src/ec/google/chromeec/ec_i2c.c

/*
 * This file is part of the coreboot project.
 *
 * Copyright (C) 2013 Google Inc.  All rights reserved.
 *
 * 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; version 2 of the License
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <arch/io.h>
#include <console/console.h>
#include <delay.h>
#include <device/i2c.h>
#include <stdint.h>
#include <string.h>
#include "ec.h"
#include "ec_commands.h"

/* Command (host->device) format for I2C:
 *  uint8_t version, cmd, len, data[len], checksum;
 *
 * Response (device->host) format for I2C:
 *  uint8_t response, len, data[len], checksum;
 *
 * Note the location of checksum is different from LPC protocol.
 *
 * The length is 8 bit so maximum data size is 0xff.
 * Any I2C command should fit in 0xff + 4 bytes, and max response length
 * is 0xff + 3 bytes.
 */
#define MAX_I2C_DATA_SIZE		(0xff)

typedef struct {
	uint8_t version;
	uint8_t command;
	uint8_t length;
	uint8_t data[MAX_I2C_DATA_SIZE + 1];
} EcCommandI2c;

typedef struct {
	uint8_t response;
	uint8_t length;
	uint8_t data[MAX_I2C_DATA_SIZE + 1];
} EcResponseI2c;

static inline void i2c_dump(int bus, int chip, const uint8_t *data, size_t size)
{
#ifdef TRACE_CHROMEEC
	printk(BIOS_INFO, "i2c: bus=%d, chip=%#x, size=%d, data: ", bus, chip,
	       size);
	while (size-- > 0) {
		printk(BIOS_INFO, "%02X ", *data++);
	}
	printk(BIOS_INFO, "\n");
#endif
}

static int ec_verify_checksum(const EcResponseI2c *resp)
{
	size_t size = sizeof(*resp) - sizeof(resp->data) + resp->length;
	uint8_t calculated = google_chromeec_calc_checksum(
			(const uint8_t *)resp, size);
	uint8_t received = resp->data[resp->length];
	if (calculated != received) {
		printk(BIOS_ERR, "%s: Unmatch (rx: %#02x, calc: %#02x)\n",
		       __func__, received, calculated);
		return 0;
	}
	return 1;
}

static void ec_fill_checksum(EcCommandI2c *cmd)
{
	size_t size = sizeof(*cmd) - sizeof(cmd->data) + cmd->length;
	cmd->data[cmd->length] = google_chromeec_calc_checksum(
			(const uint8_t *)cmd, size);
}

int google_chromeec_command(struct chromeec_command *cec_command)
{
	EcCommandI2c cmd;
	EcResponseI2c resp;
	int bus = CONFIG_EC_GOOGLE_CHROMEEC_I2C_BUS;
	int chip = CONFIG_EC_GOOGLE_CHROMEEC_I2C_CHIP;
	size_t size_i2c_cmd = (sizeof(cmd) - sizeof(cmd.data) +
			       cec_command->cmd_size_in + 1),
	       size_i2c_resp = (sizeof(resp) - sizeof(resp.data) +
				cec_command->cmd_size_out + 1);

	if (cec_command->cmd_size_in > MAX_I2C_DATA_SIZE ||
	    cec_command->cmd_size_out > MAX_I2C_DATA_SIZE) {
		printk(BIOS_ERR, "%s: Command data size too large (%d,%d)\n",
		       __func__, cec_command->cmd_size_in,
		       cec_command->cmd_size_out);
		cec_command->cmd_code = EC_RES_INVALID_PARAM;
		return 1;
	}

	/* Construct command. */
	cmd.version = EC_CMD_VERSION0 + cec_command->cmd_version;
	cmd.command = cec_command->cmd_code;
	cmd.length = cec_command->cmd_size_in;
	memcpy(cmd.data, cec_command->cmd_data_in, cmd.length);
	ec_fill_checksum(&cmd);

	/* Start I2C communication */
	i2c_dump(bus, chip, (const uint8_t *)&cmd, size_i2c_cmd);
	if (i2c_write(bus, chip, 0, 0, (uint8_t *)&cmd, size_i2c_cmd) != 0) {
		printk(BIOS_ERR, "%s: Cannot complete write to i2c-%d:%#x\n",
		       __func__, bus, chip);
		cec_command->cmd_code = EC_RES_ERROR;
		return 1;
	}
	if (i2c_read(bus, chip, 0, 0, (uint8_t *)&resp, size_i2c_resp) != 0) {
		printk(BIOS_ERR, "%s: Cannot complete read from i2c-%d:%#x\n",
		       __func__, bus, chip);
		cec_command->cmd_code = EC_RES_ERROR;
		return 1;
	}

	/* Verify and return response */
	cec_command->cmd_code = resp.response;
	if (resp.response != EC_RES_SUCCESS) {
		printk(BIOS_DEBUG, "%s: Received bad result code %d\n",
		       __func__, (int)resp.response);
		return 1;
	}
	if (resp.length > cec_command->cmd_size_out) {
		printk(BIOS_ERR, "%s: Received len %#02x too large\n",
		       __func__, (int)resp.length);
		cec_command->cmd_code = EC_RES_INVALID_RESPONSE;
		return 1;
	}
	if (!ec_verify_checksum(&resp)) {
		cec_command->cmd_code = EC_RES_INVALID_CHECKSUM;
		return 1;
	}
	cec_command->cmd_size_out = resp.length;
	memcpy(cec_command->cmd_data_out, resp.data, resp.length);
	return 0;
}

#ifndef __PRE_RAM__
u8 google_chromeec_get_event(void)
{
	printk(BIOS_ERR, "%s: Not supported.\n", __func__);
	return 0;
}
#endif