Merge tag 'scmi-updates-5.8' of...

Merge tag 'scmi-updates-5.8' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux into arm/drivers

ARM SCMI/SCPI updates for v5.8

1. Addition of ARM SMC/HVC as SCMI transport type with required
   abstraction already in place
2. Initial infrastructure support to add SCMI notifications from
   platform to agents
3. Miscellaneous fix adding header include guards

* tag 'scmi-updates-5.8' of git://git.kernel.org/pub/scm/linux/kernel/git/sudeep.holla/linux:
  firmware: arm_scmi: fix psci dependency
  firmware: arm_scmi: Fix return error code in smc_send_message
  firmware: arm_scmi: Fix handling of unexpected delayed responses
  firmware: arm_scmi: Clear channel for delayed responses
  firmware: arm_scmi: Clear channel on reception of unexpected responses
  firmware: arm_scmi: Rename .clear_notification() transport_ops
  firmware: arm_scmi: Add support for notifications message processing
  firmware: arm_scmi: Add notifications support in transport layer
  firmware: arm_scmi: Update protocol commands and notification list
  firmware: arm_scmi: Add receive buffer support for notifications
  firmware: arm_scpi: Add include guard to linux/scpi_protocol.h
  firmware: arm_scmi: Add include guard to linux/scmi_protocol.h
  firmware: arm_scmi: Drop checking for shmem property in parent node
  firmware: arm_scmi: Check shmem property for channel availablity
  firmware: arm_scmi: Drop empty stub for smc_mark_txdone
  firmware: arm_scmi: Make mutex channel specific
  firmware: arm_scmi: Add smc/hvc transport
  dt-bindings: arm: Add smc/hvc transport for SCMI

Link: https://lore.kernel.org/r/20200512110357.GA26454@bogusSigned-off-by: Arnd Bergmann <arnd@arndb.de>

Documentation/devicetree/bindings/arm/arm,scmi.txt

@@ -14,7 +14,7 @@ Required properties:
 
 The scmi node with the following properties shall be under the /firmware/ node.
 
-- compatible : shall be "arm,scmi"
+- compatible : shall be "arm,scmi" or "arm,scmi-smc" for smc/hvc transports
 - mboxes: List of phandle and mailbox channel specifiers. It should contain
 	  exactly one or two mailboxes, one for transmitting messages("tx")
 	  and another optional for receiving the notifications("rx") if
@@ -25,6 +25,7 @@ The scmi node with the following properties shall be under the /firmware/ node.
 	  protocol identifier for a given sub-node.
 - #size-cells : should be '0' as 'reg' property doesn't have any size
 	  associated with it.
+- arm,smc-id : SMC id required when using smc or hvc transports
 
 Optional properties:
 

drivers/firmware/arm_scmi/Makefile

@@ -2,6 +2,8 @@
 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 shmem.o
+scmi-transport-y = shmem.o
+scmi-transport-$(CONFIG_MAILBOX) += mailbox.o
+scmi-transport-$(CONFIG_ARM_PSCI_FW) += smc.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

drivers/firmware/arm_scmi/base.c

@@ -14,6 +14,13 @@ enum scmi_base_protocol_cmd {
 	BASE_DISCOVER_LIST_PROTOCOLS = 0x6,
 	BASE_DISCOVER_AGENT = 0x7,
 	BASE_NOTIFY_ERRORS = 0x8,
+	BASE_SET_DEVICE_PERMISSIONS = 0x9,
+	BASE_SET_PROTOCOL_PERMISSIONS = 0xa,
+	BASE_RESET_AGENT_CONFIGURATION = 0xb,
+};
+
+enum scmi_base_protocol_notify {
+	BASE_ERROR_EVENT = 0x0,
 };
 
