[PATCH] firmware: arm_scmi: Make scmi core independent of transport type

[Viresh Kumar <viresh.kumar@linaro.org>]

The SCMI specification is fairly independent of the transport protocol,
which can be a simple mailbox (already implemented) or anything else.
The current Linux implementation however is very much dependent of the
mailbox transport layer.

This patch makes the SCMI core code (driver.c) independent of the
mailbox transport layer and moves all mailbox related code to a new
file: mailbox.c.

We can now implement more transport protocols to transport SCMI
messages.

The transport protocols just need to provide struct scmi_transport_ops,
with its version of the callbacks to enable exchange of SCMI messages.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
 drivers/firmware/arm_scmi/Makefile  |   3 +-
 drivers/firmware/arm_scmi/common.h  |  39 ++++++++
 drivers/firmware/arm_scmi/driver.c  | 143 ++++++++++-----------------
 drivers/firmware/arm_scmi/mailbox.c | 146 ++++++++++++++++++++++++++++
 4 files changed, 236 insertions(+), 95 deletions(-)
 create mode 100644 drivers/firmware/arm_scmi/mailbox.c

diff --git a/drivers/firmware/arm_scmi/Makefile b/drivers/firmware/arm_scmi/Makefile
index 5f298f00a82e..df2c05a545d8 100644
--- a/drivers/firmware/arm_scmi/Makefile
+++ b/drivers/firmware/arm_scmi/Makefile
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0-only
-obj-y	= scmi-bus.o scmi-driver.o scmi-protocols.o
+obj-y	= scmi-bus.o scmi-driver.o scmi-protocols.o scmi-transport.o
 scmi-bus-y = bus.o
 scmi-driver-y = driver.o
+scmi-transport-y = mailbox.o
 scmi-protocols-y = base.o clock.o perf.o power.o reset.o sensors.o
 obj-$(CONFIG_ARM_SCMI_POWER_DOMAIN) += scmi_pm_domain.o
diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
index 5237c2ff79fe..e11314146e67 100644
--- a/drivers/firmware/arm_scmi/common.h
+++ b/drivers/firmware/arm_scmi/common.h
@@ -111,3 +111,42 @@ void scmi_setup_protocol_implemented(const struct scmi_handle *handle,
 				     u8 *prot_imp);
 
 int scmi_base_protocol_init(struct scmi_handle *h);
+
+/* SCMI Transport */
+
+/**
+ * struct scmi_chan_info - Structure representing a SCMI channel information
+ *
+ * @payload: Transmit/Receive payload area
+ * @dev: Reference to device in the SCMI hierarchy corresponding to this
+ *	 channel
+ * @handle: Pointer to SCMI entity handle
+ * @transport_info: Transport layer related information
+ */
+struct scmi_chan_info {
+	void __iomem *payload;
+	struct device *dev;
+	struct scmi_handle *handle;
+	void *transport_info;
+};
+
+/**
+ * struct scmi_transport_ops - Structure representing a SCMI transport ops
+ *
+ * @send_message: Callback to send a message
+ * @mark_txdone: Callback to mark tx as done
+ * @chan_setup: Callback to allocate and setup a channel
+ * @chan_free: Callback to free a channel
+ */
+struct scmi_transport_ops {
+	bool (*chan_available)(struct device *dev, int idx);
+	int (*chan_setup)(struct scmi_chan_info *cinfo, bool tx);
+	int (*chan_free)(int id, void *p, void *data);
+	int (*send_message)(struct scmi_chan_info *cinfo, struct scmi_xfer *xfer);
+	void (*mark_txdone)(struct scmi_chan_info *cinfo, int ret);
+};
+
+void scmi_tx_prepare(struct scmi_chan_info *cinfo, struct scmi_xfer *t);
+void scmi_rx_callback(struct scmi_chan_info *cinfo, struct scmi_xfer *t);
+void scmi_free_channel(struct scmi_chan_info *cinfo, struct idr *idr, int id);
+struct scmi_transport_ops *scmi_mailbox_get_ops(struct device *dev);
diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 3eb0382491ce..dfdd12f3dd8b 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -19,7 +19,6 @@
 #include <linux/io.h>
 #include <linux/kernel.h>
 #include <linux/ktime.h>
-#include <linux/mailbox_client.h>
 #include <linux/module.h>
 #include <linux/of_address.h>
 #include <linux/of_device.h>
@@ -91,24 +90,6 @@ struct scmi_desc {
 	int max_msg_size;
 };
 
