[RFC v2 5/8] xen/arm: introduce SCMI-SMC mediator driver

[Oleksii Moisieiev <Oleksii_Moisieiev@epam.com>]

This is the implementation of SCI interface, called SCMI-SMC driver,
which works as the mediator between XEN Domains and Firmware (SCP, ATF etc).
This allows devices from the Domains to work with clocks, resets and
power-domains without access to CPG.

Originally, cpg should be passed to the domain so it can work with
power-domains/clocks/resets etc. Considering that cpg can't be split between
the Domains, we get the limitation that the devices, which are using
power-domains/clocks/resets etc, couldn't be split between the domains.
The solution is to move the power-domain/clock/resets etc to the
Firmware (such as SCP firmware or ATF) and provide interface for the
Domains. XEN should have an entity, caled SCI-Mediator, which is
responsible for messages redirection between Domains and Firmware and
for permission handling.

The following features are implemented:
- request SCMI channels from ATF and pass channels to Domains;
- set device permissions for Domains based on the Domain partial
device-tree. Devices with permissions are able to work with clocks,
resets and power-domains via SCMI;
- redirect scmi messages from Domains to ATF.

Signed-off-by: Oleksii Moisieiev <oleksii_moisieiev@epam.com>
---
 xen/arch/arm/Kconfig        |   2 +
 xen/arch/arm/sci/Kconfig    |  10 +
 xen/arch/arm/sci/scmi_smc.c | 959 ++++++++++++++++++++++++++++++++++++
 3 files changed, 971 insertions(+)
 create mode 100644 xen/arch/arm/sci/Kconfig
 create mode 100644 xen/arch/arm/sci/scmi_smc.c

diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
index ab07833582..3b0dfc57b6 100644
--- a/xen/arch/arm/Kconfig
+++ b/xen/arch/arm/Kconfig
@@ -123,6 +123,8 @@ config ARM_SCI
 	  support. It allows guests to control system resourcess via one of
 	  ARM_SCI mediators implemented in XEN.
 
+	source "arch/arm/sci/Kconfig"
+
 endmenu
 
 menu "ARM errata workaround via the alternative framework"
diff --git a/xen/arch/arm/sci/Kconfig b/xen/arch/arm/sci/Kconfig
new file mode 100644
index 0000000000..10b634d2ed
--- /dev/null
+++ b/xen/arch/arm/sci/Kconfig
@@ -0,0 +1,10 @@
+config SCMI_SMC
+	bool "Enable SCMI-SMC mediator driver"
+	default n
+	depends on ARM_SCI && HOST_DTB_EXPORT
+	---help---
+
+	Enables mediator in XEN to pass SCMI requests from Domains to ATF.
+	This feature allows drivers from Domains to work with System
+	Controllers (such as power,resets,clock etc.). SCP is used as transport
+	for communication.
diff --git a/xen/arch/arm/sci/scmi_smc.c b/xen/arch/arm/sci/scmi_smc.c
new file mode 100644
index 0000000000..103529dfab
--- /dev/null
+++ b/xen/arch/arm/sci/scmi_smc.c
@@ -0,0 +1,959 @@
+/*
+ * xen/arch/arm/sci/scmi_smc.c
+ *
+ * SCMI mediator driver, using SCP as transport.
+ *
+ * Oleksii Moisieiev <oleksii_moisieiev@epam.com>
+ * Copyright (C) 2021, EPAM Systems.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that 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.
