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[Xen-devel] [RFC PATCH 17/31] xen/arm: Add ARM System Control and Power Interface (SCPI) protocol



From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>

This code is completely borrowed from the Linux. Please see:
http://elixir.free-electrons.com/linux/v4.14-rc6/source/drivers/firmware/arm_scpi.c
http://elixir.free-electrons.com/linux/v4.14-rc6/source/include/linux/scpi_protocol.h

Bindings are here:
http://elixir.free-electrons.com/linux/v4.14-rc6/source/Documentation/devicetree/bindings/arm/arm,scpi.txt

Recent protocol version you can find here:
http://infocenter.arm.com/help/topic/com.arm.doc.dui0922g/scp_message_interface_v1_2_DUI0922G_en.pdf

I port this protocol with having CPUFreq on ARM in mind.

Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Julien Grall <julien.grall@xxxxxxxxxx>
---
 xen/arch/arm/cpufreq/arm_scpi.c      | 1085 ++++++++++++++++++++++++++++++++++
 xen/arch/arm/cpufreq/scpi_protocol.h |   84 +++
 2 files changed, 1169 insertions(+)
 create mode 100644 xen/arch/arm/cpufreq/arm_scpi.c
 create mode 100644 xen/arch/arm/cpufreq/scpi_protocol.h

diff --git a/xen/arch/arm/cpufreq/arm_scpi.c b/xen/arch/arm/cpufreq/arm_scpi.c
new file mode 100644
index 0000000..7da9f1b
--- /dev/null
+++ b/xen/arch/arm/cpufreq/arm_scpi.c
@@ -0,0 +1,1085 @@
+/*
+ * System Control and Power Interface (SCPI) Message Protocol driver
+ *
+ * SCPI Message Protocol is used between the System Control Processor(SCP)
+ * and the Application Processors(AP). The Message Handling Unit(MHU)
+ * provides a mechanism for inter-processor communication between SCP's
+ * Cortex M3 and AP.
+ *
+ * SCP offers control and management of the core/cluster power states,
+ * various power domain DVFS including the core/cluster, certain system
+ * clocks configuration, thermal sensors and many others.
+ *
+ * Copyright (C) 2015 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/bitmap.h>
+#include <linux/device.h>
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/mailbox_client.h>
+#include <linux/module.h>
+#include <linux/of_address.h>
+#include <linux/of_platform.h>
+#include <linux/printk.h>
+#include <linux/pm_opp.h>
+#include <linux/scpi_protocol.h>
+#include <linux/slab.h>
+#include <linux/sort.h>
+#include <linux/spinlock.h>
+
+#define CMD_ID_SHIFT           0
+#define CMD_ID_MASK            0x7f
+#define CMD_TOKEN_ID_SHIFT     8
+#define CMD_TOKEN_ID_MASK      0xff
+#define CMD_DATA_SIZE_SHIFT    16
+#define CMD_DATA_SIZE_MASK     0x1ff
+#define CMD_LEGACY_DATA_SIZE_SHIFT     20
+#define CMD_LEGACY_DATA_SIZE_MASK      0x1ff
+#define PACK_SCPI_CMD(cmd_id, tx_sz)                   \
+       ((((cmd_id) & CMD_ID_MASK) << CMD_ID_SHIFT) |   \
+       (((tx_sz) & CMD_DATA_SIZE_MASK) << CMD_DATA_SIZE_SHIFT))
+#define ADD_SCPI_TOKEN(cmd, token)                     \
+       ((cmd) |= (((token) & CMD_TOKEN_ID_MASK) << CMD_TOKEN_ID_SHIFT))
+#define PACK_LEGACY_SCPI_CMD(cmd_id, tx_sz)                            \
+       ((((cmd_id) & CMD_ID_MASK) << CMD_ID_SHIFT) |                          \
+       (((tx_sz) & CMD_LEGACY_DATA_SIZE_MASK) << CMD_LEGACY_DATA_SIZE_SHIFT))
+
+#define CMD_SIZE(cmd)  (((cmd) >> CMD_DATA_SIZE_SHIFT) & CMD_DATA_SIZE_MASK)
+#define CMD_LEGACY_SIZE(cmd)   (((cmd) >> CMD_LEGACY_DATA_SIZE_SHIFT) & \
+                                       CMD_LEGACY_DATA_SIZE_MASK)
+#define CMD_UNIQ_MASK  (CMD_TOKEN_ID_MASK << CMD_TOKEN_ID_SHIFT | CMD_ID_MASK)
+#define CMD_XTRACT_UNIQ(cmd)   ((cmd) & CMD_UNIQ_MASK)
+
+#define SCPI_SLOT              0
+
+#define MAX_DVFS_DOMAINS       8
+#define MAX_DVFS_OPPS          16
+#define DVFS_LATENCY(hdr)      (le32_to_cpu(hdr) >> 16)
+#define DVFS_OPP_COUNT(hdr)    ((le32_to_cpu(hdr) >> 8) & 0xff)
+
+#define PROTOCOL_REV_MINOR_BITS        16
+#define PROTOCOL_REV_MINOR_MASK        ((1U << PROTOCOL_REV_MINOR_BITS) - 1)
+#define PROTOCOL_REV_MAJOR(x)  ((x) >> PROTOCOL_REV_MINOR_BITS)
+#define PROTOCOL_REV_MINOR(x)  ((x) & PROTOCOL_REV_MINOR_MASK)
+
+#define FW_REV_MAJOR_BITS      24
+#define FW_REV_MINOR_BITS      16
+#define FW_REV_PATCH_MASK      ((1U << FW_REV_MINOR_BITS) - 1)
+#define FW_REV_MINOR_MASK      ((1U << FW_REV_MAJOR_BITS) - 1)
+#define FW_REV_MAJOR(x)                ((x) >> FW_REV_MAJOR_BITS)
+#define FW_REV_MINOR(x)                (((x) & FW_REV_MINOR_MASK) >> 
FW_REV_MINOR_BITS)
+#define FW_REV_PATCH(x)                ((x) & FW_REV_PATCH_MASK)
+
+#define MAX_RX_TIMEOUT         (msecs_to_jiffies(30))
+
+enum scpi_error_codes {
+       SCPI_SUCCESS = 0, /* Success */
+       SCPI_ERR_PARAM = 1, /* Invalid parameter(s) */
+       SCPI_ERR_ALIGN = 2, /* Invalid alignment */
+       SCPI_ERR_SIZE = 3, /* Invalid size */
+       SCPI_ERR_HANDLER = 4, /* Invalid handler/callback */
+       SCPI_ERR_ACCESS = 5, /* Invalid access/permission denied */
