// SPDX-License-Identifier: GPL-2.0+
// Expose an I2C passthrough to the ChromeOS EC.
//
// Copyright (C) 2013 Google, Inc.
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/mfd/cros_ec.h>
#include <linux/mfd/cros_ec_commands.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#define I2C_MAX_RETRIES 3
/**
* struct ec_i2c_device - Driver data for I2C tunnel
*
* @dev: Device node
* @adap: I2C adapter
* @ec: Pointer to EC device
* @remote_bus: The EC bus number we tunnel to on the other side.
* @request_buf: Buffer for transmitting data; we expect most transfers to fit.
* @response_buf: Buffer for receiving data; we expect most transfers to fit.
*/
struct ec_i2c_device {
struct device *dev;
struct i2c_adapter adap;
struct cros_ec_device *ec;
u16 remote_bus;
u8 request_buf[256];
u8 response_buf[256];
};
/**
* ec_i2c_count_message - Count bytes needed for ec_i2c_construct_message
*
* @i2c_msgs: The i2c messages to read
* @num: The number of i2c messages.
*
* Returns the number of bytes the messages will take up.
*/
static int ec_i2c_count_message(const struct i2c_msg i2c_msgs[], int num)
{
int i;
int size;
size = sizeof(struct ec_params_i2c_passthru);
size += num * sizeof(struct ec_params_i2c_passthru_msg);
for (i = 0; i < num; i++)
if (!(i2c_msgs[i].flags & I2C_M_RD))
size += i2c_msgs[i].len;
return size;
}
/**
* ec_i2c_construct_message - construct a message to go to the EC
*
* This function effectively stuffs the standard i2c_msg format of Linux into
* a format that the EC understands.
*
* @buf: The buffer to fill. We assume that the buffer is big enough.
* @i2c_msgs: The i2c messages to read.
* @num: The number of i2c messages.
* @bus_num: The remote bus number we want to talk to.
*
* Returns 0 or a negative error number.
*/
static int ec_i2c_construct_message(u8 *buf, const struct i2c_msg i2c_msgs[],
int num, u16 bus_num)
{
struct ec_params_i2c_passthru *params;
u8 *out_data;
int i;
out_data = buf + sizeof(struct ec_params_i2c_passthru) +
num * sizeof(struct ec_params_i2c_passthru_msg);
params = (struct ec_params_i2c_passthru *)buf;
params->port = bus_num;
params->num_msgs = num;
for (i = 0; i < num; i++) {
const struct i2c_msg *i2c_msg = &i2c_msgs[i];
struct ec_params_i2c_passthru_msg *msg = ¶ms->msg[i];
msg->len = i2c_msg->len;
msg->addr_flags = i2c_msg->addr;
if (i2c_msg->flags & I2C_M_TEN)
return -EINVAL;
if (i2c_msg->flags & I2C_M_RD) {
msg->addr_flags |= EC_I2C_FLAG_READ;
} else {
memcpy(out_data, i2c_msg->buf, msg->len);
out_data += msg->len;
}
}
return 0;
}
/**
* ec_i2c_count_response - Count bytes needed for ec_i2c_parse_response
*
* @i2c_msgs: The i2c messages to to fill up.
* @num: The number of i2c messages expected.
*
* Returns the number of response bytes expeced.
*/
static int ec_i2c_count_response(struct i2c_msg i2c_msgs[], int num)
{
int size;
int i;
size = sizeof(struct ec_response_i2c_passthru);
for (i = 0; i < num; i++)
if (i2c_msgs[i].flags & I2C_M_RD)
size += i2c_msgs[i].len;
return size;
}
/**
* ec_i2c_parse_response - Parse a response from the EC
*
* We'll take the EC's response and copy it back into msgs.
*
* @buf: The buffer to parse.
* @i2c_msgs: The i2c messages to to fill up.
* @num: The number of i2c messages; will be modified to include the actual
* number received.
*
* Returns 0 or a negative error number.