+ */
+
+#include <asm/sci/sci.h>
+#include <asm/smccc.h>
+#include <asm/io.h>
+#include <xen/bitops.h>
+#include <xen/config.h>
+#include <xen/sched.h>
+#include <xen/device_tree.h>
+#include <xen/iocap.h>
+#include <xen/init.h>
+#include <xen/err.h>
+#include <xen/lib.h>
+#include <xen/list.h>
+#include <xen/mm.h>
+#include <xen/string.h>
+#include <xen/time.h>
+#include <xen/vmap.h>
+
+#define SCMI_BASE_PROTOCOL                  0x10
+#define SCMI_BASE_PROTOCOL_ATTIBUTES        0x1
+#define SCMI_BASE_SET_DEVICE_PERMISSIONS    0x9
+#define SCMI_BASE_RESET_AGENT_CONFIGURATION 0xB
+#define SCMI_BASE_DISCOVER_AGENT            0x7
+
+/* SCMI return codes. See section 4.1.4 of SCMI spec (DEN0056C) */
+#define SCMI_SUCCESS              0
+#define SCMI_NOT_SUPPORTED      (-1)
+#define SCMI_INVALID_PARAMETERS (-2)
+#define SCMI_DENIED             (-3)
+#define SCMI_NOT_FOUND          (-4)
+#define SCMI_OUT_OF_RANGE       (-5)
+#define SCMI_BUSY               (-6)
+#define SCMI_COMMS_ERROR        (-7)
+#define SCMI_GENERIC_ERROR      (-8)
+#define SCMI_HARDWARE_ERROR     (-9)
+#define SCMI_PROTOCOL_ERROR     (-10)
+
+#define DT_MATCH_SCMI_SMC DT_MATCH_COMPATIBLE("arm,scmi-smc")
+
+#define SCMI_SMC_ID                        "arm,smc-id"
+#define SCMI_SHARED_MEMORY                 "arm,scmi-shmem"
+#define SCMI_SHMEM                         "shmem"
+#define SCMI_SHMEM_MAPPED_SIZE             PAGE_SIZE
+
+#define HYP_CHANNEL                          0x0
+
+#define HDR_ID                             GENMASK(7,0)
+#define HDR_TYPE                           GENMASK(9, 8)
+#define HDR_PROTO                          GENMASK(17, 10)
+
+/* SCMI protocol, refer to section 4.2.2.2 (DEN0056C) */
+#define MSG_N_AGENTS_MASK                  GENMASK(15, 8)
+
+#define FIELD_GET(_mask, _reg)\
+    ((typeof(_mask))(((_reg) & (_mask)) >> (ffs64(_mask) - 1)))
+#define FIELD_PREP(_mask, _val)\
+    (((typeof(_mask))(_val) << (ffs64(_mask) - 1)) & (_mask))
+
+typedef struct scmi_msg_header {
+    uint8_t id;
+    uint8_t type;
+    uint8_t protocol;
+} scmi_msg_header_t;
+
+#define SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE   BIT(0, UL)
+#define SCMI_SHMEM_CHAN_STAT_CHANNEL_ERROR  BIT(1, UL)
+
+#define SCMI_ALLOW_ACCESS                   BIT(0, UL)
+
+struct scmi_shared_mem {
+    uint32_t reserved;
+    uint32_t channel_status;
+    uint32_t reserved1[2];
+    uint32_t flags;
+    uint32_t length;
+    uint32_t msg_header;
+    uint8_t msg_payload[];
+};
+
+struct dt_channel_addr {
+    u64 addr;
+    u64 size;
+    struct list_head list;
+};
+
+struct scmi_channel {
+    int chan_id;
+    int agent_id;
+    uint32_t func_id;
+    domid_t domain_id;
+    uint64_t paddr;
+    uint64_t len;
+    struct scmi_shared_mem *shmem;
+    spinlock_t lock;
+    struct list_head list;
+};
+
+struct scmi_data {
+    struct list_head channel_list;
+    spinlock_t channel_list_lock;
+    bool initialized;
+};
+
+static struct scmi_data scmi_data;
+
+
+/*
+ * pack_scmi_header() - packs and returns 32-bit header
+ *
+ * @hdr: pointer to header containing all the information on message id,
+ *    protocol id and type id.
+ *
+ * Return: 32-bit packed message header to be sent to the platform.
+ */
+static inline uint32_t pack_scmi_header(scmi_msg_header_t *hdr)
+{
+    return FIELD_PREP(HDR_ID, hdr->id) |
+        FIELD_PREP(HDR_TYPE, hdr->type) |
+        FIELD_PREP(HDR_PROTO, hdr->protocol);
+}
+
+/*
+ * unpack_scmi_header() - unpacks and records message and protocol id
+ *
+ * @msg_hdr: 32-bit packed message header sent from the platform
+ * @hdr: pointer to header to fetch message and protocol id.
+ */
+static inline void unpack_scmi_header(uint32_t msg_hdr, scmi_msg_header_t *hdr)
+{
+    hdr->id = FIELD_GET(HDR_ID, msg_hdr);
+    hdr->type = FIELD_GET(HDR_TYPE, msg_hdr);
+    hdr->protocol = FIELD_GET(HDR_PROTO, msg_hdr);
+}
+
+static inline int channel_is_free(struct scmi_channel *chan_info)
+{
+    return ( chan_info->shmem->channel_status
+            & SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE ) ? 0 : -EBUSY;
+}
+
+/*
+ * Copy data from IO memory space to "real" memory space.