-/**
- * struct scmi_chan_info - Structure representing a SCMI channel information
- *
- * @cl: Mailbox Client
- * @chan: Transmit/Receive mailbox channel
- * @payload: Transmit/Receive mailbox channel payload area
- * @dev: Reference to device in the SCMI hierarchy corresponding to this
- *	 channel
- * @handle: Pointer to SCMI entity handle
- */
-struct scmi_chan_info {
-	struct mbox_client cl;
-	struct mbox_chan *chan;
-	void __iomem *payload;
-	struct device *dev;
-	struct scmi_handle *handle;
-};
-
 /**
  * struct scmi_info - Structure representing a SCMI instance
  *
@@ -128,6 +109,7 @@ struct scmi_chan_info {
 struct scmi_info {
 	struct device *dev;
 	const struct scmi_desc *desc;
+	struct scmi_transport_ops *transport_ops;
 	struct scmi_revision_info version;
 	struct scmi_handle handle;
 	struct scmi_xfers_info tx_minfo;
@@ -138,7 +120,6 @@ struct scmi_info {
 	int users;
 };
 
-#define client_to_scmi_chan_info(c) container_of(c, struct scmi_chan_info, cl)
 #define handle_to_scmi_info(h)	container_of(h, struct scmi_info, handle)
 
 /*
@@ -233,18 +214,16 @@ static inline void unpack_scmi_header(u32 msg_hdr, struct scmi_msg_hdr *hdr)
 }
 
 /**
- * scmi_tx_prepare() - mailbox client callback to prepare for the transfer
+ * scmi_tx_prepare() - callback to prepare for the transfer
  *
- * @cl: client pointer
- * @m: mailbox message
+ * @cinfo: SCMI channel info
+ * @t: transfer message
  *
  * This function prepares the shared memory which contains the header and the
  * payload.
  */
-static void scmi_tx_prepare(struct mbox_client *cl, void *m)
+void scmi_tx_prepare(struct scmi_chan_info *cinfo, struct scmi_xfer *t)
 {
-	struct scmi_xfer *t = m;
-	struct scmi_chan_info *cinfo = client_to_scmi_chan_info(cl);
 	struct scmi_shared_mem __iomem *mem = cinfo->payload;
 
 	/*
@@ -332,10 +311,10 @@ __scmi_xfer_put(struct scmi_xfers_info *minfo, struct scmi_xfer *xfer)
 }
 
 /**
- * scmi_rx_callback() - mailbox client callback for receive messages
+ * scmi_rx_callback() - callback for receive messages
  *
- * @cl: client pointer
- * @m: mailbox message
+ * @cinfo: SCMI channel info
+ * @t: transfer message
  *
  * Processes one received message to appropriate transfer information and
  * signals completion of the transfer.
@@ -343,13 +322,12 @@ __scmi_xfer_put(struct scmi_xfers_info *minfo, struct scmi_xfer *xfer)
  * NOTE: This function will be invoked in IRQ context, hence should be
  * as optimal as possible.
  */
-static void scmi_rx_callback(struct mbox_client *cl, void *m)
+void scmi_rx_callback(struct scmi_chan_info *cinfo, struct scmi_xfer *t)
 {
 	u8 msg_type;
 	u32 msg_hdr;
 	u16 xfer_id;
 	struct scmi_xfer *xfer;
-	struct scmi_chan_info *cinfo = client_to_scmi_chan_info(cl);
 	struct device *dev = cinfo->dev;
 	struct scmi_info *info = handle_to_scmi_info(cinfo->handle);
 	struct scmi_xfers_info *minfo = &info->tx_minfo;
@@ -439,15 +417,12 @@ int scmi_do_xfer(const struct scmi_handle *handle, struct scmi_xfer *xfer)
 	if (unlikely(!cinfo))
 		return -EINVAL;
 