 struct scmi_msg_resp_base_attributes {

drivers/firmware/arm_scmi/common.h

@@ -178,6 +178,8 @@ struct scmi_chan_info {
  * @send_message: Callback to send a message
  * @mark_txdone: Callback to mark tx as done
  * @fetch_response: Callback to fetch response
+ * @fetch_notification: Callback to fetch notification
+ * @clear_channel: Callback to clear a channel
  * @poll_done: Callback to poll transfer status
  */
 struct scmi_transport_ops {
@@ -190,6 +192,9 @@ struct scmi_transport_ops {
 	void (*mark_txdone)(struct scmi_chan_info *cinfo, int ret);
 	void (*fetch_response)(struct scmi_chan_info *cinfo,
 			       struct scmi_xfer *xfer);
+	void (*fetch_notification)(struct scmi_chan_info *cinfo,
+				   size_t max_len, struct scmi_xfer *xfer);
+	void (*clear_channel)(struct scmi_chan_info *cinfo);
 	bool (*poll_done)(struct scmi_chan_info *cinfo, struct scmi_xfer *xfer);
 };
 
@@ -210,6 +215,9 @@ struct scmi_desc {
 };
 
 extern const struct scmi_desc scmi_mailbox_desc;
+#ifdef CONFIG_HAVE_ARM_SMCCC
+extern const struct scmi_desc scmi_smc_desc;
+#endif
 
 void scmi_rx_callback(struct scmi_chan_info *cinfo, u32 msg_hdr);
 void scmi_free_channel(struct scmi_chan_info *cinfo, struct idr *idr, int id);
@@ -222,5 +230,8 @@ void shmem_tx_prepare(struct scmi_shared_mem __iomem *shmem,
 u32 shmem_read_header(struct scmi_shared_mem __iomem *shmem);
 void shmem_fetch_response(struct scmi_shared_mem __iomem *shmem,
 			  struct scmi_xfer *xfer);
+void shmem_fetch_notification(struct scmi_shared_mem __iomem *shmem,
+			      size_t max_len, struct scmi_xfer *xfer);
+void shmem_clear_channel(struct scmi_shared_mem __iomem *shmem);
 bool shmem_poll_done(struct scmi_shared_mem __iomem *shmem,
 		     struct scmi_xfer *xfer);

drivers/firmware/arm_scmi/driver.c

@@ -76,6 +76,7 @@ struct scmi_xfers_info {
  *	implementation version and (sub-)vendor identification.
  * @handle: Instance of SCMI handle to send to clients
  * @tx_minfo: Universal Transmit Message management info
+ * @rx_minfo: Universal Receive Message management info
  * @tx_idr: IDR object to map protocol id to Tx channel info pointer
  * @rx_idr: IDR object to map protocol id to Rx channel info pointer
  * @protocols_imp: List of protocols implemented, currently maximum of
@@ -89,6 +90,7 @@ struct scmi_info {
 	struct scmi_revision_info version;
 	struct scmi_handle handle;
 	struct scmi_xfers_info tx_minfo;
+	struct scmi_xfers_info rx_minfo;
 	struct idr tx_idr;
 	struct idr rx_idr;
 	u8 *protocols_imp;
@@ -200,37 +202,66 @@ __scmi_xfer_put(struct scmi_xfers_info *minfo, struct scmi_xfer *xfer)
 	spin_unlock_irqrestore(&minfo->xfer_lock, flags);
 }
 
-/**
- * scmi_rx_callback() - callback for receiving messages
- *
- * @cinfo: SCMI channel info
- * @msg_hdr: Message header
- *
- * Processes one received message to appropriate transfer information and
- * signals completion of the transfer.
- *
- * NOTE: This function will be invoked in IRQ context, hence should be
- * as optimal as possible.
- */
-void scmi_rx_callback(struct scmi_chan_info *cinfo, u32 msg_hdr)
+static void scmi_handle_notification(struct scmi_chan_info *cinfo, u32 msg_hdr)
 {
-	struct scmi_info *info = handle_to_scmi_info(cinfo->handle);
-	struct scmi_xfers_info *minfo = &info->tx_minfo;
-	u16 xfer_id = MSG_XTRACT_TOKEN(msg_hdr);
-	u8 msg_type = MSG_XTRACT_TYPE(msg_hdr);
-	struct device *dev = cinfo->dev;
 	struct scmi_xfer *xfer;
+	struct device *dev = cinfo->dev;
+	struct scmi_info *info = handle_to_scmi_info(cinfo->handle);
+	struct scmi_xfers_info *minfo = &info->rx_minfo;
+
+	xfer = scmi_xfer_get(cinfo->handle, minfo);
+	if (IS_ERR(xfer)) {
+		dev_err(dev, "failed to get free message slot (%ld)\n",
+			PTR_ERR(xfer));
+		info->desc->ops->clear_channel(cinfo);
+		return;
+	}
 