*/
static int ec_i2c_parse_response(const u8 *buf, struct i2c_msg i2c_msgs[],
int *num)
{
const struct ec_response_i2c_passthru *resp;
const u8 *in_data;
int i;
in_data = buf + sizeof(struct ec_response_i2c_passthru);
resp = (const struct ec_response_i2c_passthru *)buf;
if (resp->i2c_status & EC_I2C_STATUS_TIMEOUT)
return -ETIMEDOUT;
else if (resp->i2c_status & EC_I2C_STATUS_NAK)
return -ENXIO;
else if (resp->i2c_status & EC_I2C_STATUS_ERROR)
return -EIO;
/* Other side could send us back fewer messages, but not more */
if (resp->num_msgs > *num)
return -EPROTO;
*num = resp->num_msgs;
for (i = 0; i < *num; i++) {
struct i2c_msg *i2c_msg = &i2c_msgs[i];
if (i2c_msgs[i].flags & I2C_M_RD) {
memcpy(i2c_msg->buf, in_data, i2c_msg->len);
in_data += i2c_msg->len;
}
}
return 0;
}
static int ec_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg i2c_msgs[],
int num)
{
struct ec_i2c_device *bus = adap->algo_data;
struct device *dev = bus->dev;
const u16 bus_num = bus->remote_bus;
int request_len;
int response_len;
int alloc_size;
int result;
struct cros_ec_command *msg;
request_len = ec_i2c_count_message(i2c_msgs, num);
if (request_len < 0) {
dev_warn(dev, "Error constructing message %d\n", request_len);
return request_len;
}
response_len = ec_i2c_count_response(i2c_msgs, num);
if (response_len < 0) {
/* Unexpected; no errors should come when NULL response */
dev_warn(dev, "Error preparing response %d\n", response_len);
return response_len;
}
alloc_size = max(request_len, response_len);
msg = kmalloc(sizeof(*msg) + alloc_size, GFP_KERNEL);
if (!msg)
return -ENOMEM;
result = ec_i2c_construct_message(msg->data, i2c_msgs, num, bus_num);
if (result) {
dev_err(dev, "Error constructing EC i2c message %d\n", result);
goto exit;
}
msg->version = 0;
msg->command = EC_CMD_I2C_PASSTHRU;
msg->outsize = request_len;
msg->insize = response_len;
result = cros_ec_cmd_xfer_status(bus->ec, msg);
if (result < 0) {
dev_err(dev, "Error transferring EC i2c message %d\n", result);
goto exit;
}
result = ec_i2c_parse_response(msg->data, i2c_msgs, &num);
if (result < 0)
goto exit;
/* Indicate success by saying how many messages were sent */
result = num;
exit:
kfree(msg);
return result;
}
static u32 ec_i2c_functionality(struct i2c_adapter *adap)
{
return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}
static const struct i2c_algorithm ec_i2c_algorithm = {
.master_xfer = ec_i2c_xfer,
.functionality = ec_i2c_functionality,
};
static int ec_i2c_probe(struct platform_device *pdev)
{
struct device_node *np = pdev->dev.of_node;
struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
struct device *dev = &pdev->dev;
struct ec_i2c_device *bus = NULL;
u32 remote_bus;
int err;
if (!ec->cmd_xfer) {
dev_err(dev, "Missing sendrecv\n");
return -EINVAL;
}
bus = devm_kzalloc(dev, sizeof(*bus), GFP_KERNEL);
if (bus == NULL)
return -ENOMEM;
err = of_property_read_u32(np, "google,remote-bus", &remote_bus);
if (err) {
dev_err(dev, "Couldn't read remote-bus property\n");
return err;
}
bus->remote_bus = remote_bus;
bus->ec = ec;
bus->dev = dev;
bus->adap.owner = THIS_MODULE;
strlcpy(bus->adap.name, "cros-ec-i2c-tunnel", sizeof(bus->adap.name));
bus->adap.algo = &ec_i2c_algorithm;
bus->adap.algo_data = bus;
bus->adap.dev.parent = &pdev->dev;
bus->adap.dev.of_node = np;
bus->adap.retries = I2C_MAX_RETRIES;
err = i2c_add_adapter(&bus->adap);
if (err)
return err;
platform_set_drvdata(pdev, bus);
return err;
}
static int ec_i2c_remove(struct platform_device *dev)
{
struct ec_i2c_device *bus = platform_get_drvdata(dev);
i2c_del_adapter(&bus->adap);
return 0;
}
#ifdef CONFIG_OF
static const struct of_device_id cros_ec_i2c_of_match[] = {
{ .compatible = "google,cros-ec-i2c-tunnel" },
{},
};
MODULE_DEVICE_TABLE(of, cros_ec_i2c_of_match);
#endif
static struct platform_driver ec_i2c_tunnel_driver = {
.probe = ec_i2c_probe,
.remove = ec_i2c_remove,
.driver = {
.name = "cros-ec-i2c-tunnel",
.of_match_table = of_match_ptr(cros_ec_i2c_of_match),
},
};
module_platform_driver(ec_i2c_tunnel_driver);
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("EC I2C tunnel driver");
MODULE_ALIAS("platform:cros-ec-i2c-tunnel");
