[PATCH v5 8/8] firmware: arm_scpi: Support unidirectional mailbox channels

[Samuel Holland <samuel@xxxxxxxxxxxx>]

Some mailbox controllers have only unidirectional channels, so we need a
pair of them for each SCPI channel. If a mbox-names property is present,
look for "rx" and "tx" mbox channels; otherwise, the existing behavior
is preserved, and a single mbox channel is used for each SCPI channel.

Note that since the mailbox framework only supports a single phandle
with each name (mbox_request_channel_byname always returns the first
one), this new mode only supports a single SCPI channel.

Signed-off-by: Samuel Holland <samuel@xxxxxxxxxxxx>
---
 drivers/firmware/arm_scpi.c | 58 +++++++++++++++++++++++++++++--------
 1 file changed, 46 insertions(+), 12 deletions(-)

diff --git a/drivers/firmware/arm_scpi.c b/drivers/firmware/arm_scpi.c
index a80c331c3a6e..36ff9dd8d0fa 100644
--- a/drivers/firmware/arm_scpi.c
+++ b/drivers/firmware/arm_scpi.c
@@ -231,7 +231,8 @@ struct scpi_xfer {
 
 struct scpi_chan {
 	struct mbox_client cl;
-	struct mbox_chan *chan;
+	struct mbox_chan *rx_chan;
+	struct mbox_chan *tx_chan;
 	void __iomem *tx_payload;
 	void __iomem *rx_payload;
 	struct list_head rx_pending;
@@ -505,7 +506,7 @@ static int scpi_send_message(u8 idx, void *tx_buf, unsigned int tx_len,
 	msg->rx_len = rx_len;
 	reinit_completion(&msg->done);
 
-	ret = mbox_send_message(scpi_chan->chan, msg);
+	ret = mbox_send_message(scpi_chan->tx_chan, msg);
 	if (ret < 0 || !rx_buf)
 		goto out;
 
@@ -854,8 +855,13 @@ static void scpi_free_channels(void *data)
 	struct scpi_drvinfo *info = data;
 	int i;
 
-	for (i = 0; i < info->num_chans; i++)
-		mbox_free_channel(info->channels[i].chan);
+	for (i = 0; i < info->num_chans; i++) {
+		struct scpi_chan *pchan = &info->channels[i];
+
+		if (pchan->tx_chan != pchan->rx_chan)
+			mbox_free_channel(pchan->tx_chan);
+		mbox_free_channel(pchan->rx_chan);
+	}
 }
 
 static int scpi_remove(struct platform_device *pdev)
@@ -903,6 +909,7 @@ static int scpi_probe(struct platform_device *pdev)
 	struct resource res;
 	struct device *dev = &pdev->dev;
 	struct device_node *np = dev->of_node;
+	bool use_mbox_names = false;
 
 	scpi_info = devm_kzalloc(dev, sizeof(*scpi_info), GFP_KERNEL);
 	if (!scpi_info)
@@ -916,6 +923,14 @@ static int scpi_probe(struct platform_device *pdev)
 		dev_err(dev, "no mboxes property in '%pOF'\n", np);
 		return -ENODEV;
 	}
+	if (of_get_property(dev->of_node, "mbox-names", NULL)) {
+		use_mbox_names = true;
+		if (count != 2) {
+			dev_err(dev, "need exactly 2 mboxes with mbox-names\n");
+			return -ENODEV;
+		}
+		count /= 2;
+	}
 
 	scpi_info->channels = devm_kcalloc(dev, count, sizeof(struct scpi_chan),
 					   GFP_KERNEL);
@@ -961,15 +976,34 @@ static int scpi_probe(struct platform_device *pdev)
 		mutex_init(&pchan->xfers_lock);
 
 		ret = scpi_alloc_xfer_list(dev, pchan);
-		if (!ret) {
-			pchan->chan = mbox_request_channel(cl, idx);
-			if (!IS_ERR(pchan->chan))
-				continue;
-			ret = PTR_ERR(pchan->chan);
-			if (ret != -EPROBE_DEFER)
-				dev_err(dev, "failed to get channel%d err %d\n",
-					idx, ret);
+		if (ret)
+			return ret;
+
+		if (use_mbox_names) {
+			pchan->rx_chan = mbox_request_channel_byname(cl, "rx");
+			if (IS_ERR(pchan->rx_chan)) {
+				ret = PTR_ERR(pchan->rx_chan);
+				goto fail;
+			}
+			pchan->tx_chan = mbox_request_channel_byname(cl, "tx");
+			if (IS_ERR(pchan->rx_chan)) {
+				ret = PTR_ERR(pchan->tx_chan);
+				goto fail;
+			}
+		} else {
+			pchan->rx_chan = mbox_request_channel(cl, idx);
+			if (IS_ERR(pchan->rx_chan)) {
+				ret = PTR_ERR(pchan->rx_chan);
+				goto fail;
+			}
+			pchan->tx_chan = pchan->rx_chan;
 		}
+		continue;
+
+fail:
+		if (ret != -EPROBE_DEFER)
+			dev_err(dev, "failed to get channel%d err %d\n",
+				idx, ret);
 		return ret;
 	}
 
-- 
2.23.0