-	if (msg_type == MSG_TYPE_NOTIFICATION)
-		return; /* Notifications not yet supported */
+	unpack_scmi_header(msg_hdr, &xfer->hdr);
+	scmi_dump_header_dbg(dev, &xfer->hdr);
+	info->desc->ops->fetch_notification(cinfo, info->desc->max_msg_size,
+					    xfer);
+
+	trace_scmi_rx_done(xfer->transfer_id, xfer->hdr.id,
+			   xfer->hdr.protocol_id, xfer->hdr.seq,
+			   MSG_TYPE_NOTIFICATION);
+
+	__scmi_xfer_put(minfo, xfer);
+
+	info->desc->ops->clear_channel(cinfo);
+}
+
+static void scmi_handle_response(struct scmi_chan_info *cinfo,
+				 u16 xfer_id, u8 msg_type)
+{
+	struct scmi_xfer *xfer;
+	struct device *dev = cinfo->dev;
+	struct scmi_info *info = handle_to_scmi_info(cinfo->handle);
+	struct scmi_xfers_info *minfo = &info->tx_minfo;
 
 	/* Are we even expecting this? */
 	if (!test_bit(xfer_id, minfo->xfer_alloc_table)) {
 		dev_err(dev, "message for %d is not expected!\n", xfer_id);
+		info->desc->ops->clear_channel(cinfo);
 		return;
 	}
 
 	xfer = &minfo->xfer_block[xfer_id];
+	/*
+	 * Even if a response was indeed expected on this slot at this point,
+	 * a buggy platform could wrongly reply feeding us an unexpected
+	 * delayed response we're not prepared to handle: bail-out safely
+	 * blaming firmware.
+	 */
+	if (unlikely(msg_type == MSG_TYPE_DELAYED_RESP && !xfer->async_done)) {
+		dev_err(dev,
+			"Delayed Response for %d not expected! Buggy F/W ?\n",
+			xfer_id);
+		info->desc->ops->clear_channel(cinfo);
+		/* It was unexpected, so nobody will clear the xfer if not us */
+		__scmi_xfer_put(minfo, xfer);
+		return;
+	}
 
 	scmi_dump_header_dbg(dev, &xfer->hdr);
 
@@ -240,10 +271,43 @@ void scmi_rx_callback(struct scmi_chan_info *cinfo, u32 msg_hdr)
 			   xfer->hdr.protocol_id, xfer->hdr.seq,
 			   msg_type);
 
-	if (msg_type == MSG_TYPE_DELAYED_RESP)
+	if (msg_type == MSG_TYPE_DELAYED_RESP) {
+		info->desc->ops->clear_channel(cinfo);
 		complete(xfer->async_done);
-	else
+	} else {
 		complete(&xfer->done);
+	}
+}
+
+/**
+ * scmi_rx_callback() - callback for receiving messages
+ *
+ * @cinfo: SCMI channel info
+ * @msg_hdr: Message header
+ *
+ * Processes one received message to appropriate transfer information and
+ * signals completion of the transfer.
+ *
+ * NOTE: This function will be invoked in IRQ context, hence should be
+ * as optimal as possible.
+ */
+void scmi_rx_callback(struct scmi_chan_info *cinfo, u32 msg_hdr)
+{
+	u16 xfer_id = MSG_XTRACT_TOKEN(msg_hdr);
+	u8 msg_type = MSG_XTRACT_TYPE(msg_hdr);
+
+	switch (msg_type) {
+	case MSG_TYPE_NOTIFICATION:
+		scmi_handle_notification(cinfo, msg_hdr);
+		break;
+	case MSG_TYPE_COMMAND:
+	case MSG_TYPE_DELAYED_RESP:
+		scmi_handle_response(cinfo, xfer_id, msg_type);
+		break;
+	default:
+		WARN_ONCE(1, "received unknown msg_type:%d\n", msg_type);
+		break;
+	}
 }
 
