 : SCU_MU_CHAN_NUM;
+	for (i = 0; i < num_channel; i++) {
+		if (i < num_channel / 2)
  			chan_name = kasprintf(GFP_KERNEL, "tx%d", i);
  		else
-			chan_name = kasprintf(GFP_KERNEL, "rx%d", i - 4);
+			chan_name = kasprintf(GFP_KERNEL, "rx%d",
+					      i - num_channel / 2);
  
  		if (!chan_name)
  			return -ENOMEM;

@@ -269,13 +299,15 @@ static int imx_scu_probe(struct platform_device *pdev)
  		cl->knows_txdone = true;
  		cl->rx_callback = imx_scu_rx_callback;
  
-		/* Initial tx_done completion as "done" */
-		cl->tx_done = imx_scu_tx_done;
-		init_completion(&sc_chan->tx_done);
-		complete(&sc_chan->tx_done);
+		if (!sc_ipc->fast_ipc) {
+			/* Initial tx_done completion as "done" */
+			cl->tx_done = imx_scu_tx_done;
+			init_completion(&sc_chan->tx_done);
+			complete(&sc_chan->tx_done);
+		}
  
  		sc_chan->sc_ipc = sc_ipc;
-		sc_chan->idx = i % 4;
+		sc_chan->idx = i % (num_channel / 2);
  		sc_chan->ch = mbox_request_channel_byname(cl, chan_name);
  		if (IS_ERR(sc_chan->ch)) {
  			ret = PTR_ERR(sc_chan->ch);