+ */
+void __memcpy_fromio(void *to, const volatile void __iomem *from, size_t count)
+{
+    while (count && !IS_ALIGNED((unsigned long)from, 4)) {
+        *(u8 *)to = __raw_readb(from);
+        from++;
+        to++;
+        count--;
+    }
+
+    while (count >= 4) {
+        *(u32 *)to = __raw_readl(from);
+        from += 4;
+        to += 4;
+        count -= 4;
+    }
+
+    while (count) {
+        *(u8 *)to = __raw_readb(from);
+        from++;
+        to++;
+        count--;
+    }
+}
+
+/*
+ * Copy data from "real" memory space to IO memory space.
+ */
+void __memcpy_toio(volatile void __iomem *to, const void *from, size_t count)
+{
+    while (count && !IS_ALIGNED((unsigned long)to, 4)) {
+        __raw_writeb(*(u8 *)from, to);
+        from++;
+        to++;
+        count--;
+    }
+
+    while (count >= 4) {
+        __raw_writel(*(u32 *)from, to);
+        from += 4;
+        to += 4;
+        count -= 4;
+    }
+
+    while (count) {
+        __raw_writeb(*(u8 *)from, to);
+        from++;
+        to++;
+        count--;
+    }
+}
+
+static int send_smc_message(struct scmi_channel *chan_info,
+                            scmi_msg_header_t *hdr, void *data, int len)
+{
+    struct arm_smccc_res resp;
+    int ret;
+
+    if ( (len + sizeof(chan_info->shmem->msg_header)) >
+                         SCMI_SHMEM_MAPPED_SIZE )
+    {
+        printk(XENLOG_ERR
+               "scmi: Wrong size of smc message. Data is invalid\n");
+        return -EINVAL;
+    }
+
+    printk(XENLOG_DEBUG "scmi: status =%d len=%d\n",
+           chan_info->shmem->channel_status, len);
+    printk(XENLOG_DEBUG "scmi: header id = %d type = %d, proto = %d\n",
+           hdr->id, hdr->type, hdr->protocol);
+
+    ret = channel_is_free(chan_info);
+    if ( IS_ERR_VALUE(ret) )
+        return ret;
+
+    chan_info->shmem->channel_status = 0x0;
+    /* Writing 0x0 right now, but SCMI_SHMEM_FLAG_INTR_ENABLED can be set */
+    chan_info->shmem->flags = 0x0;
+    chan_info->shmem->length = sizeof(chan_info->shmem->msg_header) + len;
+    chan_info->shmem->msg_header = pack_scmi_header(hdr);
+
+    printk(XENLOG_DEBUG "scmi: Writing to shmem address %p\n",
+           chan_info->shmem);
+    if ( len > 0 && data )
+        __memcpy_toio((void *)(chan_info->shmem->msg_payload), data, len);
+
+    arm_smccc_smc(chan_info->func_id, 0, 0, 0, 0, 0, 0, chan_info->chan_id,
+                  &resp);
+
+    printk(XENLOG_DEBUG "scmi: scmccc_smc response %d\n", (int)(resp.a0));
+
+    if ( resp.a0 )
+        return -EOPNOTSUPP;
+
+    return 0;
+}
+
+static int check_scmi_status(int scmi_status)
+{
+    if ( scmi_status == SCMI_SUCCESS )
+        return 0;
+
+    printk(XENLOG_DEBUG "scmi: Error received: %d\n", scmi_status);
+
+    switch ( scmi_status )
+    {
+    case SCMI_NOT_SUPPORTED:
+        return -EOPNOTSUPP;
+    case SCMI_INVALID_PARAMETERS:
+        return -EINVAL;
+    case SCMI_DENIED:
+        return -EACCES;
+    case SCMI_NOT_FOUND:
+        return -ENOENT;
+    case SCMI_OUT_OF_RANGE:
+        return -ERANGE;
+    case SCMI_BUSY:
+        return -EBUSY;
+    case SCMI_COMMS_ERROR:
+        return -ENOTCONN;
+    case SCMI_GENERIC_ERROR:
+        return -EIO;
+    case SCMI_HARDWARE_ERROR:
+        return -ENXIO;
+    case SCMI_PROTOCOL_ERROR:
+        return -EBADMSG;
+    default:
+        return -EINVAL;
+    }
+}
+
+static int get_smc_response(struct scmi_channel *chan_info,
