diff --git a/drivers/arm/css/scpi/css_scpi.c b/drivers/arm/css/scpi/css_scpi.c
new file mode 100644
index 0000000..4b73265
--- /dev/null
+++ b/drivers/arm/css/scpi/css_scpi.c
@@ -0,0 +1,262 @@
+/*
+ * Copyright (c) 2014-2018, ARM Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <assert.h>
+#include <string.h>
+
+#include <arch_helpers.h>
+#include <common/debug.h>
+#include <drivers/arm/css/css_mhu.h>
+#include <drivers/arm/css/css_scpi.h>
+#include <lib/utils.h>
+#include <plat/common/platform.h>
+#include <platform_def.h>
+
+#define SCPI_SHARED_MEM_SCP_TO_AP	PLAT_CSS_SCP_COM_SHARED_MEM_BASE
+#define SCPI_SHARED_MEM_AP_TO_SCP	(PLAT_CSS_SCP_COM_SHARED_MEM_BASE \
+								 + 0x100)
+
+/* Header and payload addresses for commands from AP to SCP */
+#define SCPI_CMD_HEADER_AP_TO_SCP		\
+	((scpi_cmd_t *) SCPI_SHARED_MEM_AP_TO_SCP)
+#define SCPI_CMD_PAYLOAD_AP_TO_SCP		\
+	((void *) (SCPI_SHARED_MEM_AP_TO_SCP + sizeof(scpi_cmd_t)))
+
+/* Header and payload addresses for responses from SCP to AP */
+#define SCPI_RES_HEADER_SCP_TO_AP \
+	((scpi_cmd_t *) SCPI_SHARED_MEM_SCP_TO_AP)
+#define SCPI_RES_PAYLOAD_SCP_TO_AP \
+	((void *) (SCPI_SHARED_MEM_SCP_TO_AP + sizeof(scpi_cmd_t)))
+
+/* ID of the MHU slot used for the SCPI protocol */
+#define SCPI_MHU_SLOT_ID		0
+
+static void scpi_secure_message_start(void)
+{
+	mhu_secure_message_start(SCPI_MHU_SLOT_ID);
+}
+
+static void scpi_secure_message_send(size_t payload_size)
+{
+	/*
+	 * Ensure that any write to the SCPI payload area is seen by SCP before
+	 * we write to the MHU register. If these 2 writes were reordered by
+	 * the CPU then SCP would read stale payload data
+	 */
+	dmbst();
+
+	mhu_secure_message_send(SCPI_MHU_SLOT_ID);
+}
+
+static void scpi_secure_message_receive(scpi_cmd_t *cmd)
+{
+	uint32_t mhu_status;
+
+	assert(cmd != NULL);
+
+	mhu_status = mhu_secure_message_wait();
+
+	/* Expect an SCPI message, reject any other protocol */
+	if (mhu_status != (1 << SCPI_MHU_SLOT_ID)) {
+		ERROR("MHU: Unexpected protocol (MHU status: 0x%x)\n",
+			mhu_status);
+		panic();
+	}
+
+	/*
+	 * Ensure that any read to the SCPI payload area is done after reading
+	 * the MHU register. If these 2 reads were reordered then the CPU would
+	 * read invalid payload data
+	 */
+	dmbld();
+
+	memcpy(cmd, (void *) SCPI_SHARED_MEM_SCP_TO_AP, sizeof(*cmd));
+}
+
+static void scpi_secure_message_end(void)
+{
+	mhu_secure_message_end(SCPI_MHU_SLOT_ID);
+}
+
+int scpi_wait_ready(void)
+{
+	scpi_cmd_t scpi_cmd;
+
+	VERBOSE("Waiting for SCP_READY command...\n");
+
+	/* Get a message from the SCP */
+	scpi_secure_message_start();
+	scpi_secure_message_receive(&scpi_cmd);
+	scpi_secure_message_end();
+
+	/* We are expecting 'SCP Ready', produce correct error if it's not */
+	scpi_status_t status = SCP_OK;
+	if (scpi_cmd.id != SCPI_CMD_SCP_READY) {
+		ERROR("Unexpected SCP command: expected command #%u, got command #%u\n",
+		      SCPI_CMD_SCP_READY, scpi_cmd.id);
+		status = SCP_E_SUPPORT;
+	} else if (scpi_cmd.size != 0) {
+		ERROR("SCP_READY command has incorrect size: expected 0, got %u\n",
+		      scpi_cmd.size);
+		status = SCP_E_SIZE;
+	}
+
+	VERBOSE("Sending response for SCP_READY command\n");
+
+	/*
+	 * Send our response back to SCP.
+	 * We are using the same SCPI header, just update the status field.
+	 */
+	scpi_cmd.status = status;
+	scpi_secure_message_start();
+	memcpy((void *) SCPI_SHARED_MEM_AP_TO_SCP, &scpi_cmd, sizeof(scpi_cmd));
+	scpi_secure_message_send(0);
+	scpi_secure_message_end();
+
+	return status == SCP_OK ? 0 : -1;
+}
+
+void scpi_set_css_power_state(unsigned int mpidr,
+		scpi_power_state_t cpu_state, scpi_power_state_t cluster_state,
+		scpi_power_state_t css_state)
+{
+	scpi_cmd_t *cmd;
+	uint32_t state = 0;
+	uint32_t *payload_addr;
+
+#if ARM_PLAT_MT
+	/*
+	 * The current SCPI driver only caters for single-threaded platforms.