+       SCPI_ERR_RANGE = 6, /* Value out of range */
+       SCPI_ERR_TIMEOUT = 7, /* Timeout has occurred */
+       SCPI_ERR_NOMEM = 8, /* Invalid memory area or pointer */
+       SCPI_ERR_PWRSTATE = 9, /* Invalid power state */
+       SCPI_ERR_SUPPORT = 10, /* Not supported or disabled */
+       SCPI_ERR_DEVICE = 11, /* Device error */
+       SCPI_ERR_BUSY = 12, /* Device busy */
+       SCPI_ERR_MAX
+};
+
+/* SCPI Standard commands */
+enum scpi_std_cmd {
+       SCPI_CMD_INVALID                = 0x00,
+       SCPI_CMD_SCPI_READY             = 0x01,
+       SCPI_CMD_SCPI_CAPABILITIES      = 0x02,
+       SCPI_CMD_SET_CSS_PWR_STATE      = 0x03,
+       SCPI_CMD_GET_CSS_PWR_STATE      = 0x04,
+       SCPI_CMD_SET_SYS_PWR_STATE      = 0x05,
+       SCPI_CMD_SET_CPU_TIMER          = 0x06,
+       SCPI_CMD_CANCEL_CPU_TIMER       = 0x07,
+       SCPI_CMD_DVFS_CAPABILITIES      = 0x08,
+       SCPI_CMD_GET_DVFS_INFO          = 0x09,
+       SCPI_CMD_SET_DVFS               = 0x0a,
+       SCPI_CMD_GET_DVFS               = 0x0b,
+       SCPI_CMD_GET_DVFS_STAT          = 0x0c,
+       SCPI_CMD_CLOCK_CAPABILITIES     = 0x0d,
+       SCPI_CMD_GET_CLOCK_INFO         = 0x0e,
+       SCPI_CMD_SET_CLOCK_VALUE        = 0x0f,
+       SCPI_CMD_GET_CLOCK_VALUE        = 0x10,
+       SCPI_CMD_PSU_CAPABILITIES       = 0x11,
+       SCPI_CMD_GET_PSU_INFO           = 0x12,
+       SCPI_CMD_SET_PSU                = 0x13,
+       SCPI_CMD_GET_PSU                = 0x14,
+       SCPI_CMD_SENSOR_CAPABILITIES    = 0x15,
+       SCPI_CMD_SENSOR_INFO            = 0x16,
+       SCPI_CMD_SENSOR_VALUE           = 0x17,
+       SCPI_CMD_SENSOR_CFG_PERIODIC    = 0x18,
+       SCPI_CMD_SENSOR_CFG_BOUNDS      = 0x19,
+       SCPI_CMD_SENSOR_ASYNC_VALUE     = 0x1a,
+       SCPI_CMD_SET_DEVICE_PWR_STATE   = 0x1b,
+       SCPI_CMD_GET_DEVICE_PWR_STATE   = 0x1c,
+       SCPI_CMD_COUNT
+};
+
+/* SCPI Legacy Commands */
+enum legacy_scpi_std_cmd {
+       LEGACY_SCPI_CMD_INVALID                 = 0x00,
+       LEGACY_SCPI_CMD_SCPI_READY              = 0x01,
+       LEGACY_SCPI_CMD_SCPI_CAPABILITIES       = 0x02,
+       LEGACY_SCPI_CMD_EVENT                   = 0x03,
+       LEGACY_SCPI_CMD_SET_CSS_PWR_STATE       = 0x04,
+       LEGACY_SCPI_CMD_GET_CSS_PWR_STATE       = 0x05,
+       LEGACY_SCPI_CMD_CFG_PWR_STATE_STAT      = 0x06,
+       LEGACY_SCPI_CMD_GET_PWR_STATE_STAT      = 0x07,
+       LEGACY_SCPI_CMD_SYS_PWR_STATE           = 0x08,
+       LEGACY_SCPI_CMD_L2_READY                = 0x09,
+       LEGACY_SCPI_CMD_SET_AP_TIMER            = 0x0a,
+       LEGACY_SCPI_CMD_CANCEL_AP_TIME          = 0x0b,
+       LEGACY_SCPI_CMD_DVFS_CAPABILITIES       = 0x0c,
+       LEGACY_SCPI_CMD_GET_DVFS_INFO           = 0x0d,
+       LEGACY_SCPI_CMD_SET_DVFS                = 0x0e,
+       LEGACY_SCPI_CMD_GET_DVFS                = 0x0f,
+       LEGACY_SCPI_CMD_GET_DVFS_STAT           = 0x10,
+       LEGACY_SCPI_CMD_SET_RTC                 = 0x11,
+       LEGACY_SCPI_CMD_GET_RTC                 = 0x12,
+       LEGACY_SCPI_CMD_CLOCK_CAPABILITIES      = 0x13,
+       LEGACY_SCPI_CMD_SET_CLOCK_INDEX         = 0x14,
+       LEGACY_SCPI_CMD_SET_CLOCK_VALUE         = 0x15,
+       LEGACY_SCPI_CMD_GET_CLOCK_VALUE         = 0x16,
+       LEGACY_SCPI_CMD_PSU_CAPABILITIES        = 0x17,
+       LEGACY_SCPI_CMD_SET_PSU                 = 0x18,
+       LEGACY_SCPI_CMD_GET_PSU                 = 0x19,
+       LEGACY_SCPI_CMD_SENSOR_CAPABILITIES     = 0x1a,
+       LEGACY_SCPI_CMD_SENSOR_INFO             = 0x1b,
+       LEGACY_SCPI_CMD_SENSOR_VALUE            = 0x1c,
+       LEGACY_SCPI_CMD_SENSOR_CFG_PERIODIC     = 0x1d,
+       LEGACY_SCPI_CMD_SENSOR_CFG_BOUNDS       = 0x1e,
+       LEGACY_SCPI_CMD_SENSOR_ASYNC_VALUE      = 0x1f,
+       LEGACY_SCPI_CMD_COUNT
+};
+
+/* List all commands that are required to go through the high priority link */
+static int legacy_hpriority_cmds[] = {
+       LEGACY_SCPI_CMD_GET_CSS_PWR_STATE,
+       LEGACY_SCPI_CMD_CFG_PWR_STATE_STAT,
+       LEGACY_SCPI_CMD_GET_PWR_STATE_STAT,
+       LEGACY_SCPI_CMD_SET_DVFS,
+       LEGACY_SCPI_CMD_GET_DVFS,
+       LEGACY_SCPI_CMD_SET_RTC,
+       LEGACY_SCPI_CMD_GET_RTC,
+       LEGACY_SCPI_CMD_SET_CLOCK_INDEX,
+       LEGACY_SCPI_CMD_SET_CLOCK_VALUE,
+       LEGACY_SCPI_CMD_GET_CLOCK_VALUE,
+       LEGACY_SCPI_CMD_SET_PSU,
+       LEGACY_SCPI_CMD_GET_PSU,
+       LEGACY_SCPI_CMD_SENSOR_CFG_PERIODIC,
+       LEGACY_SCPI_CMD_SENSOR_CFG_BOUNDS,
+};
+
+/* List all commands used by this driver, used as indexes */
+enum scpi_drv_cmds {
+       CMD_SCPI_CAPABILITIES = 0,
+       CMD_GET_CLOCK_INFO,
+       CMD_GET_CLOCK_VALUE,
+       CMD_SET_CLOCK_VALUE,
+       CMD_GET_DVFS,
+       CMD_SET_DVFS,
+       CMD_GET_DVFS_INFO,
+       CMD_SENSOR_CAPABILITIES,
+       CMD_SENSOR_INFO,
+       CMD_SENSOR_VALUE,
+       CMD_SET_DEVICE_PWR_STATE,
+       CMD_GET_DEVICE_PWR_STATE,