-	ret = mbox_send_message(cinfo->chan, xfer);
+	ret = info->transport_ops->send_message(cinfo, xfer);
 	if (ret < 0) {
-		dev_dbg(dev, "mbox send fail %d\n", ret);
+		dev_dbg(dev, "Failed to send message %d\n", ret);
 		return ret;
 	}
 
-	/* mbox_send_message returns non-negative value on success, so reset */
-	ret = 0;
-
 	if (xfer->hdr.poll_completion) {
 		ktime_t stop = ktime_add_ns(ktime_get(), SCMI_MAX_POLL_TO_NS);
 
@@ -461,7 +436,7 @@ int scmi_do_xfer(const struct scmi_handle *handle, struct scmi_xfer *xfer)
 		/* And we wait for the response. */
 		timeout = msecs_to_jiffies(info->desc->max_rx_timeout_ms);
 		if (!wait_for_completion_timeout(&xfer->done, timeout)) {
-			dev_err(dev, "mbox timed out in resp(caller: %pS)\n",
+			dev_err(dev, "timed out in resp(caller: %pS)\n",
 				(void *)_RET_IP_);
 			ret = -ETIMEDOUT;
 		}
@@ -470,13 +445,7 @@ int scmi_do_xfer(const struct scmi_handle *handle, struct scmi_xfer *xfer)
 	if (!ret && xfer->hdr.status)
 		ret = scmi_to_linux_errno(xfer->hdr.status);
 
-	/*
-	 * 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(cinfo->chan, ret);
+	info->transport_ops->mark_txdone(cinfo, ret);
 
 	return ret;
 }
@@ -713,21 +682,14 @@ static int scmi_xfer_info_init(struct scmi_info *sinfo)
 	return 0;
 }
 
-static int scmi_mailbox_check(struct device_node *np, int idx)
-{
-	return of_parse_phandle_with_args(np, "mboxes", "#mbox-cells",
-					  idx, NULL);
-}
-
-static int scmi_mbox_chan_setup(struct scmi_info *info, struct device *dev,
-				int prot_id, bool tx)
+static int scmi_chan_setup(struct scmi_info *info, struct device *dev,
+			   int prot_id, bool tx)
 {
 	int ret, idx;
 	struct resource res;
 	resource_size_t size;
-	struct device_node *shmem, *np = dev->of_node;
+	struct device_node *shmem;
 	struct scmi_chan_info *cinfo;
-	struct mbox_client *cl;
 	struct idr *idr;
 	const char *desc = tx ? "Tx" : "Rx";
 
@@ -735,7 +697,7 @@ static int scmi_mbox_chan_setup(struct scmi_info *info, struct device *dev,
 	idx = tx ? 0 : 1;
 	idr = tx ? &info->tx_idr : &info->rx_idr;
 
-	if (scmi_mailbox_check(np, idx)) {
+	if (!info->transport_ops->chan_available(dev, idx)) {
 		cinfo = idr_find(idr, SCMI_PROTOCOL_BASE);
 		if (unlikely(!cinfo)) /* Possible only if platform has no Rx */
 			return -EINVAL;
@@ -748,14 +710,7 @@ static int scmi_mbox_chan_setup(struct scmi_info *info, struct device *dev,
 
 	cinfo->dev = dev;
 
-	cl = &cinfo->cl;
-	cl->dev = dev;
-	cl->rx_callback = scmi_rx_callback;
-	cl->tx_prepare = tx ? scmi_tx_prepare : NULL;
-	cl->tx_block = false;
-	cl->knows_txdone = tx;
-
-	shmem = of_parse_phandle(np, "shmem", idx);
+	shmem = of_parse_phandle(dev->of_node, "shmem", idx);
 	ret = of_address_to_resource(shmem, 0, &res);
 	of_node_put(shmem);
 	if (ret) {
@@ -770,14 +725,9 @@ static int scmi_mbox_chan_setup(struct scmi_info *info, struct device *dev,
 		return -EADDRNOTAVAIL;
 	}
 