 /**
@@ -525,13 +589,13 @@ int scmi_handle_put(const struct scmi_handle *handle)
 	return 0;
 }
 
-static int scmi_xfer_info_init(struct scmi_info *sinfo)
+static int __scmi_xfer_info_init(struct scmi_info *sinfo,
+				 struct scmi_xfers_info *info)
 {
 	int i;
 	struct scmi_xfer *xfer;
 	struct device *dev = sinfo->dev;
 	const struct scmi_desc *desc = sinfo->desc;
-	struct scmi_xfers_info *info = &sinfo->tx_minfo;
 
 	/* Pre-allocated messages, no more than what hdr.seq can support */
 	if (WARN_ON(desc->max_msg >= MSG_TOKEN_MAX)) {
@@ -566,6 +630,16 @@ static int scmi_xfer_info_init(struct scmi_info *sinfo)
 	return 0;
 }
 
+static int scmi_xfer_info_init(struct scmi_info *sinfo)
+{
+	int ret = __scmi_xfer_info_init(sinfo, &sinfo->tx_minfo);
+
+	if (!ret && idr_find(&sinfo->rx_idr, SCMI_PROTOCOL_BASE))
+		ret = __scmi_xfer_info_init(sinfo, &sinfo->rx_minfo);
+
+	return ret;
+}
+
 static int scmi_chan_setup(struct scmi_info *info, struct device *dev,
 			   int prot_id, bool tx)
 {
@@ -699,10 +773,6 @@ static int scmi_probe(struct platform_device *pdev)
 	info->desc = desc;
 	INIT_LIST_HEAD(&info->node);
 
-	ret = scmi_xfer_info_init(info);
-	if (ret)
-		return ret;
-
 	platform_set_drvdata(pdev, info);
 	idr_init(&info->tx_idr);
 	idr_init(&info->rx_idr);
@@ -715,6 +785,10 @@ static int scmi_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	ret = scmi_xfer_info_init(info);
+	if (ret)
+		return ret;
+
 	ret = scmi_base_protocol_init(handle);
 	if (ret) {
 		dev_err(dev, "unable to communicate with SCMI(%d)\n", ret);
@@ -827,6 +901,9 @@ ATTRIBUTE_GROUPS(versions);
 /* Each compatible listed below must have descriptor associated with it */
 static const struct of_device_id scmi_of_match[] = {
 	{ .compatible = "arm,scmi", .data = &scmi_mailbox_desc },
+#ifdef CONFIG_ARM_PSCI_FW
+	{ .compatible = "arm,scmi-smc", .data = &scmi_smc_desc},
+#endif
 	{ /* Sentinel */ },
 };
 

drivers/firmware/arm_scmi/mailbox.c

@@ -158,6 +158,21 @@ static void mailbox_fetch_response(struct scmi_chan_info *cinfo,
 	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)
 {
@@ -173,6 +188,8 @@ static struct scmi_transport_ops scmi_mailbox_ops = {
 	.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,
 };
 

drivers/firmware/arm_scmi/perf.c

@@ -27,6 +27,11 @@ enum scmi_performance_protocol_cmd {
 	PERF_DESCRIBE_FASTCHANNEL = 0xb,
 };
 
+enum scmi_performance_protocol_notify {
+	PERFORMANCE_LIMITS_CHANGED = 0x0,
+	PERFORMANCE_LEVEL_CHANGED = 0x1,
+};
+
 struct scmi_opp {
 	u32 perf;
 	u32 power;

drivers/firmware/arm_scmi/power.c

@@ -12,6 +12,12 @@ enum scmi_power_protocol_cmd {
 	POWER_STATE_SET = 0x4,
 	POWER_STATE_GET = 0x5,
 	POWER_STATE_NOTIFY = 0x6,
+	POWER_STATE_CHANGE_REQUESTED_NOTIFY = 0x7,
+};
+
+enum scmi_power_protocol_notify {
+	POWER_STATE_CHANGED = 0x0,
+	POWER_STATE_CHANGE_REQUESTED = 0x1,
 };
 
 struct scmi_msg_resp_power_attributes {

drivers/firmware/arm_scmi/sensors.c

@@ -14,6 +14,10 @@ enum scmi_sensor_protocol_cmd {
 	SENSOR_READING_GET = 0x6,
 };
 