+       CMD_MAX_COUNT,
+};
+
+static int scpi_std_commands[CMD_MAX_COUNT] = {
+       SCPI_CMD_SCPI_CAPABILITIES,
+       SCPI_CMD_GET_CLOCK_INFO,
+       SCPI_CMD_GET_CLOCK_VALUE,
+       SCPI_CMD_SET_CLOCK_VALUE,
+       SCPI_CMD_GET_DVFS,
+       SCPI_CMD_SET_DVFS,
+       SCPI_CMD_GET_DVFS_INFO,
+       SCPI_CMD_SENSOR_CAPABILITIES,
+       SCPI_CMD_SENSOR_INFO,
+       SCPI_CMD_SENSOR_VALUE,
+       SCPI_CMD_SET_DEVICE_PWR_STATE,
+       SCPI_CMD_GET_DEVICE_PWR_STATE,
+};
+
+static int scpi_legacy_commands[CMD_MAX_COUNT] = {
+       LEGACY_SCPI_CMD_SCPI_CAPABILITIES,
+       -1, /* GET_CLOCK_INFO */
+       LEGACY_SCPI_CMD_GET_CLOCK_VALUE,
+       LEGACY_SCPI_CMD_SET_CLOCK_VALUE,
+       LEGACY_SCPI_CMD_GET_DVFS,
+       LEGACY_SCPI_CMD_SET_DVFS,
+       LEGACY_SCPI_CMD_GET_DVFS_INFO,
+       LEGACY_SCPI_CMD_SENSOR_CAPABILITIES,
+       LEGACY_SCPI_CMD_SENSOR_INFO,
+       LEGACY_SCPI_CMD_SENSOR_VALUE,
+       -1, /* SET_DEVICE_PWR_STATE */
+       -1, /* GET_DEVICE_PWR_STATE */
+};
+
+struct scpi_xfer {
+       u32 slot; /* has to be first element */
+       u32 cmd;
+       u32 status;
+       const void *tx_buf;
+       void *rx_buf;
+       unsigned int tx_len;
+       unsigned int rx_len;
+       struct list_head node;
+       struct completion done;
+};
+
+struct scpi_chan {
+       struct mbox_client cl;
+       struct mbox_chan *chan;
+       void __iomem *tx_payload;
+       void __iomem *rx_payload;
+       struct list_head rx_pending;
+       struct list_head xfers_list;
+       struct scpi_xfer *xfers;
+       spinlock_t rx_lock; /* locking for the rx pending list */
+       struct mutex xfers_lock;
+       u8 token;
+};
+
+struct scpi_drvinfo {
+       u32 protocol_version;
+       u32 firmware_version;
+       bool is_legacy;
+       int num_chans;
+       int *commands;
+       DECLARE_BITMAP(cmd_priority, LEGACY_SCPI_CMD_COUNT);
+       atomic_t next_chan;
+       struct scpi_ops *scpi_ops;
+       struct scpi_chan *channels;
+       struct scpi_dvfs_info *dvfs[MAX_DVFS_DOMAINS];
+};
+
+/*
+ * The SCP firmware only executes in little-endian mode, so any buffers
+ * shared through SCPI should have their contents converted to little-endian
+ */
+struct scpi_shared_mem {
+       __le32 command;
+       __le32 status;
+       u8 payload[0];
+} __packed;
+
+struct legacy_scpi_shared_mem {
+       __le32 status;
+       u8 payload[0];
+} __packed;
+
+struct scp_capabilities {
+       __le32 protocol_version;
+       __le32 event_version;
+       __le32 platform_version;
+       __le32 commands[4];
+} __packed;
+
+struct clk_get_info {
+       __le16 id;
+       __le16 flags;
+       __le32 min_rate;
+       __le32 max_rate;
+       u8 name[20];
+} __packed;
+
+struct clk_get_value {
+       __le32 rate;
+} __packed;
+
+struct clk_set_value {
+       __le16 id;
+       __le16 reserved;
+       __le32 rate;
+} __packed;
+
+struct legacy_clk_set_value {
+       __le32 rate;
+       __le16 id;
+       __le16 reserved;
+} __packed;
+
+struct dvfs_info {
+       __le32 header;
+       struct {
+               __le32 freq;
+               __le32 m_volt;
+       } opps[MAX_DVFS_OPPS];
+} __packed;
+
+struct dvfs_set {
+       u8 domain;
+       u8 index;
+} __packed;
+
+struct sensor_capabilities {
+       __le16 sensors;
+} __packed;
+
+struct _scpi_sensor_info {
+       __le16 sensor_id;
+       u8 class;
+       u8 trigger_type;
+       char name[20];
+};
+
+struct sensor_value {
+       __le32 lo_val;
+       __le32 hi_val;
+} __packed;
+
+struct dev_pstate_set {
+       __le16 dev_id;
+       u8 pstate;
+} __packed;
+
+static struct scpi_drvinfo *scpi_info;
+
+static int scpi_linux_errmap[SCPI_ERR_MAX] = {
+       /* better than switch case as long as return value is continuous */
+       0, /* SCPI_SUCCESS */
+       -EINVAL, /* SCPI_ERR_PARAM */
+       -ENOEXEC, /* SCPI_ERR_ALIGN */
+       -EMSGSIZE, /* SCPI_ERR_SIZE */
+       -EINVAL, /* SCPI_ERR_HANDLER */
+       -EACCES, /* SCPI_ERR_ACCESS */
+       -ERANGE, /* SCPI_ERR_RANGE */
+       -ETIMEDOUT, /* SCPI_ERR_TIMEOUT */
+       -ENOMEM, /* SCPI_ERR_NOMEM */
+       -EINVAL, /* SCPI_ERR_PWRSTATE */
+       -EOPNOTSUPP, /* SCPI_ERR_SUPPORT */
+       -EIO, /* SCPI_ERR_DEVICE */
+       -EBUSY, /* SCPI_ERR_BUSY */
+};
+
+static inline int scpi_to_linux_errno(int errno)
+{
+       if (errno >= SCPI_SUCCESS && errno < SCPI_ERR_MAX)
+               return scpi_linux_errmap[errno];
+       return -EIO;
+}
+
+static void scpi_process_cmd(struct scpi_chan *ch, u32 cmd)
+{
+       unsigned long flags;
+       struct scpi_xfer *t, *match = NULL;
+
+       spin_lock_irqsave(&ch->rx_lock, flags);
+       if (list_empty(&ch->rx_pending)) {
+               spin_unlock_irqrestore(&ch->rx_lock, flags);
+               return;
+       }
+
+       /* Command type is not replied by the SCP Firmware in legacy Mode