-	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 %s mailbox\n",
-				desc);
+	ret = info->transport_ops->chan_setup(cinfo, tx);
+	if (ret)
 		return ret;
-	}
 
 idr_alloc:
 	ret = idr_alloc(idr, cinfo, prot_id, prot_id + 1, GFP_KERNEL);
@@ -791,12 +741,12 @@ static int scmi_mbox_chan_setup(struct scmi_info *info, struct device *dev,
 }
 
 static inline int
-scmi_mbox_txrx_setup(struct scmi_info *info, struct device *dev, int prot_id)
+scmi_txrx_setup(struct scmi_info *info, struct device *dev, int prot_id)
 {
-	int ret = scmi_mbox_chan_setup(info, dev, prot_id, true);
+	int ret = scmi_chan_setup(info, dev, prot_id, true);
 
 	if (!ret) /* Rx is optional, hence no error check */
-		scmi_mbox_chan_setup(info, dev, prot_id, false);
+		scmi_chan_setup(info, dev, prot_id, false);
 
 	return ret;
 }
@@ -814,7 +764,7 @@ scmi_create_protocol_device(struct device_node *np, struct scmi_info *info,
 		return;
 	}
 
-	if (scmi_mbox_txrx_setup(info, &sdev->dev, prot_id)) {
+	if (scmi_txrx_setup(info, &sdev->dev, prot_id)) {
 		dev_err(&sdev->dev, "failed to setup transport\n");
 		scmi_device_destroy(sdev);
 		return;
@@ -824,6 +774,23 @@ scmi_create_protocol_device(struct device_node *np, struct scmi_info *info,
 	scmi_set_handle(sdev);
 }
 
+static int scmi_set_transport_ops(struct scmi_info *info)
+{
+	struct scmi_transport_ops *ops;
+	struct device *dev = info->dev;
+
+	/* Only mailbox method supported for now */
+	ops = scmi_mailbox_get_ops(dev);
+	if (!ops) {
+		dev_err(dev, "Transport protocol not found in %pOF\n",
+			dev->of_node);
+		return -EINVAL;
+	}
+
+	info->transport_ops = ops;
+	return 0;
+}
+
 static int scmi_probe(struct platform_device *pdev)
 {
 	int ret;
@@ -833,12 +800,6 @@ static int scmi_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct device_node *child, *np = dev->of_node;
 
-	/* Only mailbox method supported, check for the presence of one */
-	if (scmi_mailbox_check(np, 0)) {
-		dev_err(dev, "no mailbox found in %pOF\n", np);
-		return -EINVAL;
-	}
-
 	desc = of_device_get_match_data(dev);
 	if (!desc)
 		return -EINVAL;
@@ -851,6 +812,10 @@ static int scmi_probe(struct platform_device *pdev)
 	info->desc = desc;
 	INIT_LIST_HEAD(&info->node);
 
+	ret = scmi_set_transport_ops(info);
+	if (ret)
+		return ret;
+
 	ret = scmi_xfer_info_init(info);
 	if (ret)
 		return ret;
@@ -863,7 +828,7 @@ static int scmi_probe(struct platform_device *pdev)
 	handle->dev = info->dev;
 	handle->version = &info->version;
 
-	ret = scmi_mbox_txrx_setup(info, dev, SCMI_PROTOCOL_BASE);
+	ret = scmi_txrx_setup(info, dev, SCMI_PROTOCOL_BASE);
 	if (ret)
 		return ret;
 
@@ -898,19 +863,9 @@ static int scmi_probe(struct platform_device *pdev)
 	return 0;
 }
 
-static int scmi_mbox_free_channel(int id, void *p, void *data)
+void scmi_free_channel(struct scmi_chan_info *cinfo, struct idr *idr, int id)
 {
-	struct scmi_chan_info *cinfo = p;
-	struct idr *idr = data;
-
-	if (!IS_ERR_OR_NULL(cinfo->chan)) {
-		mbox_free_channel(cinfo->chan);
-		cinfo->chan = NULL;
-	}
-
 	idr_remove(idr, id);
-
-	return 0;
 }
 
 static int scmi_remove(struct platform_device *pdev)
@@ -930,11 +885,11 @@ static int scmi_remove(struct platform_device *pdev)
 		return ret;
 
