firmware: arm_scmi: Segregate tx channel handling and prepare to add rx

The transmit(Tx) channels are specified as the first entry and the
receive(Rx) channels are the second entry as per the device tree
bindings. Since we currently just support Tx, index 0 is hardcoded at
all required callsites.

In order to prepare for adding Rx support, let's remove those hardcoded
index and add boolean parameter to identify Tx/Rx channels when setting
them up.
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

drivers/firmware/arm_scmi/driver.c

@@ -112,7 +112,7 @@ struct scmi_chan_info {
  * @version: SCMI revision information containing protocol version,
  *	implementation version and (sub-)vendor identification.
  * @minfo: Message info
- * @tx_idr: IDR object to map protocol id to channel info pointer
+ * @tx_idr: IDR object to map protocol id to Tx channel info pointer
  * @protocols_imp: List of protocols implemented, currently maximum of
  *	MAX_PROTOCOLS_IMP elements allocated by the base protocol
  * @node: List head
@@ -640,22 +640,27 @@ static int scmi_xfer_info_init(struct scmi_info *sinfo)
 	return 0;
 }
 
-static int scmi_mailbox_check(struct device_node *np)
+static int scmi_mailbox_check(struct device_node *np, int idx)
 {
-	return of_parse_phandle_with_args(np, "mboxes", "#mbox-cells", 0, NULL);
+	return of_parse_phandle_with_args(np, "mboxes", "#mbox-cells",
+					  idx, NULL);
 }
 
-static inline int
-scmi_mbox_chan_setup(struct scmi_info *info, struct device *dev, int prot_id)
+static int scmi_mbox_chan_setup(struct scmi_info *info, struct device *dev,
+				int prot_id, bool tx)
 {
-	int ret;
+	int ret, idx;
 	struct resource res;
 	resource_size_t size;
 	struct device_node *shmem, *np = dev->of_node;
 	struct scmi_chan_info *cinfo;
 	struct mbox_client *cl;
+	const char *desc = tx ? "Tx" : "Rx";
+
+	/* Transmit channel is first entry i.e. index 0 */
+	idx = tx ? 0 : 1;
 
-	if (scmi_mailbox_check(np)) {
+	if (scmi_mailbox_check(np, idx)) {
 		cinfo = idr_find(&info->tx_idr, SCMI_PROTOCOL_BASE);
 		goto idr_alloc;
 	}
@@ -669,31 +674,31 @@ scmi_mbox_chan_setup(struct scmi_info *info, struct device *dev, int prot_id)
 	cl = &cinfo->cl;
 	cl->dev = dev;
 	cl->rx_callback = scmi_rx_callback;
-	cl->tx_prepare = scmi_tx_prepare;
+	cl->tx_prepare = tx ? scmi_tx_prepare : NULL;
 	cl->tx_block = false;
-	cl->knows_txdone = true;
+	cl->knows_txdone = tx;
 
-	shmem = of_parse_phandle(np, "shmem", 0);
+	shmem = of_parse_phandle(np, "shmem", idx);
 	ret = of_address_to_resource(shmem, 0, &res);
 	of_node_put(shmem);
 	if (ret) {
-		dev_err(dev, "failed to get SCMI Tx payload mem resource\n");
+		dev_err(dev, "failed to get SCMI %s payload memory\n", desc);
 		return ret;
 	}
 
 	size = resource_size(&res);
 	cinfo->payload = devm_ioremap(info->dev, res.start, size);
 	if (!cinfo->payload) {
-		dev_err(dev, "failed to ioremap SCMI Tx payload\n");
+		dev_err(dev, "failed to ioremap SCMI %s payload\n", desc);
 		return -EADDRNOTAVAIL;
 	}
 
-	/* Transmit channel is first entry i.e. index 0 */
-	cinfo->chan = mbox_request_channel(cl, 0);
+	cinfo->chan = mbox_request_channel(cl, idx);
 	if (IS_ERR(cinfo->chan)) {
 		ret = PTR_ERR(cinfo->chan);
 		if (ret != -EPROBE_DEFER)
-			dev_err(dev, "failed to request SCMI Tx mailbox\n");
+			dev_err(dev, "failed to request SCMI %s mailbox\n",
+				desc);
 		return ret;
 	}
 
@@ -721,7 +726,7 @@ scmi_create_protocol_device(struct device_node *np, struct scmi_info *info,
 		return;
 	}
 
-	if (scmi_mbox_chan_setup(info, &sdev->dev, prot_id)) {
+	if (scmi_mbox_chan_setup(info, &sdev->dev, prot_id, true)) {
 		dev_err(&sdev->dev, "failed to setup transport\n");
 		scmi_device_destroy(sdev);
 		return;
@@ -741,7 +746,7 @@ static int scmi_probe(struct platform_device *pdev)
 	struct device_node *child, *np = dev->of_node;
 
 	/* Only mailbox method supported, check for the presence of one */
-	if (scmi_mailbox_check(np)) {
+	if (scmi_mailbox_check(np, 0)) {
 		dev_err(dev, "no mailbox found in %pOF\n", np);
 		return -EINVAL;
 	}
@@ -769,7 +774,7 @@ static int scmi_probe(struct platform_device *pdev)
 	handle->dev = info->dev;
 	handle->version = &info->version;
 
-	ret = scmi_mbox_chan_setup(info, dev, SCMI_PROTOCOL_BASE);
+	ret = scmi_mbox_chan_setup(info, dev, SCMI_PROTOCOL_BASE, true);
 	if (ret)
 		return ret;