+                            scmi_msg_header_t *hdr, void *data, int len)
+{
+    int recv_len;
+    int ret;
+
+    printk(XENLOG_DEBUG "scmi: get smc responce msgid %d\n", hdr->id);
+
+    if ( len >= SCMI_SHMEM_MAPPED_SIZE - sizeof(chan_info->shmem) )
+    {
+        printk(XENLOG_ERR
+               "scmi: Wrong size of input smc message. Data may be invalid\n");
+        return -EINVAL;
+    }
+
+    ret = channel_is_free(chan_info);
+    if ( IS_ERR_VALUE(ret) )
+        return ret;
+
+    recv_len = chan_info->shmem->length - sizeof(chan_info->shmem->msg_header);
+
+    if ( recv_len < 0 )
+    {
+        printk(XENLOG_ERR
+               "scmi: Wrong size of smc message. Data may be invalid\n");
+        return -EINVAL;
+    }
+
+    if ( recv_len > len )
+    {
+        printk(XENLOG_ERR
+               "scmi: Not enough buffer for message %d, expecting %d\n",
+               recv_len, len);
+        return -EINVAL;
+    }
+
+    unpack_scmi_header(chan_info->shmem->msg_header, hdr);
+
+    if ( recv_len > 0 )
+    {
+        __memcpy_fromio(data, chan_info->shmem->msg_payload, recv_len);
+    }
+
+    return 0;
+}
+
+static int do_smc_xfer(struct scmi_channel *channel, scmi_msg_header_t *hdr, void *tx_data, int tx_size,
+                       void *rx_data, int rx_size)
+{
+    int ret = 0;
+
+    ASSERT( channel && channel->shmem);
+
+    if ( !hdr )
+        return -EINVAL;
+
+    spin_lock(&channel->lock);
+
+    ret = send_smc_message(channel, hdr, tx_data, tx_size);
+    if ( ret )
+        goto clean;
+
+    ret = get_smc_response(channel, hdr, rx_data, rx_size);
+clean:
+    spin_unlock(&channel->lock);
+
+    return ret;
+}
+
+static struct scmi_channel *get_channel_by_id(uint8_t chan_id)
+{
+    struct scmi_channel *curr;
+    bool found = false;
+
+    spin_lock(&scmi_data.channel_list_lock);
+    list_for_each_entry(curr, &scmi_data.channel_list, list)
+    {
+        if ( curr->chan_id == chan_id )
+        {
+            found = true;
+            break;
+        }
+    }
+
+    spin_unlock(&scmi_data.channel_list_lock);
+    if ( found )
+        return curr;
+
+    return NULL;
+}
+
+static struct scmi_channel *aquire_scmi_channel(domid_t domain_id)
+{
+    struct scmi_channel *curr;
+    bool found = false;
+
+    ASSERT(domain_id != DOMID_INVALID && domain_id >= 0);
+
+    spin_lock(&scmi_data.channel_list_lock);
+    list_for_each_entry(curr, &scmi_data.channel_list, list)
+    {
+        if ( curr->domain_id == DOMID_INVALID )
+        {
+            curr->domain_id = domain_id;
+            found = true;
+            break;
+        }
+    }
+
+    spin_unlock(&scmi_data.channel_list_lock);
+    if ( found )
+        return curr;
+
+    return NULL;
+}
+
+static void relinquish_scmi_channel(struct scmi_channel *channel)
+{
+    ASSERT(channel != NULL);
+
+    spin_lock(&scmi_data.channel_list_lock);
+    channel->domain_id = DOMID_INVALID;
+    spin_unlock(&scmi_data.channel_list_lock);
+}
+
+static int map_channel_memory(struct scmi_channel *channel)
+{
+    ASSERT( channel && channel->paddr );
+    channel->shmem = ioremap_cache(channel->paddr, SCMI_SHMEM_MAPPED_SIZE);
+    if ( !channel->shmem )
+        return -ENOMEM;
+
+    channel->shmem->channel_status = SCMI_SHMEM_CHAN_STAT_CHANNEL_FREE;
+    printk(XENLOG_DEBUG "scmi: Got shmem after vmap %p\n", channel->shmem);
+    return 0;
+}
+
