1 files changed, 329 insertions, 0 deletions
diff --git a/drivers/firmware/arm_scmi/mailbox.c b/drivers/firmware/arm_scmi/mailbox.c
new file mode 100644
index 0000000000..b8d470417e
--- /dev/null
+++ b/drivers/firmware/arm_scmi/mailbox.c
@@ -0,0 +1,329 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * System Control and Management Interface (SCMI) Message Mailbox Transport
+ * driver.
+ *
+ * Copyright (C) 2019 ARM Ltd.
+ */
+
+#include <linux/err.h>
+#include <linux/device.h>
+#include <linux/mailbox_client.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/slab.h>
+
+#include "common.h"
+
+/**
+ * struct scmi_mailbox - Structure representing a SCMI mailbox transport
+ *
+ * @cl: Mailbox Client
+ * @chan: Transmit/Receive mailbox uni/bi-directional channel
+ * @chan_receiver: Optional Receiver mailbox unidirectional channel
+ * @cinfo: SCMI channel info
+ * @shmem: Transmit/Receive shared memory area
+ */
+struct scmi_mailbox {
+	struct mbox_client cl;
+	struct mbox_chan *chan;
+	struct mbox_chan *chan_receiver;
+	struct scmi_chan_info *cinfo;
+	struct scmi_shared_mem __iomem *shmem;
+};
+
+#define client_to_scmi_mailbox(c) container_of(c, struct scmi_mailbox, cl)
+
+static void tx_prepare(struct mbox_client *cl, void *m)
+{
+	struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
+
+	shmem_tx_prepare(smbox->shmem, m, smbox->cinfo);
+}
+
+static void rx_callback(struct mbox_client *cl, void *m)
+{
+	struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
+
+	/*
+	 * An A2P IRQ is NOT valid when received while the platform still has
+	 * the ownership of the channel, because the platform at first releases
+	 * the SMT channel and then sends the completion interrupt.
+	 *
+	 * This addresses a possible race condition in which a spurious IRQ from
+	 * a previous timed-out reply which arrived late could be wrongly
+	 * associated with the next pending transaction.
+	 */
+	if (cl->knows_txdone && !shmem_channel_free(smbox->shmem)) {
+		dev_warn(smbox->cinfo->dev, "Ignoring spurious A2P IRQ !\n");
+		return;
+	}
+
+	scmi_rx_callback(smbox->cinfo, shmem_read_header(smbox->shmem), NULL);
+}
+
+static bool mailbox_chan_available(struct device_node *of_node, int idx)
+{
+	int num_mb;
+
+	/*
+	 * Just check if bidirrectional channels are involved, and check the
+	 * index accordingly; proper full validation will be made later
+	 * in mailbox_chan_setup().
+	 */
+	num_mb = of_count_phandle_with_args(of_node, "mboxes", "#mbox-cells");
+	if (num_mb == 3 && idx == 1)
+		idx = 2;
+
+	return !of_parse_phandle_with_args(of_node, "mboxes",
+					   "#mbox-cells", idx, NULL);
+}
+
+/**
+ * mailbox_chan_validate  - Validate transport configuration and map channels
+ *
+ * @cdev: Reference to the underlying transport device carrying the
+ *	  of_node descriptor to analyze.
+ * @a2p_rx_chan: A reference to an optional unidirectional channel to use
+ *		 for replies on the a2p channel. Set as zero if not present.
+ * @p2a_chan: A reference to the optional p2a channel.
+ *	      Set as zero if not present.
+ *
+ * At first, validate the transport configuration as described in terms of
+ * 'mboxes' and 'shmem', then determin which mailbox channel indexes are
+ * appropriate to be use in the current configuration.
