mailbox: imx: support channel type tx doorbell v2

The Message Unit(MU) General Purpose Control registers are used for
TX doorbell, but there is no hardware ACK support.

The current TX doorbell channel is using tasklet to emulate hardware
ACK support to kick the TX tick from controller driver side.

The new added TX doorbell channel V2 not using tasklet to emulate the
hardware ACK support. The behavior for the channel is just writing the
GCR register, and no else. This will be used for SCMI mailbox.
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

drivers/mailbox/imx-mailbox.c

@@ -20,7 +20,9 @@
 #include <linux/suspend.h>
 #include <linux/slab.h>
 
-#define IMX_MU_CHANS		17
+#include "mailbox.h"
+
+#define IMX_MU_CHANS		24
 /* TX0/RX0/RXDB[0-3] */
 #define IMX_MU_SCU_CHANS	6
 /* TX0/RX0 */
@@ -39,6 +41,7 @@ enum imx_mu_chan_type {
 	IMX_MU_TYPE_TXDB	= 2, /* Tx doorbell */
 	IMX_MU_TYPE_RXDB	= 3, /* Rx doorbell */
 	IMX_MU_TYPE_RST		= 4, /* Reset */
+	IMX_MU_TYPE_TXDB_V2	= 5, /* Tx doorbell with S/W ACK */
 };
 
 enum imx_mu_xcr {
@@ -226,6 +229,9 @@ static int imx_mu_generic_tx(struct imx_mu_priv *priv,
 		imx_mu_xcr_rmw(priv, IMX_MU_GCR, IMX_MU_xCR_GIRn(priv->dcfg->type, cp->idx), 0);
 		tasklet_schedule(&cp->txdb_tasklet);
 		break;
+	case IMX_MU_TYPE_TXDB_V2:
+		imx_mu_xcr_rmw(priv, IMX_MU_GCR, IMX_MU_xCR_GIRn(priv->dcfg->type, cp->idx), 0);
+		break;
 	default:
 		dev_warn_ratelimited(priv->dev, "Send data on wrong channel type: %d\n", cp->type);
 		return -EINVAL;
@@ -554,6 +560,9 @@ static int imx_mu_startup(struct mbox_chan *chan)
 	int ret;
 
 	pm_runtime_get_sync(priv->dev);
+	if (cp->type == IMX_MU_TYPE_TXDB_V2)
+		return 0;
+
 	if (cp->type == IMX_MU_TYPE_TXDB) {
 		/* Tx doorbell don't have ACK support */
 		tasklet_init(&cp->txdb_tasklet, imx_mu_txdb_tasklet,
@@ -595,6 +604,11 @@ static void imx_mu_shutdown(struct mbox_chan *chan)
 	int ret;
 	u32 sr;
 
+	if (cp->type == IMX_MU_TYPE_TXDB_V2) {
+		pm_runtime_put_sync(priv->dev);
+		return;
+	}
+
 	if (cp->type == IMX_MU_TYPE_TXDB) {
 		tasklet_kill(&cp->txdb_tasklet);
 		pm_runtime_put_sync(priv->dev);
@@ -671,6 +685,7 @@ static struct mbox_chan *imx_mu_specific_xlate(struct mbox_controller *mbox,
 static struct mbox_chan * imx_mu_xlate(struct mbox_controller *mbox,
 				       const struct of_phandle_args *sp)
 {
+	struct mbox_chan *p_chan;
 	u32 type, idx, chan;
 
 	if (sp->args_count != 2) {
@@ -680,14 +695,25 @@ static struct mbox_chan * imx_mu_xlate(struct mbox_controller *mbox,
 
 	type = sp->args[0]; /* channel type */
 	idx = sp->args[1]; /* index */
-	chan = type * 4 + idx;
 
+	/* RST only supports 1 channel */
+	if ((type == IMX_MU_TYPE_RST) && idx) {
+		dev_err(mbox->dev, "Invalid RST channel %d\n", idx);
+		return ERR_PTR(-EINVAL);
+	}
+
+	chan = type * 4 + idx;
 	if (chan >= mbox->num_chans) {
 		dev_err(mbox->dev, "Not supported channel number: %d. (type: %d, idx: %d)\n", chan, type, idx);
 		return ERR_PTR(-EINVAL);
 	}
 
-	return &mbox->chans[chan];
+	p_chan = &mbox->chans[chan];
+
+	if (type == IMX_MU_TYPE_TXDB_V2)
+		p_chan->txdone_method = TXDONE_BY_ACK;
+
+	return p_chan;
 }
 
 static struct mbox_chan *imx_mu_seco_xlate(struct mbox_controller *mbox,