+static void unmap_channel_memory(struct scmi_channel *channel)
+{
+    ASSERT( channel && channel->shmem );
+    iounmap(channel->shmem);
+    channel->shmem = NULL;
+}
+
+static struct scmi_channel *smc_create_channel(uint8_t chan_id,
+                                               uint32_t func_id, uint64_t addr)
+{
+    struct scmi_channel *channel;
+
+    channel = get_channel_by_id(chan_id);
+    if ( channel )
+        return ERR_PTR(EEXIST);
+
+    channel = xmalloc(struct scmi_channel);
+    if ( !channel )
+        return ERR_PTR(ENOMEM);
+
+    channel->chan_id = chan_id;
+    channel->func_id = func_id;
+    channel->domain_id = DOMID_INVALID;
+    channel->shmem = NULL;
+    channel->paddr = addr;
+    spin_lock_init(&channel->lock);
+    spin_lock(&scmi_data.channel_list_lock);
+    list_add(&channel->list, &scmi_data.channel_list);
+    spin_unlock(&scmi_data.channel_list_lock);
+    return channel;
+}
+
+static int mem_permit_access(struct domain *d, uint64_t addr, uint64_t len)
+{
+    return iomem_permit_access(d, paddr_to_pfn(addr),
+                paddr_to_pfn(PAGE_ALIGN(addr + len -1)));
+}
+
+static int mem_deny_access(struct domain *d, uint64_t addr,
+                                     uint64_t len)
+{
+    return iomem_deny_access(d, paddr_to_pfn(addr),
+                paddr_to_pfn(PAGE_ALIGN(addr + len -1)));
+}
+
+static int dt_update_domain_range(uint64_t addr, uint64_t size)
+{
+    struct dt_device_node *shmem_node;
+    __be32 *hw_reg;
+    const struct dt_property *pp;
+    uint32_t len;
+
+    shmem_node = dt_find_compatible_node(NULL, NULL, SCMI_SHARED_MEMORY);
+    if ( !shmem_node )
+    {
+        printk(XENLOG_ERR "scmi: Unable to find %s node in DT\n", SCMI_SHMEM);
+        return -EINVAL;
+    }
+
+    pp = dt_find_property(shmem_node, "reg", &len);
+    if ( !pp )
+    {
+        printk(XENLOG_ERR "scmi: Unable to find regs entry in shmem node\n");
+        return -ENOENT;
+    }
+
+    hw_reg = pp->value;
+    dt_set_range(&hw_reg, shmem_node, addr, size);
+
+    return 0;
+}
+
+static void free_channel_list(void)
+{
+    struct scmi_channel *curr, *_curr;
+
+    spin_lock(&scmi_data.channel_list_lock);
+    list_for_each_entry_safe (curr, _curr, &scmi_data.channel_list, list)
+    {
+        list_del(&curr->list);
+        xfree(curr);
+    }
+
+    spin_unlock(&scmi_data.channel_list_lock);
+}
+
+static struct dt_device_node *get_dt_node_from_property(
+                struct dt_device_node *node, const char * p_name)
+{
+    const __be32 *prop;
+
+    ASSERT( node );
+
+    prop = dt_get_property(node, p_name, NULL);
+    if ( !prop )
+        return ERR_PTR(-EINVAL);
+
+    return dt_find_node_by_phandle(be32_to_cpup(prop));
+}
+
+static int get_shmem_regions(struct list_head *head, u64 hyp_addr)
+{
+    struct dt_device_node *node;
+    int ret;
+    struct dt_channel_addr *lchan;
+    u64 laddr, lsize;
+
+    node = dt_find_compatible_node(NULL, NULL, SCMI_SHARED_MEMORY);
+    if ( !node )
+        return -ENOENT;
+
+    while ( node )
+    {
+        ret = dt_device_get_address(node, 0, &laddr, &lsize);
+        if ( ret )
+            return ret;
+
+        if ( laddr != hyp_addr )
+        {
+            lchan = xmalloc(struct dt_channel_addr);
+            if ( !lchan )
+                return -ENOMEM;
+            lchan->addr = laddr;
+            lchan->size = lsize;
+
+            list_add_tail(&lchan->list, head);