+        * We should consider that command is the head of pending RX commands
+        * if the list is not empty. In TX only mode, the list would be empty.
+        */
+       if (scpi_info->is_legacy) {
+               match = list_first_entry(&ch->rx_pending, struct scpi_xfer,
+                                        node);
+               list_del(&match->node);
+       } else {
+               list_for_each_entry(t, &ch->rx_pending, node)
+                       if (CMD_XTRACT_UNIQ(t->cmd) == CMD_XTRACT_UNIQ(cmd)) {
+                               list_del(&t->node);
+                               match = t;
+                               break;
+                       }
+       }
+       /* check if wait_for_completion is in progress or timed-out */
+       if (match && !completion_done(&match->done)) {
+               unsigned int len;
+
+               if (scpi_info->is_legacy) {
+                       struct legacy_scpi_shared_mem *mem = ch->rx_payload;
+
+                       /* RX Length is not replied by the legacy Firmware */
+                       len = match->rx_len;
+
+                       match->status = le32_to_cpu(mem->status);
+                       memcpy_fromio(match->rx_buf, mem->payload, len);
+               } else {
+                       struct scpi_shared_mem *mem = ch->rx_payload;
+
+                       len = min(match->rx_len, CMD_SIZE(cmd));
+
+                       match->status = le32_to_cpu(mem->status);
+                       memcpy_fromio(match->rx_buf, mem->payload, len);
+               }
+
+               if (match->rx_len > len)
+                       memset(match->rx_buf + len, 0, match->rx_len - len);
+               complete(&match->done);
+       }
+       spin_unlock_irqrestore(&ch->rx_lock, flags);
+}
+
+static void scpi_handle_remote_msg(struct mbox_client *c, void *msg)
+{
+       struct scpi_chan *ch = container_of(c, struct scpi_chan, cl);
+       struct scpi_shared_mem *mem = ch->rx_payload;
+       u32 cmd = 0;
+
+       if (!scpi_info->is_legacy)
+               cmd = le32_to_cpu(mem->command);
+
+       scpi_process_cmd(ch, cmd);
+}
+
+static void scpi_tx_prepare(struct mbox_client *c, void *msg)
+{
+       unsigned long flags;
+       struct scpi_xfer *t = msg;
+       struct scpi_chan *ch = container_of(c, struct scpi_chan, cl);
+       struct scpi_shared_mem *mem = (struct scpi_shared_mem *)ch->tx_payload;
+
+       if (t->tx_buf) {
+               if (scpi_info->is_legacy)
+                       memcpy_toio(ch->tx_payload, t->tx_buf, t->tx_len);
+               else
+                       memcpy_toio(mem->payload, t->tx_buf, t->tx_len);
+       }
+
+       if (t->rx_buf) {
+               if (!(++ch->token))
+                       ++ch->token;
+               ADD_SCPI_TOKEN(t->cmd, ch->token);
+               spin_lock_irqsave(&ch->rx_lock, flags);
+               list_add_tail(&t->node, &ch->rx_pending);
+               spin_unlock_irqrestore(&ch->rx_lock, flags);
+       }
+
+       if (!scpi_info->is_legacy)
+               mem->command = cpu_to_le32(t->cmd);
+}
+
+static struct scpi_xfer *get_scpi_xfer(struct scpi_chan *ch)
+{
+       struct scpi_xfer *t;
+
+       mutex_lock(&ch->xfers_lock);
+       if (list_empty(&ch->xfers_list)) {
+               mutex_unlock(&ch->xfers_lock);
+               return NULL;
+       }
+       t = list_first_entry(&ch->xfers_list, struct scpi_xfer, node);
+       list_del(&t->node);
+       mutex_unlock(&ch->xfers_lock);
+       return t;
+}
+
+static void put_scpi_xfer(struct scpi_xfer *t, struct scpi_chan *ch)
+{
+       mutex_lock(&ch->xfers_lock);
+       list_add_tail(&t->node, &ch->xfers_list);
+       mutex_unlock(&ch->xfers_lock);
+}
+
+static int scpi_send_message(u8 idx, void *tx_buf, unsigned int tx_len,
+                            void *rx_buf, unsigned int rx_len)
+{
+       int ret;
+       u8 chan;
+       u8 cmd;
+       struct scpi_xfer *msg;
+       struct scpi_chan *scpi_chan;
+
+       if (scpi_info->commands[idx] < 0)
+               return -EOPNOTSUPP;
+
+       cmd = scpi_info->commands[idx];
+
+       if (scpi_info->is_legacy)
+               chan = test_bit(cmd, scpi_info->cmd_priority) ? 1 : 0;
+       else
+               chan = atomic_inc_return(&scpi_info->next_chan) %
+                       scpi_info->num_chans;
+       scpi_chan = scpi_info->channels + chan;
+
+       msg = get_scpi_xfer(scpi_chan);
+       if (!msg)
+               return -ENOMEM;
+
+       if (scpi_info->is_legacy) {
+               msg->cmd = PACK_LEGACY_SCPI_CMD(cmd, tx_len);
+               msg->slot = msg->cmd;
+       } else {
+               msg->slot = BIT(SCPI_SLOT);
+               msg->cmd = PACK_SCPI_CMD(cmd, tx_len);
+       }
+       msg->tx_buf = tx_buf;
+       msg->tx_len = tx_len;
+       msg->rx_buf = rx_buf;