 	/* Safe to free channels since no more users */
-	ret = idr_for_each(idr, scmi_mbox_free_channel, idr);
+	ret = idr_for_each(idr, info->transport_ops->chan_free, idr);
 	idr_destroy(&info->tx_idr);
 
 	idr = &info->rx_idr;
-	ret = idr_for_each(idr, scmi_mbox_free_channel, idr);
+	ret = idr_for_each(idr, info->transport_ops->chan_free, idr);
 	idr_destroy(&info->rx_idr);
 
 	return ret;
diff --git a/drivers/firmware/arm_scmi/mailbox.c b/drivers/firmware/arm_scmi/mailbox.c
new file mode 100644
index 000000000000..d9d301df5cc9
--- /dev/null
+++ b/drivers/firmware/arm_scmi/mailbox.c
@@ -0,0 +1,146 @@
+// 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/slab.h>
+
+#include "common.h"
+
+/**
+ * struct scmi_mailbox - Structure representing a SCMI mailbox transport
+ *
+ * @cl: Mailbox Client
+ * @chan: Transmit/Receive mailbox channel
+ * @cinfo: SCMI channel info
+ */
+struct scmi_mailbox {
+	struct mbox_client cl;
+	struct mbox_chan *chan;
+	struct scmi_chan_info *cinfo;
+};
+
+#define client_to_scmi_mailbox(c) container_of(c, struct scmi_mailbox, cl)
+
+static bool mailbox_chan_available(struct device *dev, int idx)
+{
+	return !of_parse_phandle_with_args(dev->of_node, "mboxes",
+					   "#mbox-cells", idx, NULL);
+}
+
+static void mailbox_tx_prepare(struct mbox_client *cl, void *m)
+{
+	struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
+	struct scmi_chan_info *cinfo = smbox->cinfo;
+
+	scmi_tx_prepare(cinfo, m);
+}
+
+static void mailbox_rx_callback(struct mbox_client *cl, void *m)
+{
+	struct scmi_mailbox *smbox = client_to_scmi_mailbox(cl);
+	struct scmi_chan_info *cinfo = smbox->cinfo;
+
+	scmi_rx_callback(cinfo, m);
+}
+
+static int mailbox_chan_setup(struct scmi_chan_info *cinfo, bool tx)
+{
+	struct device *dev = cinfo->dev;
+	struct scmi_mailbox *smbox;
+	struct mbox_client *cl;
+	int ret;
+
+	smbox = devm_kzalloc(dev, sizeof(*smbox), GFP_KERNEL);
+	if (!smbox)
+		return -ENOMEM;
+
+	cl = &smbox->cl;
+	cl->dev = dev;
+	cl->tx_prepare = tx ? mailbox_tx_prepare : NULL;
+	cl->rx_callback = mailbox_rx_callback;
+	cl->tx_block = false;
+	cl->knows_txdone = tx;
+
+	smbox->chan = mbox_request_channel(cl, tx ? 0 : 1);
+	if (IS_ERR(smbox->chan)) {
+		ret = PTR_ERR(smbox->chan);
+		if (ret != -EPROBE_DEFER)
+			dev_err(dev, "failed to request SCMI %s mailbox\n",
+				tx ? "Tx" : "Rx");
+		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 (!IS_ERR_OR_NULL(smbox->chan)) {
+		mbox_free_channel(smbox->chan);
+		cinfo->transport_info = NULL;
+		smbox->chan = NULL;
+		smbox->cinfo = NULL;
+	}
+
+	scmi_free_channel(cinfo, data, id);
+
+	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_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 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,
+};
+
+struct scmi_transport_ops *scmi_mailbox_get_ops(struct device *dev)
+{
+	if (!of_parse_phandle_with_args(dev->of_node, "mboxes", "#mbox-cells",
+					0, NULL))
+		return &scmi_mailbox_ops;
+
+	return NULL;
+}
-- 
2.21.0.rc0.269.g1a574e7a288b