+        }
+
+        node = dt_find_compatible_node(node, NULL, SCMI_SHARED_MEMORY);
+    }
+
+    return 0;
+}
+
+static int read_hyp_channel_addr(struct dt_device_node *scmi_node,
+                                 u64 *addr, u64 *size)
+{
+    struct dt_device_node *shmem_node;
+    shmem_node = get_dt_node_from_property(scmi_node, "shmem");
+    if ( IS_ERR_OR_NULL(shmem_node) )
+    {
+        printk(XENLOG_ERR
+               "scmi: Device tree error, can't parse reserved memory %ld\n",
+               PTR_ERR(shmem_node));
+        return PTR_ERR(shmem_node);
+    }
+
+    return dt_device_get_address(shmem_node, 0, addr, size);
+}
+
+static void free_shmem_regions(struct list_head *addr_list)
+{
+    struct dt_channel_addr *curr, *_curr;
+
+    list_for_each_entry_safe (curr, _curr, addr_list, list)
+    {
+        list_del(&curr->list);
+        xfree(curr);
+    }
+}
+
+static __init bool scmi_probe(struct dt_device_node *scmi_node)
+{
+    u64 addr, size;
+    int ret, i;
+    struct scmi_channel *channel, *agent_channel;
+    int n_agents;
+    scmi_msg_header_t hdr;
+    struct rx_t {
+        int32_t status;
+        uint32_t attributes;
+    } rx;
+    struct dt_channel_addr *entry;
+    struct list_head addr_list;
+
+    uint32_t func_id;
+
+    ASSERT(scmi_node != NULL);
+
+    INIT_LIST_HEAD(&scmi_data.channel_list);
+    spin_lock_init(&scmi_data.channel_list_lock);
+
+    if ( !dt_property_read_u32(scmi_node, SCMI_SMC_ID, &func_id) )
+    {
+        printk(XENLOG_ERR "scmi: Unable to read smc-id from DT\n");
+        return false;
+    }
+
+    ret = read_hyp_channel_addr(scmi_node, &addr, &size);
+    if ( IS_ERR_VALUE(ret) )
+        return false;
+
+    if ( !IS_ALIGNED(size, SCMI_SHMEM_MAPPED_SIZE) )
+    {
+        printk(XENLOG_ERR "scmi: Reserved memory is not aligned\n");
+        return false;
+    }
+
+    INIT_LIST_HEAD(&addr_list);
+
+    ret = get_shmem_regions(&addr_list, addr);
+    if ( IS_ERR_VALUE(ret) )
+        goto out;
+
+    channel = smc_create_channel(HYP_CHANNEL, func_id, addr);
+    if ( IS_ERR(channel) )
+        goto out;
+
+    ret = map_channel_memory(channel);
+    if ( ret )
+        goto out;
+
+    spin_lock(&scmi_data.channel_list_lock);
+    channel->domain_id = DOMID_XEN;
+    spin_unlock(&scmi_data.channel_list_lock);
+
+    hdr.id = SCMI_BASE_PROTOCOL_ATTIBUTES;
+    hdr.type = 0;
+    hdr.protocol = SCMI_BASE_PROTOCOL;
+
+    ret = do_smc_xfer(channel, &hdr, NULL, 0, &rx, sizeof(rx));
+    if ( ret )
+        goto error;
+
+    ret = check_scmi_status(rx.status);
+    if ( ret )
+        goto error;
+
+    n_agents = FIELD_GET(MSG_N_AGENTS_MASK, rx.attributes);
+    printk(XENLOG_DEBUG "scmi: Got agent count %d\n", n_agents);
+
+    i = 1;
+    list_for_each_entry(entry, &addr_list, list)
+    {
+        uint32_t tx_agent_id = 0xFFFFFFFF;
+        struct {
+            int32_t status;
+            uint32_t agent_id;
+            char name[16];
+        } da_rx;
+
+        agent_channel = smc_create_channel(i, func_id,
+                                           entry->addr);
+        if ( IS_ERR(agent_channel) )
+        {
+            ret = PTR_ERR(agent_channel);
+            goto error;
+        }
+
+        ret = map_channel_memory(agent_channel);
+        if ( ret )
+            goto error;
+
+        hdr.id = SCMI_BASE_DISCOVER_AGENT;
+        hdr.type = 0;
+        hdr.protocol = SCMI_BASE_PROTOCOL;