+       msg->rx_len = rx_len;
+       reinit_completion(&msg->done);
+
+       ret = mbox_send_message(scpi_chan->chan, msg);
+       if (ret < 0 || !rx_buf)
+               goto out;
+
+       if (!wait_for_completion_timeout(&msg->done, MAX_RX_TIMEOUT))
+               ret = -ETIMEDOUT;
+       else
+               /* first status word */
+               ret = msg->status;
+out:
+       if (ret < 0 && rx_buf) /* remove entry from the list if timed-out */
+               scpi_process_cmd(scpi_chan, msg->cmd);
+
+       put_scpi_xfer(msg, scpi_chan);
+       /* SCPI error codes > 0, translate them to Linux scale*/
+       return ret > 0 ? scpi_to_linux_errno(ret) : ret;
+}
+
+static u32 scpi_get_version(void)
+{
+       return scpi_info->protocol_version;
+}
+
+static int
+scpi_clk_get_range(u16 clk_id, unsigned long *min, unsigned long *max)
+{
+       int ret;
+       struct clk_get_info clk;
+       __le16 le_clk_id = cpu_to_le16(clk_id);
+
+       ret = scpi_send_message(CMD_GET_CLOCK_INFO, &le_clk_id,
+                               sizeof(le_clk_id), &clk, sizeof(clk));
+       if (!ret) {
+               *min = le32_to_cpu(clk.min_rate);
+               *max = le32_to_cpu(clk.max_rate);
+       }
+       return ret;
+}
+
+static unsigned long scpi_clk_get_val(u16 clk_id)
+{
+       int ret;
+       struct clk_get_value clk;
+       __le16 le_clk_id = cpu_to_le16(clk_id);
+
+       ret = scpi_send_message(CMD_GET_CLOCK_VALUE, &le_clk_id,
+                               sizeof(le_clk_id), &clk, sizeof(clk));
+
+       return ret ? ret : le32_to_cpu(clk.rate);
+}
+
+static int scpi_clk_set_val(u16 clk_id, unsigned long rate)
+{
+       int stat;
+       struct clk_set_value clk = {
+               .id = cpu_to_le16(clk_id),
+               .rate = cpu_to_le32(rate)
+       };
+
+       return scpi_send_message(CMD_SET_CLOCK_VALUE, &clk, sizeof(clk),
+                                &stat, sizeof(stat));
+}
+
+static int legacy_scpi_clk_set_val(u16 clk_id, unsigned long rate)
+{
+       int stat;
+       struct legacy_clk_set_value clk = {
+               .id = cpu_to_le16(clk_id),
+               .rate = cpu_to_le32(rate)
+       };
+
+       return scpi_send_message(CMD_SET_CLOCK_VALUE, &clk, sizeof(clk),
+                                &stat, sizeof(stat));
+}
+
+static int scpi_dvfs_get_idx(u8 domain)
+{
+       int ret;
+       u8 dvfs_idx;
+
+       ret = scpi_send_message(CMD_GET_DVFS, &domain, sizeof(domain),
+                               &dvfs_idx, sizeof(dvfs_idx));
+
+       return ret ? ret : dvfs_idx;
+}
+
+static int scpi_dvfs_set_idx(u8 domain, u8 index)
+{
+       int stat;
+       struct dvfs_set dvfs = {domain, index};
+
+       return scpi_send_message(CMD_SET_DVFS, &dvfs, sizeof(dvfs),
+                                &stat, sizeof(stat));
+}
+
+static int opp_cmp_func(const void *opp1, const void *opp2)
+{
+       const struct scpi_opp *t1 = opp1, *t2 = opp2;
+
+       return t1->freq - t2->freq;
+}
+
+static struct scpi_dvfs_info *scpi_dvfs_get_info(u8 domain)
+{
+       struct scpi_dvfs_info *info;
+       struct scpi_opp *opp;
+       struct dvfs_info buf;
+       int ret, i;
+
+       if (domain >= MAX_DVFS_DOMAINS)
+               return ERR_PTR(-EINVAL);
+
+       if (scpi_info->dvfs[domain])    /* data already populated */
+               return scpi_info->dvfs[domain];
+
+       ret = scpi_send_message(CMD_GET_DVFS_INFO, &domain, sizeof(domain),
+                               &buf, sizeof(buf));
+       if (ret)
+               return ERR_PTR(ret);
+
+       info = kmalloc(sizeof(*info), GFP_KERNEL);
+       if (!info)
+               return ERR_PTR(-ENOMEM);
+
+       info->count = DVFS_OPP_COUNT(buf.header);
+       info->latency = DVFS_LATENCY(buf.header) * 1000; /* uS to nS */
+
+       info->opps = kcalloc(info->count, sizeof(*opp), GFP_KERNEL);
+       if (!info->opps) {
+               kfree(info);
+               return ERR_PTR(-ENOMEM);
+       }
+
+       for (i = 0, opp = info->opps; i < info->count; i++, opp++) {
+               opp->freq = le32_to_cpu(buf.opps[i].freq);
+               opp->m_volt = le32_to_cpu(buf.opps[i].m_volt);
+       }
+
+       sort(info->opps, info->count, sizeof(*opp), opp_cmp_func, NULL);
+
+       scpi_info->dvfs[domain] = info;
+       return info;
+}
+
+static int scpi_dev_domain_id(struct device *dev)
+{
+       struct of_phandle_args clkspec;
+
+       if (of_parse_phandle_with_args(dev->of_node, "clocks", "#clock-cells",
+                                      0, &clkspec))
+               return -EINVAL;
+
+       return clkspec.args[0];
+}
+
+static struct scpi_dvfs_info *scpi_dvfs_info(struct device *dev)
+{
+       int domain = scpi_dev_domain_id(dev);
+
+       if (domain < 0)
+               return ERR_PTR(domain);
+
+       return scpi_dvfs_get_info(domain);
