path: root/drivers/platform/chrome/cros_ec_proto.c

// SPDX-License-Identifier: GPL-2.0
// ChromeOS EC communication protocol helper functions
//
// Copyright (C) 2015 Google, Inc

#include <linux/delay.h>
#include <linux/device.h>
#include <linux/module.h>
#include <linux/platform_data/cros_ec_commands.h>
#include <linux/platform_data/cros_ec_proto.h>
#include <linux/slab.h>
#include <asm/unaligned.h>

#include "cros_ec_trace.h"

#define EC_COMMAND_RETRIES	50

static const int cros_ec_error_map[] = {
	[EC_RES_INVALID_COMMAND] = -EOPNOTSUPP,
	[EC_RES_ERROR] = -EIO,
	[EC_RES_INVALID_PARAM] = -EINVAL,
	[EC_RES_ACCESS_DENIED] = -EACCES,
	[EC_RES_INVALID_RESPONSE] = -EPROTO,
	[EC_RES_INVALID_VERSION] = -ENOPROTOOPT,
	[EC_RES_INVALID_CHECKSUM] = -EBADMSG,
	[EC_RES_IN_PROGRESS] = -EINPROGRESS,
	[EC_RES_UNAVAILABLE] = -ENODATA,
	[EC_RES_TIMEOUT] = -ETIMEDOUT,
	[EC_RES_OVERFLOW] = -EOVERFLOW,
	[EC_RES_INVALID_HEADER] = -EBADR,
	[EC_RES_REQUEST_TRUNCATED] = -EBADR,
	[EC_RES_RESPONSE_TOO_BIG] = -EFBIG,
	[EC_RES_BUS_ERROR] = -EFAULT,
	[EC_RES_BUSY] = -EBUSY,
	[EC_RES_INVALID_HEADER_VERSION] = -EBADMSG,
	[EC_RES_INVALID_HEADER_CRC] = -EBADMSG,
	[EC_RES_INVALID_DATA_CRC] = -EBADMSG,
	[EC_RES_DUP_UNAVAILABLE] = -ENODATA,
};

static int cros_ec_map_error(uint32_t result)
{
	int ret = 0;

	if (result != EC_RES_SUCCESS) {
		if (result < ARRAY_SIZE(cros_ec_error_map) && cros_ec_error_map[result])
			ret = cros_ec_error_map[result];
		else
			ret = -EPROTO;
	}

	return ret;
}

static int prepare_packet(struct cros_ec_device *ec_dev,
			  struct cros_ec_command *msg)
{
	struct ec_host_request *request;
	u8 *out;
	int i;
	u8 csum = 0;

	BUG_ON(msg->outsize + sizeof(*request) > ec_dev->dout_size);

	out = ec_dev->dout;
	request = (struct ec_host_request *)out;
	request->struct_version = EC_HOST_REQUEST_VERSION;
	request->checksum = 0;
	request->command = msg->command;
	request->command_version = msg->version;
	request->reserved = 0;
	request->data_len = msg->outsize;

	for (i = 0; i < sizeof(*request); i++)
		csum += out[i];

	/* Copy data and update checksum */
	memcpy(out + sizeof(*request), msg->data, msg->outsize);
	for (i = 0; i < msg->outsize; i++)
		csum += msg->data[i];

	request->checksum = -csum;

	return sizeof(*request) + msg->outsize;
}

static int send_command(struct cros_ec_device *ec_dev,
			struct cros_ec_command *msg)
{
	int ret;
	int (*xfer_fxn)(struct cros_ec_device *ec, struct cros_ec_command *msg);

	if (ec_dev->proto_version > 2)
		xfer_fxn = ec_dev->pkt_xfer;
	else
		xfer_fxn = ec_dev->cmd_xfer;

	if (!xfer_fxn) {
		/*
		 * This error can happen if a communication error happened and
		 * the EC is trying to use protocol v2, on an underlying
		 * communication mechanism that does not support v2.
		 */
		dev_err_once(ec_dev->dev,
			     "missing EC transfer API, cannot send command\n");
		return -EIO;
	}

	trace_cros_ec_request_start(msg);
	ret = (*xfer_fxn)(ec_dev, msg);
	trace_cros_ec_request_done(msg, ret);
	if (msg->result == EC_RES_IN_PROGRESS) {
		int i;
		struct cros_ec_command *status_msg;
		struct ec_response_get_comms_status *status;

		status_msg = kmalloc(sizeof(*status_msg) + sizeof(*status),
				     GFP_KERNEL);
		if (!status_msg)
			return -ENOMEM;

		status_msg->version = 0;
		status_msg->command = EC_CMD_GET_COMMS_STATUS;
		status_msg->insize = sizeof(*status);
		status_msg->outsize = 0;

		/*
		 * Query the EC's status until it's no longer busy or
		 * we encounter an error.
		 */
		for (i = 0; i < EC_COMMAND_RETRIES; i++) {
			usleep_range(10000, 11000);

			trace_cros_ec_request_start(status_msg);
			ret = (*xfer_fxn)(ec_dev, status_msg);
			trace_cros_ec_request_done(status_msg, ret);
			if (ret == -EAGAIN)
				continue;
			if (ret < 0)
				break;

			msg->result = status_msg->result;
			if (status_msg->result != EC_RES_SUCCESS)
				break;

			status = (struct ec_response_get_comms_status *)
				 status_msg->data;
			if (!(status->flags & EC_COMMS_STATUS_PROCESSING))
				break;
		}

		kfree(status_msg);
	}

	return ret;
}

/**
 * cros_ec_prepare_tx() - Prepare an outgoing message in the output buffer.
 * @ec_dev: Device to register.
 * @msg: Message to write.
 *
 * This is intended to be used by all ChromeOS EC drivers, but at present
 * only SPI uses it. Once LPC uses the same protocol it can start using it.
 * I2C could use it now, with a refactor of the existing code.
 *
 * Return: number of prepared bytes on success or negative error code.
 */
int cros_ec_prepare_tx(struct cros_ec_device *ec_dev,
		       struct cros_ec_command *msg)
{
	u8 *out;
	u8 csum;
	int i;

	if (ec_dev->proto_version > 2)
		return prepare_packet(ec_dev, msg);

	BUG_ON(msg->outsize > EC_PROTO2_MAX_PARAM_SIZE);
	out = ec_dev->dout;
	out[0] = EC_CMD_VERSION0 + msg->version;
	out[1] = msg->command