+ *
+ * Return: 0 on Success or error
+ */
+static int mailbox_chan_validate(struct device *cdev,
+				 int *a2p_rx_chan, int *p2a_chan)
+{
+	int num_mb, num_sh, ret = 0;
+	struct device_node *np = cdev->of_node;
+
+	num_mb = of_count_phandle_with_args(np, "mboxes", "#mbox-cells");
+	num_sh = of_count_phandle_with_args(np, "shmem", NULL);
+	dev_dbg(cdev, "Found %d mboxes and %d shmems !\n", num_mb, num_sh);
+
+	/* Bail out if mboxes and shmem descriptors are inconsistent */
+	if (num_mb <= 0 || num_sh <= 0 || num_sh > 2 || num_mb > 3 ||
+	    (num_mb == 1 && num_sh != 1) || (num_mb == 3 && num_sh != 2)) {
+		dev_warn(cdev,
+			 "Invalid channel descriptor for '%s' - mbs:%d  shm:%d\n",
+			 of_node_full_name(np), num_mb, num_sh);
+		return -EINVAL;
+	}
+
+	/* Bail out if provided shmem descriptors do not refer distinct areas  */
+	if (num_sh > 1) {
+		struct device_node *np_tx, *np_rx;
+
+		np_tx = of_parse_phandle(np, "shmem", 0);
+		np_rx = of_parse_phandle(np, "shmem", 1);
+		if (!np_tx || !np_rx || np_tx == np_rx) {
+			dev_warn(cdev, "Invalid shmem descriptor for '%s'\n",
+				 of_node_full_name(np));
+			ret = -EINVAL;
+		}
+
+		of_node_put(np_tx);
+		of_node_put(np_rx);
+	}
+
+	/* Calculate channels IDs to use depending on mboxes/shmem layout */
+	if (!ret) {
+		switch (num_mb) {
+		case 1:
+			*a2p_rx_chan = 0;
+			*p2a_chan = 0;
+			break;
+		case 2:
+			if (num_sh == 2) {
+				*a2p_rx_chan = 0;
+				*p2a_chan = 1;
+			} else {
+				*a2p_rx_chan = 1;
+				*p2a_chan = 0;
+			}
+			break;
+		case 3:
+			*a2p_rx_chan = 1;
+			*p2a_chan = 2;
+			break;
+		}
+	}
+
+	return ret;
+}
+
+static int mailbox_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
+			      bool tx)
+{
+	const char *desc = tx ? "Tx" : "Rx";
+	struct device *cdev = cinfo->dev;
+	struct scmi_mailbox *smbox;
+	struct device_node *shmem;
+	int ret, a2p_rx_chan, p2a_chan, idx = tx ? 0 : 1;
+	struct mbox_client *cl;
+	resource_size_t size;
+	struct resource res;
+
+	ret = mailbox_chan_validate(cdev, &a2p_rx_chan, &p2a_chan);
+	if (ret)
+		return ret;
+
+	if (!tx && !p2a_chan)
+		return -ENODEV;
+
+	smbox = devm_kzalloc(dev, sizeof(*smbox), GFP_KERNEL);
+	if (!smbox)
+		return -ENOMEM;
+
+	shmem = of_parse_phandle(cdev->of_node, "shmem", idx);
+	if (!of_device_is_compatible(shmem, "arm,scmi-shmem")) {
+		of_node_put(shmem);
+		return -ENXIO;
+	}
+
+	ret = of_address_to_resource(shmem, 0, &res);
+	of_node_put(shmem);
+	if (ret) {
+		dev_err(cdev, "failed to get SCMI %s shared memory\n", desc);
+		return ret;
+	}
+
+	size = resource_size(&res);
+	smbox->shmem = devm_ioremap(dev, res.start, size);
+	if (!smbox->shmem) {
+		dev_err(dev, "failed to ioremap SCMI %s shared memory\n", desc);
+		return -EADDRNOTAVAIL;
+	}
+
+	cl = &smbox->cl;
+	cl->dev = cdev;
+	cl->tx_prepare = tx ? tx_prepare : NULL;
+	cl->rx_callback = rx_callback;
+	cl->tx_block = false;
+	cl->knows_txdone = tx;
+
+	smbox->chan = mbox_request_channel(cl, tx ? 0 : p2a_chan);
+	if (IS_ERR(smbox->chan)) {
+		ret = PTR_ERR(smbox->chan);
+		if (ret != -EPROBE_DEFER)
+			dev_err(cdev,
+				"failed to request SCMI %s mailbox\n", desc);
