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// SPDX-License-Identifier: GPL-2.0
/*
* Mailbox interface for Wilco Embedded Controller
*
* Copyright 2018 Google LLC
*
* The Wilco EC is similar to a typical ChromeOS embedded controller.
* It uses the same MEC based low-level communication and a similar
* protocol, but with some important differences. The EC firmware does
* not support the same mailbox commands so it is not registered as a
* cros_ec device type.
*
* Most messages follow a standard format, but there are some exceptions
* and an interface is provided to do direct/raw transactions that do not
* make assumptions about byte placement.
*/
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/io.h>
#include <linux/platform_data/wilco-ec.h>
#include <linux/platform_device.h>
#include "../cros_ec_lpc_mec.h"
/* Version of mailbox interface */
#define EC_MAILBOX_VERSION 0
/* Command to start mailbox transaction */
#define EC_MAILBOX_START_COMMAND 0xda
/* Version of EC protocol */
#define EC_MAILBOX_PROTO_VERSION 3
/* Number of header bytes to be counted as data bytes */
#define EC_MAILBOX_DATA_EXTRA 2
/* Maximum timeout */
#define EC_MAILBOX_TIMEOUT HZ
/* EC response flags */
#define EC_CMDR_DATA BIT(0) /* Data ready for host to read */
#define EC_CMDR_PENDING BIT(1) /* Write pending to EC */
#define EC_CMDR_BUSY BIT(2) /* EC is busy processing a command */
#define EC_CMDR_CMD BIT(3) /* Last host write was a command */
/**
* wilco_ec_response_timed_out() - Wait for EC response.
* @ec: EC device.
*
* Return: true if EC timed out, false if EC did not time out.
*/
static bool wilco_ec_response_timed_out(struct wilco_ec_device *ec)
{
unsigned long timeout = jiffies + EC_MAILBOX_TIMEOUT;
do {
if (!(inb(ec->io_command->start) &
(EC_CMDR_PENDING | EC_CMDR_BUSY)))
return false;
usleep_range(100, 200);
} while (time_before(jiffies, timeout));
return true;
}
/**
* wilco_ec_checksum() - Compute 8-bit checksum over data range.
* @data: Data to checksum.
* @size: Number of bytes to checksum.
*
* Return: 8-bit checksum of provided data.
*/
static u8 wilco_ec_checksum(const void *data, size_t size)
{
u8 *data_bytes = (u8 *)data;
u8 checksum = 0;
size_t i;
for (i = 0; i < size; i++)
checksum += data_bytes[i];
return checksum;
}
/**
* wilco_ec_prepare() - Prepare the request structure for the EC.
* @msg: EC message with request information.
* @rq: EC request structure to fill.
*/
static void wilco_ec_prepare(struct wilco_ec_message *msg,
struct wilco_ec_request *rq)
{
memset(rq, 0, sizeof(*rq));
rq->struct_version = EC_MAILBOX_PROTO_VERSION;
rq->mailbox_id = msg->type;
rq->mailbox_version = EC_MAILBOX_VERSION;
rq->data_size = msg->request_size;
/* Checksum header and data */
rq->checksum = wilco_ec_checksum(rq, sizeof(*rq));
rq->checksum += wilco_ec_checksum(msg->request_data, msg->request_size);
rq->checksum = -rq->checksum;
}
/**
* wilco_ec_transfer() - Perform actual data transfer.
* @ec: EC device.
* @msg: EC message data for request and response.
* @rq: Filled in request structure
*
* Context: ec->mailbox_lock should be held while using this function.
* Return: number of bytes received or negative error code on failure.
*/
static int wilco_ec_transfer(struct wilco_ec_device *ec,
struct wilco_ec_message *msg,
struct wilco_ec_request *rq)
{
struct wilco_ec_response *rs;
u8 checksum;
u8 flag;
/* Write request header, then data */
cros_ec_lpc_io_bytes_mec(MEC_IO_WRITE, 0, sizeof(*rq), (u8 *)rq);
cros_ec_lpc_io_bytes_mec(MEC_IO_WRITE, sizeof(*rq), msg->request_size,
msg->request_data);
/* Start the command */
outb(EC_MAILBOX_START_COMMAND, ec->io_command->start);
/* For some commands (eg shutdown) the EC will not respond, that's OK */
if (msg->flags & WILCO_EC_FLAG_NO_RESPONSE) {
dev_dbg(ec->dev, "EC does not respond to this command\n");
return 0;
}
/* Wait for it to complete */
if (wilco_ec_response_timed_out(ec)) {
dev_dbg(ec->dev, "response timed out\n");
return -ETIMEDOUT;
}
/* Check result */
flag = inb(ec->io_data->start);
if (flag) {
dev_dbg(ec->dev, "bad response: 0x%02x\n", flag);
return -EIO;
}
/* Read back response */
rs = ec->data_buffer;
checksum = cros_ec_lpc_io_bytes_mec(MEC_IO_READ, 0,
sizeof(*rs) + EC_MAILBOX_DATA_SIZE,
(u8 *)rs);
if (checksum) {
dev_dbg(ec->dev, "bad packet checksum 0x%02x\n", rs->checksum);
return -EBADMSG;
}
if (rs->result) {
dev_dbg(ec->dev, "EC reported failure: 0x%02x\n", rs->result);
return -EBADMSG;
}
if (rs->data_size != EC_MAILBOX_DATA_SIZE) {
dev_dbg(ec->dev, "unexpected packet size (%u != %u)\n",
rs->data_size, EC_MAILBOX_DATA_SIZE);
return -EMSGSIZE;
}
if (rs->data_size < msg->response_size) {
dev_dbg(ec->dev, "EC didn't return enough data (%u < %zu)\n",
rs->data_size, msg->response_size);
return -EMSGSIZE;
}
memcpy(msg->response_data, rs->data, msg->response_size);
return rs->data_size;
}
/**
* wilco_ec_mailbox() - Send EC request and receive EC response.
* @ec: EC device.
* @msg: EC message data for request and response.
*
* On entry msg->type, msg->request_size, and msg->request_data should all be
* filled in. If desired, msg->flags can be set.
*
* If a response is expected, msg->response_size should be set, and
* msg->response_data should point to a buffer with enough space. On exit
* msg->response_data will be filled.
*
* Return: number of bytes received or negative error code on failure.
*/
int wilco_ec_mailbox(struct wilco_ec_device *ec, struct wilco_ec_message *msg)
{
struct wilco_ec_request *rq;
int ret;
dev_dbg(ec->dev, "type=%04x flags=%02x rslen=%zu rqlen=%zu\n",
msg->type, msg->flags, msg->response_size, msg->request_size);
mutex_lock(&ec->mailbox_lock);
/* Prepare request packet */
rq = ec->data_buffer;
wilco_ec_prepare(msg, rq);
ret = wilco_ec_transfer(ec, msg, rq);
mutex_unlock(&ec->mailbox_lock);
return ret;
}
EXPORT_SYMBOL_GPL(wilco_ec_mailbox);
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