+}
+
+static int scpi_dvfs_get_transition_latency(struct device *dev)
+{
+       struct scpi_dvfs_info *info = scpi_dvfs_info(dev);
+
+       if (IS_ERR(info))
+               return PTR_ERR(info);
+
+       if (!info->latency)
+               return 0;
+
+       return info->latency;
+}
+
+static int scpi_dvfs_add_opps_to_device(struct device *dev)
+{
+       int idx, ret;
+       struct scpi_opp *opp;
+       struct scpi_dvfs_info *info = scpi_dvfs_info(dev);
+
+       if (IS_ERR(info))
+               return PTR_ERR(info);
+
+       if (!info->opps)
+               return -EIO;
+
+       for (opp = info->opps, idx = 0; idx < info->count; idx++, opp++) {
+               ret = dev_pm_opp_add(dev, opp->freq, opp->m_volt * 1000);
+               if (ret) {
+                       dev_warn(dev, "failed to add opp %uHz %umV\n",
+                                opp->freq, opp->m_volt);
+                       while (idx-- > 0)
+                               dev_pm_opp_remove(dev, (--opp)->freq);
+                       return ret;
+               }
+       }
+       return 0;
+}
+
+static int scpi_sensor_get_capability(u16 *sensors)
+{
+       struct sensor_capabilities cap_buf;
+       int ret;
+
+       ret = scpi_send_message(CMD_SENSOR_CAPABILITIES, NULL, 0, &cap_buf,
+                               sizeof(cap_buf));
+       if (!ret)
+               *sensors = le16_to_cpu(cap_buf.sensors);
+
+       return ret;
+}
+
+static int scpi_sensor_get_info(u16 sensor_id, struct scpi_sensor_info *info)
+{
+       __le16 id = cpu_to_le16(sensor_id);
+       struct _scpi_sensor_info _info;
+       int ret;
+
+       ret = scpi_send_message(CMD_SENSOR_INFO, &id, sizeof(id),
+                               &_info, sizeof(_info));
+       if (!ret) {
+               memcpy(info, &_info, sizeof(*info));
+               info->sensor_id = le16_to_cpu(_info.sensor_id);
+       }
+
+       return ret;
+}
+
+static int scpi_sensor_get_value(u16 sensor, u64 *val)
+{
+       __le16 id = cpu_to_le16(sensor);
+       struct sensor_value buf;
+       int ret;
+
+       ret = scpi_send_message(CMD_SENSOR_VALUE, &id, sizeof(id),
+                               &buf, sizeof(buf));
+       if (ret)
+               return ret;
+
+       if (scpi_info->is_legacy)
+               /* only 32-bits supported, hi_val can be junk */
+               *val = le32_to_cpu(buf.lo_val);
+       else
+               *val = (u64)le32_to_cpu(buf.hi_val) << 32 |
+                       le32_to_cpu(buf.lo_val);
+
+       return 0;
+}
+
+static int scpi_device_get_power_state(u16 dev_id)
+{
+       int ret;
+       u8 pstate;
+       __le16 id = cpu_to_le16(dev_id);
+
+       ret = scpi_send_message(CMD_GET_DEVICE_PWR_STATE, &id,
+                               sizeof(id), &pstate, sizeof(pstate));
+       return ret ? ret : pstate;
+}
+
+static int scpi_device_set_power_state(u16 dev_id, u8 pstate)
+{
+       int stat;
+       struct dev_pstate_set dev_set = {
+               .dev_id = cpu_to_le16(dev_id),
+               .pstate = pstate,
+       };
+
+       return scpi_send_message(CMD_SET_DEVICE_PWR_STATE, &dev_set,
+                                sizeof(dev_set), &stat, sizeof(stat));
+}
+
+static struct scpi_ops scpi_ops = {
+       .get_version = scpi_get_version,
+       .clk_get_range = scpi_clk_get_range,
+       .clk_get_val = scpi_clk_get_val,
+       .clk_set_val = scpi_clk_set_val,
+       .dvfs_get_idx = scpi_dvfs_get_idx,
+       .dvfs_set_idx = scpi_dvfs_set_idx,
+       .dvfs_get_info = scpi_dvfs_get_info,
+       .device_domain_id = scpi_dev_domain_id,
+       .get_transition_latency = scpi_dvfs_get_transition_latency,
+       .add_opps_to_device = scpi_dvfs_add_opps_to_device,
+       .sensor_get_capability = scpi_sensor_get_capability,
+       .sensor_get_info = scpi_sensor_get_info,
+       .sensor_get_value = scpi_sensor_get_value,
+       .device_get_power_state = scpi_device_get_power_state,
+       .device_set_power_state = scpi_device_set_power_state,
+};
+
+struct scpi_ops *get_scpi_ops(void)
+{
+       return scpi_info ? scpi_info->scpi_ops : NULL;
+}
+EXPORT_SYMBOL_GPL(get_scpi_ops);
+
+static int scpi_init_versions(struct scpi_drvinfo *info)
+{
+       int ret;
+       struct scp_capabilities caps;
+
+       ret = scpi_send_message(CMD_SCPI_CAPABILITIES, NULL, 0,
+                               &caps, sizeof(caps));
+       if (!ret) {
+               info->protocol_version = le32_to_cpu(caps.protocol_version);
+               info->firmware_version = le32_to_cpu(caps.platform_version);
+       }
+       /* Ignore error if not implemented */
+       if (scpi_info->is_legacy && ret == -EOPNOTSUPP)
+               return 0;
+
+       return ret;
+}
+
+static ssize_t protocol_version_show(struct device *dev,
+                                    struct device_attribute *attr, char *buf)