+		return ret;
+	}
+
+	/* Additional unidirectional channel for TX if needed */
+	if (tx && a2p_rx_chan) {
+		smbox->chan_receiver = mbox_request_channel(cl, a2p_rx_chan);
+		if (IS_ERR(smbox->chan_receiver)) {
+			ret = PTR_ERR(smbox->chan_receiver);
+			if (ret != -EPROBE_DEFER)
+				dev_err(cdev, "failed to request SCMI Tx Receiver mailbox\n");
+			return ret;
+		}
+	}
+
+	cinfo->transport_info = smbox;
+	smbox->cinfo = cinfo;
+
+	return 0;
+}
+
+static int mailbox_chan_free(int id, void *p, void *data)
+{
+	struct scmi_chan_info *cinfo = p;
+	struct scmi_mailbox *smbox = cinfo->transport_info;
+
+	if (smbox && !IS_ERR(smbox->chan)) {
+		mbox_free_channel(smbox->chan);
+		mbox_free_channel(smbox->chan_receiver);
+		cinfo->transport_info = NULL;
+		smbox->chan = NULL;
+		smbox->chan_receiver = NULL;
+		smbox->cinfo = NULL;
+	}
+
+	return 0;
+}
+
+static int mailbox_send_message(struct scmi_chan_info *cinfo,
+				struct scmi_xfer *xfer)
+{
+	struct scmi_mailbox *smbox = cinfo->transport_info;
+	int ret;
+
+	ret = mbox_send_message(smbox->chan, xfer);
+
+	/* mbox_send_message returns non-negative value on success, so reset */
+	if (ret > 0)
+		ret = 0;
+
+	return ret;
+}
+
+static void mailbox_mark_txdone(struct scmi_chan_info *cinfo, int ret,
+				struct scmi_xfer *__unused)
+{
+	struct scmi_mailbox *smbox = cinfo->transport_info;
+
+	/*
+	 * NOTE: we might prefer not to need the mailbox ticker to manage the
+	 * transfer queueing since the protocol layer queues things by itself.
+	 * Unfortunately, we have to kick the mailbox framework after we have
+	 * received our message.
+	 */
+	mbox_client_txdone(smbox->chan, ret);
+}
+
+static void mailbox_fetch_response(struct scmi_chan_info *cinfo,
+				   struct scmi_xfer *xfer)
+{
+	struct scmi_mailbox *smbox = cinfo->transport_info;
+
+	shmem_fetch_response(smbox->shmem, xfer);
+}
+
+static void mailbox_fetch_notification(struct scmi_chan_info *cinfo,
+				       size_t max_len, struct scmi_xfer *xfer)
+{
+	struct scmi_mailbox *smbox = cinfo->transport_info;
+
+	shmem_fetch_notification(smbox->shmem, max_len, xfer);
+}
+
+static void mailbox_clear_channel(struct scmi_chan_info *cinfo)
+{
+	struct scmi_mailbox *smbox = cinfo->transport_info;
+
+	shmem_clear_channel(smbox->shmem);
+}
+
+static bool
+mailbox_poll_done(struct scmi_chan_info *cinfo, struct scmi_xfer *xfer)
+{
+	struct scmi_mailbox *smbox = cinfo->transport_info;
+
+	return shmem_poll_done(smbox->shmem, xfer);
+}
+
+static const struct scmi_transport_ops scmi_mailbox_ops = {
+	.chan_available = mailbox_chan_available,
+	.chan_setup = mailbox_chan_setup,
+	.chan_free = mailbox_chan_free,
+	.send_message = mailbox_send_message,
+	.mark_txdone = mailbox_mark_txdone,
+	.fetch_response = mailbox_fetch_response,
+	.fetch_notification = mailbox_fetch_notification,
+	.clear_channel = mailbox_clear_channel,
+	.poll_done = mailbox_poll_done,
+};
+
+const struct scmi_desc scmi_mailbox_desc = {
+	.ops = &scmi_mailbox_ops,
+	.max_rx_timeout_ms = 30, /* We may increase this if required */
+	.max_msg = 20, /* Limited by MBOX_TX_QUEUE_LEN */
+	.max_msg_size = 128,
+};