+enum scmi_sensor_protocol_notify {
+	SENSOR_TRIP_POINT_EVENT = 0x0,
+};
+
 struct scmi_msg_resp_sensor_attributes {
 	__le16 num_sensors;
 	u8 max_requests;

drivers/firmware/arm_scmi/shmem.c

@@ -67,6 +67,21 @@ void shmem_fetch_response(struct scmi_shared_mem __iomem *shmem,
 	memcpy_fromio(xfer->rx.buf, shmem->msg_payload + 4, xfer->rx.len);
 }
 
+void shmem_fetch_notification(struct scmi_shared_mem __iomem *shmem,
+			      size_t max_len, struct scmi_xfer *xfer)
+{
+	/* Skip only the length of header in shmem area i.e 4 bytes */
+	xfer->rx.len = min_t(size_t, max_len, ioread32(&shmem->length) - 4);
+
+	/* Take a copy to the rx buffer.. */
+	memcpy_fromio(xfer->rx.buf, shmem->msg_payload, xfer->rx.len);
+}
+
+void shmem_clear_channel(struct scmi_shared_mem __iomem *shmem)
+{
+	iowrite32(SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE, &shmem->channel_status);
+}
+
 bool shmem_poll_done(struct scmi_shared_mem __iomem *shmem,
 		     struct scmi_xfer *xfer)
 {