+{
+       struct scpi_drvinfo *scpi_info = dev_get_drvdata(dev);
+
+       return sprintf(buf, "%d.%d\n",
+                      PROTOCOL_REV_MAJOR(scpi_info->protocol_version),
+                      PROTOCOL_REV_MINOR(scpi_info->protocol_version));
+}
+static DEVICE_ATTR_RO(protocol_version);
+
+static ssize_t firmware_version_show(struct device *dev,
+                                    struct device_attribute *attr, char *buf)
+{
+       struct scpi_drvinfo *scpi_info = dev_get_drvdata(dev);
+
+       return sprintf(buf, "%d.%d.%d\n",
+                      FW_REV_MAJOR(scpi_info->firmware_version),
+                      FW_REV_MINOR(scpi_info->firmware_version),
+                      FW_REV_PATCH(scpi_info->firmware_version));
+}
+static DEVICE_ATTR_RO(firmware_version);
+
+static struct attribute *versions_attrs[] = {
+       &dev_attr_firmware_version.attr,
+       &dev_attr_protocol_version.attr,
+       NULL,
+};
+ATTRIBUTE_GROUPS(versions);
+
+static void
+scpi_free_channels(struct device *dev, struct scpi_chan *pchan, int count)
+{
+       int i;
+
+       for (i = 0; i < count && pchan->chan; i++, pchan++) {
+               mbox_free_channel(pchan->chan);
+               devm_kfree(dev, pchan->xfers);
+               devm_iounmap(dev, pchan->rx_payload);
+       }
+}
+
+static int scpi_remove(struct platform_device *pdev)
+{
+       int i;
+       struct device *dev = &pdev->dev;
+       struct scpi_drvinfo *info = platform_get_drvdata(pdev);
+
+       scpi_info = NULL; /* stop exporting SCPI ops through get_scpi_ops */
+
+       of_platform_depopulate(dev);
+       sysfs_remove_groups(&dev->kobj, versions_groups);
+       scpi_free_channels(dev, info->channels, info->num_chans);
+       platform_set_drvdata(pdev, NULL);
+
+       for (i = 0; i < MAX_DVFS_DOMAINS && info->dvfs[i]; i++) {
+               kfree(info->dvfs[i]->opps);
+               kfree(info->dvfs[i]);
+       }
+       devm_kfree(dev, info->channels);
+       devm_kfree(dev, info);
+
+       return 0;
+}
+
+#define MAX_SCPI_XFERS         10
+static int scpi_alloc_xfer_list(struct device *dev, struct scpi_chan *ch)
+{
+       int i;
+       struct scpi_xfer *xfers;
+
+       xfers = devm_kzalloc(dev, MAX_SCPI_XFERS * sizeof(*xfers), GFP_KERNEL);
+       if (!xfers)
+               return -ENOMEM;
+
+       ch->xfers = xfers;
+       for (i = 0; i < MAX_SCPI_XFERS; i++, xfers++) {
+               init_completion(&xfers->done);
+               list_add_tail(&xfers->node, &ch->xfers_list);
+       }
+
+       return 0;
+}
+
+static const struct of_device_id legacy_scpi_of_match[] = {
+       {.compatible = "arm,scpi-pre-1.0"},
+       {},
+};
+
+static int scpi_probe(struct platform_device *pdev)
+{
+       int count, idx, ret;
+       struct resource res;
+       struct scpi_chan *scpi_chan;
+       struct device *dev = &pdev->dev;
+       struct device_node *np = dev->of_node;
+
+       scpi_info = devm_kzalloc(dev, sizeof(*scpi_info), GFP_KERNEL);
+       if (!scpi_info)
+               return -ENOMEM;
+
+       if (of_match_device(legacy_scpi_of_match, &pdev->dev))
+               scpi_info->is_legacy = true;
+
+       count = of_count_phandle_with_args(np, "mboxes", "#mbox-cells");
+       if (count < 0) {
+               dev_err(dev, "no mboxes property in '%pOF'\n", np);
+               return -ENODEV;
+       }
+
+       scpi_chan = devm_kcalloc(dev, count, sizeof(*scpi_chan), GFP_KERNEL);
+       if (!scpi_chan)
+               return -ENOMEM;
+
+       for (idx = 0; idx < count; idx++) {
+               resource_size_t size;
+               struct scpi_chan *pchan = scpi_chan + idx;
+               struct mbox_client *cl = &pchan->cl;
+               struct device_node *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 SCPI payload mem 
resource\n");
+                       goto err;
+               }
+
+               size = resource_size(&res);
+               pchan->rx_payload = devm_ioremap(dev, res.start, size);
+               if (!pchan->rx_payload) {
+                       dev_err(dev, "failed to ioremap SCPI payload\n");
+                       ret = -EADDRNOTAVAIL;
+                       goto err;
+               }
+               pchan->tx_payload = pchan->rx_payload + (size >> 1);
+
+               cl->dev = dev;
+               cl->rx_callback = scpi_handle_remote_msg;
+               cl->tx_prepare = scpi_tx_prepare;
+               cl->tx_block = true;
+               cl->tx_tout = 20;
+               cl->knows_txdone = false; /* controller can't ack */
+
+               INIT_LIST_HEAD(&pchan->rx_pending);
+               INIT_LIST_HEAD(&pchan->xfers_list);
+               spin_lock_init(&pchan->rx_lock);
+               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);
+               }
+err:
+               scpi_free_channels(dev, scpi_chan, idx);