+
+        ret = do_smc_xfer(agent_channel, &hdr, &tx_agent_id,
+                          sizeof(tx_agent_id), &da_rx, sizeof(da_rx));
+        if ( ret )
+        {
+            unmap_channel_memory(agent_channel);
+            goto error;
+        }
+
+        unmap_channel_memory(agent_channel);
+
+        ret = check_scmi_status(da_rx.status);
+        if ( ret )
+            goto error;
+
+        printk(XENLOG_DEBUG "scmi: status=0x%x id=0x%x name=%s\n",
+                da_rx.status, da_rx.agent_id, da_rx.name);
+
+        agent_channel->agent_id = da_rx.agent_id;
+
+        if ( i == n_agents )
+            break;
+
+        i++;
+    }
+
+    scmi_data.initialized = true;
+    goto out;
+
+error:
+    unmap_channel_memory(channel);
+    free_channel_list();
+out:
+    free_shmem_regions(&addr_list);
+    return ret == 0;
+}
+
+static int scmi_domain_init(struct domain *d,
+                           struct xen_arch_domainconfig *config)
+{
+    struct scmi_channel *channel;
+    int ret;
+
+    if ( !scmi_data.initialized )
+        return 0;
+
+    printk(XENLOG_INFO "scmi: domain_id = %d\n", d->domain_id);
+
+    channel = aquire_scmi_channel(d->domain_id);
+    if ( IS_ERR_OR_NULL(channel) )
+        return -ENOENT;
+
+#ifdef CONFIG_ARM_32
+    printk(XENLOG_INFO
+           "scmi: Aquire SCMI channel id = 0x%x , domain_id = %d paddr = 0x%llx\n",
+           channel->chan_id, channel->domain_id, channel->paddr);
+#else
+    printk(XENLOG_INFO
+           "scmi: Aquire SCMI channel id = 0x%x , domain_id = %d paddr = 0x%lx\n",
+           channel->chan_id, channel->domain_id, channel->paddr);
+#endif
+
+    if ( is_hardware_domain(d) )
+    {
+        ret = mem_permit_access(d, channel->paddr, PAGE_SIZE);
+        if ( IS_ERR_VALUE(ret) )
+            goto error;
+
+        ret = dt_update_domain_range(channel->paddr, PAGE_SIZE);
+        if ( IS_ERR_VALUE(ret) )
+        {
+            int rc = mem_deny_access(d, channel->paddr, PAGE_SIZE);
+            if ( rc )
+                printk(XENLOG_ERR "Unable to mem_deny_access\n");
+
+            goto error;
+        }
+    }
+
+    d->arch.sci = channel;
+    if ( config )
+        config->arm_sci_agent_paddr = channel->paddr;
+
+    return 0;
+error:
+    relinquish_scmi_channel(channel);
+
+    return ret;
+}
+
+static int scmi_add_device_by_devid(struct domain *d, uint32_t scmi_devid)
+{
+    struct scmi_channel *channel, *agent_channel;
+    scmi_msg_header_t hdr;
+    struct scmi_perms_tx {
+        uint32_t agent_id;
+        uint32_t device_id;
+        uint32_t flags;
+    } tx;
+    struct rx_t {
+        int32_t status;
+        uint32_t attributes;
+    } rx;
+    int ret;
+
+    if ( !scmi_data.initialized )
+        return 0;
+
+    printk(XENLOG_DEBUG "scmi: scmi_devid = %d\n", scmi_devid);
+
+    agent_channel = d->arch.sci;
+    if ( IS_ERR_OR_NULL(agent_channel) )
+        return PTR_ERR(agent_channel);
+
+    channel = get_channel_by_id(HYP_CHANNEL);
+    if ( IS_ERR_OR_NULL(channel) )
+        return PTR_ERR(channel);
+
+    hdr.id = SCMI_BASE_SET_DEVICE_PERMISSIONS;
+    hdr.type = 0;
+    hdr.protocol = SCMI_BASE_PROTOCOL;
+
+    tx.agent_id = agent_channel->agent_id;
+    tx.device_id = scmi_devid;
+    tx.flags = SCMI_ALLOW_ACCESS;
+
+    ret = do_smc_xfer(channel, &hdr, &tx, sizeof(tx), &rx, sizeof(&rx));
+    if ( IS_ERR_VALUE(ret) )
+        return ret;
+