drivers/firmware/arm_scmi/smc.c

+// SPDX-License-Identifier: GPL-2.0
+/*
+ * System Control and Management Interface (SCMI) Message SMC/HVC
+ * Transport driver
+ *
+ * Copyright 2020 NXP
+ */
+
+#include <linux/arm-smccc.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/slab.h>
+
+#include "common.h"
+
+/**
+ * struct scmi_smc - Structure representing a SCMI smc transport
+ *
+ * @cinfo: SCMI channel info
+ * @shmem: Transmit/Receive shared memory area
+ * @func_id: smc/hvc call function id
+ */
+
+struct scmi_smc {
+	struct scmi_chan_info *cinfo;
+	struct scmi_shared_mem __iomem *shmem;
+	struct mutex shmem_lock;
+	u32 func_id;
+};
+
+static bool smc_chan_available(struct device *dev, int idx)
+{
+	struct device_node *np = of_parse_phandle(dev->of_node, "shmem", 0);
+	if (!np)
+		return false;
+
+	of_node_put(np);
+	return true;
+}
+
+static int smc_chan_setup(struct scmi_chan_info *cinfo, struct device *dev,
+			  bool tx)
+{
+	struct device *cdev = cinfo->dev;
+	struct scmi_smc *scmi_info;
+	resource_size_t size;
+	struct resource res;
+	struct device_node *np;
+	u32 func_id;
+	int ret;
+
+	if (!tx)
+		return -ENODEV;
+
+	scmi_info = devm_kzalloc(dev, sizeof(*scmi_info), GFP_KERNEL);
+	if (!scmi_info)
+		return -ENOMEM;
+
+	np = of_parse_phandle(cdev->of_node, "shmem", 0);
+	ret = of_address_to_resource(np, 0, &res);
+	of_node_put(np);
+	if (ret) {
+		dev_err(cdev, "failed to get SCMI Tx shared memory\n");
+		return ret;
+	}
+
+	size = resource_size(&res);
+	scmi_info->shmem = devm_ioremap(dev, res.start, size);
+	if (!scmi_info->shmem) {
+		dev_err(dev, "failed to ioremap SCMI Tx shared memory\n");
+		return -EADDRNOTAVAIL;
+	}
+
+	ret = of_property_read_u32(dev->of_node, "arm,smc-id", &func_id);
+	if (ret < 0)
+		return ret;
+
+	scmi_info->func_id = func_id;
+	scmi_info->cinfo = cinfo;
+	mutex_init(&scmi_info->shmem_lock);
+	cinfo->transport_info = scmi_info;
+
+	return 0;
+}
+
+static int smc_chan_free(int id, void *p, void *data)
+{
+	struct scmi_chan_info *cinfo = p;
+	struct scmi_smc *scmi_info = cinfo->transport_info;
+
+	cinfo->transport_info = NULL;
+	scmi_info->cinfo = NULL;
+
+	scmi_free_channel(cinfo, data, id);
+
+	return 0;
+}
+
+static int smc_send_message(struct scmi_chan_info *cinfo,
+			    struct scmi_xfer *xfer)
+{
+	struct scmi_smc *scmi_info = cinfo->transport_info;
+	struct arm_smccc_res res;
+
+	mutex_lock(&scmi_info->shmem_lock);
+
+	shmem_tx_prepare(scmi_info->shmem, xfer);
+
+	arm_smccc_1_1_invoke(scmi_info->func_id, 0, 0, 0, 0, 0, 0, 0, &res);
+	scmi_rx_callback(scmi_info->cinfo, shmem_read_header(scmi_info->shmem));
+
+	mutex_unlock(&scmi_info->shmem_lock);
+
+	/* Only SMCCC_RET_NOT_SUPPORTED is valid error code */
+	if (res.a0)
+		return -EOPNOTSUPP;
+	return 0;
+}
+
+static void smc_fetch_response(struct scmi_chan_info *cinfo,
+			       struct scmi_xfer *xfer)
+{
+	struct scmi_smc *scmi_info = cinfo->transport_info;
+
+	shmem_fetch_response(scmi_info->shmem, xfer);
+}
+
+static bool
+smc_poll_done(struct scmi_chan_info *cinfo, struct scmi_xfer *xfer)
+{
+	struct scmi_smc *scmi_info = cinfo->transport_info;
+
+	return shmem_poll_done(scmi_info->shmem, xfer);
+}
+
+static struct scmi_transport_ops scmi_smc_ops = {
+	.chan_available = smc_chan_available,
+	.chan_setup = smc_chan_setup,
+	.chan_free = smc_chan_free,
+	.send_message = smc_send_message,
+	.fetch_response = smc_fetch_response,
+	.poll_done = smc_poll_done,
+};
+
+const struct scmi_desc scmi_smc_desc = {
+	.ops = &scmi_smc_ops,
+	.max_rx_timeout_ms = 30,
+	.max_msg = 1,
+	.max_msg_size = 128,
+};

include/linux/scmi_protocol.h

@@ -4,6 +4,10 @@
  *
  * Copyright (C) 2018 ARM Ltd.
  */
+
+#ifndef _LINUX_SCMI_PROTOCOL_H
+#define _LINUX_SCMI_PROTOCOL_H
+
 #include <linux/device.h>
 #include <linux/types.h>
 
@@ -319,3 +323,5 @@ static inline void scmi_driver_unregister(struct scmi_driver *driver) {}
 typedef int (*scmi_prot_init_fn_t)(struct scmi_handle *);
 int scmi_protocol_register(int protocol_id, scmi_prot_init_fn_t fn);
 void scmi_protocol_unregister(int protocol_id);
+
+#endif /* _LINUX_SCMI_PROTOCOL_H */

include/linux/scpi_protocol.h

@@ -4,6 +4,10 @@
  *
  * Copyright (C) 2014 ARM Ltd.
  */
+
+#ifndef _LINUX_SCPI_PROTOCOL_H
+#define _LINUX_SCPI_PROTOCOL_H
+
 #include <linux/types.h>
 
 struct scpi_opp {
@@ -71,3 +75,5 @@ struct scpi_ops *get_scpi_ops(void);
 #else
 static inline struct scpi_ops *get_scpi_ops(void) { return NULL; }
 #endif
+
+#endif /* _LINUX_SCPI_PROTOCOL_H */