+               scpi_info = NULL;
+               return ret;
+       }
+
+       scpi_info->channels = scpi_chan;
+       scpi_info->num_chans = count;
+       scpi_info->commands = scpi_std_commands;
+
+       platform_set_drvdata(pdev, scpi_info);
+
+       if (scpi_info->is_legacy) {
+               /* Replace with legacy variants */
+               scpi_ops.clk_set_val = legacy_scpi_clk_set_val;
+               scpi_info->commands = scpi_legacy_commands;
+
+               /* Fill priority bitmap */
+               for (idx = 0; idx < ARRAY_SIZE(legacy_hpriority_cmds); idx++)
+                       set_bit(legacy_hpriority_cmds[idx],
+                               scpi_info->cmd_priority);
+       }
+
+       ret = scpi_init_versions(scpi_info);
+       if (ret) {
+               dev_err(dev, "incorrect or no SCP firmware found\n");
+               scpi_remove(pdev);
+               return ret;
+       }
+
+       _dev_info(dev, "SCP Protocol %d.%d Firmware %d.%d.%d version\n",
+                 PROTOCOL_REV_MAJOR(scpi_info->protocol_version),
+                 PROTOCOL_REV_MINOR(scpi_info->protocol_version),
+                 FW_REV_MAJOR(scpi_info->firmware_version),
+                 FW_REV_MINOR(scpi_info->firmware_version),
+                 FW_REV_PATCH(scpi_info->firmware_version));
+       scpi_info->scpi_ops = &scpi_ops;
+
+       ret = sysfs_create_groups(&dev->kobj, versions_groups);
+       if (ret)
+               dev_err(dev, "unable to create sysfs version group\n");
+
+       return of_platform_populate(dev->of_node, NULL, NULL, dev);
+}
+
+static const struct of_device_id scpi_of_match[] = {
+       {.compatible = "arm,scpi"},
+       {.compatible = "arm,scpi-pre-1.0"},
+       {},
+};
+
+MODULE_DEVICE_TABLE(of, scpi_of_match);
+
+static struct platform_driver scpi_driver = {
+       .driver = {
+               .name = "scpi_protocol",
+               .of_match_table = scpi_of_match,
+       },
+       .probe = scpi_probe,
+       .remove = scpi_remove,
+};
+module_platform_driver(scpi_driver);
+
+MODULE_AUTHOR("Sudeep Holla <sudeep.holla@xxxxxxx>");
+MODULE_DESCRIPTION("ARM SCPI mailbox protocol driver");
+MODULE_LICENSE("GPL v2");
diff --git a/xen/arch/arm/cpufreq/scpi_protocol.h 
b/xen/arch/arm/cpufreq/scpi_protocol.h
new file mode 100644
index 0000000..327d656
--- /dev/null
+++ b/xen/arch/arm/cpufreq/scpi_protocol.h
@@ -0,0 +1,84 @@
+/*
+ * SCPI Message Protocol driver header
+ *
+ * Copyright (C) 2014 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#include <linux/types.h>
+
+struct scpi_opp {
+       u32 freq;
+       u32 m_volt;
+} __packed;
+
+struct scpi_dvfs_info {
+       unsigned int count;
+       unsigned int latency; /* in nanoseconds */
+       struct scpi_opp *opps;
+};
+
+enum scpi_sensor_class {
+       TEMPERATURE,
+       VOLTAGE,
+       CURRENT,
+       POWER,
+       ENERGY,
+};
+
+struct scpi_sensor_info {
+       u16 sensor_id;
+       u8 class;
+       u8 trigger_type;
+       char name[20];
+} __packed;
+
+/**
+ * struct scpi_ops - represents the various operations provided
+ *     by SCP through SCPI message protocol
+ * @get_version: returns the major and minor revision on the SCPI
+ *     message protocol
+ * @clk_get_range: gets clock range limit(min - max in Hz)
+ * @clk_get_val: gets clock value(in Hz)
+ * @clk_set_val: sets the clock value, setting to 0 will disable the
+ *     clock (if supported)
+ * @dvfs_get_idx: gets the Operating Point of the given power domain.
+ *     OPP is an index to the list return by @dvfs_get_info
+ * @dvfs_set_idx: sets the Operating Point of the given power domain.
+ *     OPP is an index to the list return by @dvfs_get_info
+ * @dvfs_get_info: returns the DVFS capabilities of the given power
+ *     domain. It includes the OPP list and the latency information
+ */
+struct scpi_ops {
+       u32 (*get_version)(void);
+       int (*clk_get_range)(u16, unsigned long *, unsigned long *);
+       unsigned long (*clk_get_val)(u16);
+       int (*clk_set_val)(u16, unsigned long);
+       int (*dvfs_get_idx)(u8);
+       int (*dvfs_set_idx)(u8, u8);
+       struct scpi_dvfs_info *(*dvfs_get_info)(u8);
+       int (*device_domain_id)(struct device *);
+       int (*get_transition_latency)(struct device *);
+       int (*add_opps_to_device)(struct device *);
+       int (*sensor_get_capability)(u16 *sensors);
+       int (*sensor_get_info)(u16 sensor_id, struct scpi_sensor_info *);
+       int (*sensor_get_value)(u16, u64 *);
+       int (*device_get_power_state)(u16);
+       int (*device_set_power_state)(u16, u8);
+};
+
+#if IS_REACHABLE(CONFIG_ARM_SCPI_PROTOCOL)
+struct scpi_ops *get_scpi_ops(void);
+#else
+static inline struct scpi_ops *get_scpi_ops(void) { return NULL; }
+#endif
-- 
2.7.4


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