+    ret = check_scmi_status(rx.status);
+    if ( IS_ERR_VALUE(ret) )
+        return ret;
+
+    return 0;
+}
+
+static int scmi_add_dt_device(struct domain *d, struct dt_device_node *dev)
+{
+    uint32_t scmi_devid;
+
+    if ( (!scmi_data.initialized) || (!d->arch.sci) )
+        return 0;
+
+    if ( !dt_property_read_u32(dev, "scmi_devid", &scmi_devid) )
+        return 0;
+
+    printk(XENLOG_INFO "scmi: dt_node = %s\n", dt_node_full_name(dev));
+
+    return scmi_add_device_by_devid(d, scmi_devid);
+}
+
+static int scmi_relinquish_resources(struct domain *d)
+{
+    int ret;
+    struct scmi_channel *channel, *agent_channel;
+    scmi_msg_header_t hdr;
+    struct reset_agent_tx {
+        uint32_t agent_id;
+        uint32_t flags;
+    } tx;
+    uint32_t rx;
+
+    if ( !d->arch.sci )
+        return 0;
+
+    agent_channel = d->arch.sci;
+
+    spin_lock(&agent_channel->lock);
+    tx.agent_id = agent_channel->agent_id;
+    spin_unlock(&agent_channel->lock);
+
+    channel = get_channel_by_id(HYP_CHANNEL);
+    if ( !channel )
+    {
+        printk(XENLOG_ERR
+               "scmi: Unable to get Hypervisor scmi channel for domain %d\n",
+               d->domain_id);
+        return -EINVAL;
+    }
+
+    hdr.id = SCMI_BASE_RESET_AGENT_CONFIGURATION;
+    hdr.type = 0;
+    hdr.protocol = SCMI_BASE_PROTOCOL;
+
+    tx.flags = 0;
+
+    ret = do_smc_xfer(channel, &hdr, &tx, sizeof(tx), &rx, sizeof(rx));
+    if ( ret )
+        return ret;
+
+    ret = check_scmi_status(rx);
+
+    return ret;
+}
+
+static void scmi_domain_destroy(struct domain *d)
+{
+    struct scmi_channel *channel;
+
+    if ( !d->arch.sci )
+        return;
+
+    channel = d->arch.sci;
+    spin_lock(&channel->lock);
+
+    relinquish_scmi_channel(channel);
+    printk(XENLOG_DEBUG "scmi: Free domain %d\n", d->domain_id);
+
+    d->arch.sci = NULL;
+
+    mem_deny_access(d, channel->paddr, PAGE_SIZE);
+    spin_unlock(&channel->lock);
+}
+
+static bool scmi_handle_call(struct domain *d, void *args)
+{
+    bool res = false;
+    struct scmi_channel *agent_channel;
+    struct arm_smccc_res resp;
+    struct cpu_user_regs *regs = args;
+
+    if ( !d->arch.sci )
+        return false;
+
+    agent_channel = d->arch.sci;
+    spin_lock(&agent_channel->lock);
+
+    if ( agent_channel->func_id != regs->r0 )
+    {
+        res = false;
+        goto unlock;
+    }
+
+    arm_smccc_smc(agent_channel->func_id, 0, 0, 0, 0, 0, 0,
+                  agent_channel->chan_id, &resp);
+
+    set_user_reg(regs, 0, resp.a0);
+    set_user_reg(regs, 1, resp.a1);
+    set_user_reg(regs, 2, resp.a2);
+    set_user_reg(regs, 3, resp.a3);
+    res = true;
+unlock:
+    spin_unlock(&agent_channel->lock);
+
+    return res;
+}
+
+static const struct dt_device_match scmi_smc_match[] __initconst =
+{
+    DT_MATCH_SCMI_SMC,
+    { /* sentinel */ },
+};
+
+static const struct sci_mediator_ops scmi_ops =
+{
+    .probe = scmi_probe,
+    .domain_init = scmi_domain_init,
+    .domain_destroy = scmi_domain_destroy,
+    .add_dt_device = scmi_add_dt_device,
+    .relinquish_resources = scmi_relinquish_resources,
+    .handle_call = scmi_handle_call,
+};
+
+REGISTER_SCI_MEDIATOR(scmi_smc, "SCMI-SMC", XEN_DOMCTL_CONFIG_ARM_SCI_SCMI_SMC,
+                      scmi_smc_match, &scmi_ops);
+
+/*
+ * Local variables:
+ * mode: C
+ * c-file-style: "BSD"
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
-- 
2.27.0