+	 * Hence we ignore the thread ID (which is always 0) for such platforms.
+	 */
+	state |= (mpidr >> MPIDR_AFF1_SHIFT) & 0x0f;	/* CPU ID */
+	state |= ((mpidr >> MPIDR_AFF2_SHIFT) & 0x0f) << 4;	/* Cluster ID */
+#else
+	state |= mpidr & 0x0f;	/* CPU ID */
+	state |= (mpidr & 0xf00) >> 4;	/* Cluster ID */
+#endif /* ARM_PLAT_MT */
+
+	state |= cpu_state << 8;
+	state |= cluster_state << 12;
+	state |= css_state << 16;
+
+	scpi_secure_message_start();
+
+	/* Populate the command header */
+	cmd = SCPI_CMD_HEADER_AP_TO_SCP;
+	cmd->id = SCPI_CMD_SET_CSS_POWER_STATE;
+	cmd->set = SCPI_SET_NORMAL;
+	cmd->sender = 0;
+	cmd->size = sizeof(state);
+	/* Populate the command payload */
+	payload_addr = SCPI_CMD_PAYLOAD_AP_TO_SCP;
+	*payload_addr = state;
+	scpi_secure_message_send(sizeof(state));
+	/*
+	 * SCP does not reply to this command in order to avoid MHU interrupts
+	 * from the sender, which could interfere with its power state request.
+	 */
+
+	scpi_secure_message_end();
+}
+
+/*
+ * Query and obtain CSS power state from SCP.
+ *
+ * In response to the query, SCP returns power states of all CPUs in all
+ * clusters of the system. The returned response is then filtered based on the
+ * supplied MPIDR. Power states of requested cluster and CPUs within are updated
+ * via. supplied non-NULL pointer arguments.
+ *
+ * Returns 0 on success, or -1 on errors.
+ */
+int scpi_get_css_power_state(unsigned int mpidr, unsigned int *cpu_state_p,
+		unsigned int *cluster_state_p)
+{
+	scpi_cmd_t *cmd;
+	scpi_cmd_t response;
+	int power_state, cpu, cluster, rc = -1;
+
+	/*
+	 * Extract CPU and cluster membership of the given MPIDR. SCPI caters
+	 * for only up to 0xf clusters, and 8 CPUs per cluster
+	 */
+#if ARM_PLAT_MT
+	/*
+	 * The current SCPI driver only caters for single-threaded platforms.
+	 * Hence we ignore the thread ID (which is always 0) for such platforms.
+	 */
+	cpu = (mpidr >> MPIDR_AFF1_SHIFT) & MPIDR_AFFLVL_MASK;
+	cluster = (mpidr >> MPIDR_AFF2_SHIFT) & MPIDR_AFFLVL_MASK;
+#else
+	cpu = mpidr & MPIDR_AFFLVL_MASK;
+	cluster = (mpidr >> MPIDR_AFF1_SHIFT) & MPIDR_AFFLVL_MASK;
+#endif  /* ARM_PLAT_MT */
+	if (cpu >= 8 || cluster >= 0xf)
+		return -1;
+
+	scpi_secure_message_start();
+
+	/* Populate request headers */
+	zeromem(SCPI_CMD_HEADER_AP_TO_SCP, sizeof(*cmd));
+	cmd = SCPI_CMD_HEADER_AP_TO_SCP;
+	cmd->id = SCPI_CMD_GET_CSS_POWER_STATE;
+
+	/*
+	 * Send message and wait for SCP's response
+	 */
+	scpi_secure_message_send(0);
+	scpi_secure_message_receive(&response);
+
+	if (response.status != SCP_OK)
+		goto exit;
+
+	/* Validate SCP response */
+	if (!CHECK_RESPONSE(response, cluster))
+		goto exit;
+
+	/* Extract power states for required cluster */
+	power_state = *(((uint16_t *) SCPI_RES_PAYLOAD_SCP_TO_AP) + cluster);
+	if (CLUSTER_ID(power_state) != cluster)
+		goto exit;
+
+	/* Update power state via. pointers */
+	if (cluster_state_p)
+		*cluster_state_p = CLUSTER_POWER_STATE(power_state);
+	if (cpu_state_p)
+		*cpu_state_p = CPU_POWER_STATE(power_state);
+	rc = 0;
+
+exit:
+	scpi_secure_message_end();
+	return rc;
+}
+
+uint32_t scpi_sys_power_state(scpi_system_state_t system_state)
+{
+	scpi_cmd_t *cmd;
+	uint8_t *payload_addr;
+	scpi_cmd_t response;
+
+	scpi_secure_message_start();
+
+	/* Populate the command header */
+	cmd = SCPI_CMD_HEADER_AP_TO_SCP;
+	cmd->id = SCPI_CMD_SYS_POWER_STATE;
+	cmd->set = 0;
+	cmd->sender = 0;
+	cmd->size = sizeof(*payload_addr);
+	/* Populate the command payload */
+	payload_addr = SCPI_CMD_PAYLOAD_AP_TO_SCP;
+	*payload_addr = system_state & 0xff;
+	scpi_secure_message_send(sizeof(*payload_addr));
+
+	scpi_secure_message_receive(&response);
+
+	scpi_secure_message_end();
+
+	return response.status;
+}