sq_scpi.c

/*
 * Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#include <arch_helpers.h>
#include <assert.h>
#include <platform_def.h>
#include <sq_common.h>
#include <debug.h>
#include <string.h>
#include "sq_mhu.h"
#include "sq_scpi.h"

#define SCPI_SHARED_MEM_SCP_TO_AP	PLAT_SQ_SCP_COM_SHARED_MEM_BASE
#define SCPI_SHARED_MEM_AP_TO_SCP	(PLAT_SQ_SCP_COM_SHARED_MEM_BASE \
								 + 0x100)

#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)))

/* 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;
	scpi_status_t status = SCP_OK;

	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 */
	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_sq_power_state(unsigned int mpidr, scpi_power_state_t cpu_state,
		scpi_power_state_t cluster_state, scpi_power_state_t sq_state)
{
	scpi_cmd_t *cmd;
	uint32_t state = 0;
	uint32_t *payload_addr;

	state |= mpidr & 0x0f;	/* CPU ID */
	state |= (mpidr & 0xf00) >> 4;	/* Cluster ID */
	state |= cpu_state << 8;
	state |= cluster_state << 12;
	state |= sq_state << 16;

	scpi_secure_message_start();

	/* Populate the command header */
	cmd = SCPI_CMD_HEADER_AP_TO_SCP;
	cmd->id = SCPI_CMD_SET_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();
}

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;
}