1 // SPDX-License-Identifier: GPL-2.0+
2 // Expose an I2C passthrough to the ChromeOS EC.
4 // Copyright (C) 2013 Google, Inc.
6 #include <linux/module.h>
8 #include <linux/mfd/cros_ec.h>
9 #include <linux/mfd/cros_ec_commands.h>
10 #include <linux/platform_device.h>
11 #include <linux/slab.h>
13 #define I2C_MAX_RETRIES 3
16 * struct ec_i2c_device - Driver data for I2C tunnel
20 * @ec: Pointer to EC device
21 * @remote_bus: The EC bus number we tunnel to on the other side.
22 * @request_buf: Buffer for transmitting data; we expect most transfers to fit.
23 * @response_buf: Buffer for receiving data; we expect most transfers to fit.
26 struct ec_i2c_device {
28 struct i2c_adapter adap;
29 struct cros_ec_device *ec;
38 * ec_i2c_count_message - Count bytes needed for ec_i2c_construct_message
40 * @i2c_msgs: The i2c messages to read
41 * @num: The number of i2c messages.
43 * Returns the number of bytes the messages will take up.
45 static int ec_i2c_count_message(const struct i2c_msg i2c_msgs[], int num)
50 size = sizeof(struct ec_params_i2c_passthru);
51 size += num * sizeof(struct ec_params_i2c_passthru_msg);
52 for (i = 0; i < num; i++)
53 if (!(i2c_msgs[i].flags & I2C_M_RD))
54 size += i2c_msgs[i].len;
60 * ec_i2c_construct_message - construct a message to go to the EC
62 * This function effectively stuffs the standard i2c_msg format of Linux into
63 * a format that the EC understands.
65 * @buf: The buffer to fill. We assume that the buffer is big enough.
66 * @i2c_msgs: The i2c messages to read.
67 * @num: The number of i2c messages.
68 * @bus_num: The remote bus number we want to talk to.
70 * Returns 0 or a negative error number.
72 static int ec_i2c_construct_message(u8 *buf, const struct i2c_msg i2c_msgs[],
75 struct ec_params_i2c_passthru *params;
79 out_data = buf + sizeof(struct ec_params_i2c_passthru) +
80 num * sizeof(struct ec_params_i2c_passthru_msg);
82 params = (struct ec_params_i2c_passthru *)buf;
83 params->port = bus_num;
84 params->num_msgs = num;
85 for (i = 0; i < num; i++) {
86 const struct i2c_msg *i2c_msg = &i2c_msgs[i];
87 struct ec_params_i2c_passthru_msg *msg = ¶ms->msg[i];
89 msg->len = i2c_msg->len;
90 msg->addr_flags = i2c_msg->addr;
92 if (i2c_msg->flags & I2C_M_TEN)
95 if (i2c_msg->flags & I2C_M_RD) {
96 msg->addr_flags |= EC_I2C_FLAG_READ;
98 memcpy(out_data, i2c_msg->buf, msg->len);
107 * ec_i2c_count_response - Count bytes needed for ec_i2c_parse_response
109 * @i2c_msgs: The i2c messages to to fill up.
110 * @num: The number of i2c messages expected.
112 * Returns the number of response bytes expeced.
114 static int ec_i2c_count_response(struct i2c_msg i2c_msgs[], int num)
119 size = sizeof(struct ec_response_i2c_passthru);
120 for (i = 0; i < num; i++)
121 if (i2c_msgs[i].flags & I2C_M_RD)
122 size += i2c_msgs[i].len;
128 * ec_i2c_parse_response - Parse a response from the EC
130 * We'll take the EC's response and copy it back into msgs.
132 * @buf: The buffer to parse.
133 * @i2c_msgs: The i2c messages to to fill up.
134 * @num: The number of i2c messages; will be modified to include the actual
137 * Returns 0 or a negative error number.
139 static int ec_i2c_parse_response(const u8 *buf, struct i2c_msg i2c_msgs[],
142 const struct ec_response_i2c_passthru *resp;
146 in_data = buf + sizeof(struct ec_response_i2c_passthru);
148 resp = (const struct ec_response_i2c_passthru *)buf;
149 if (resp->i2c_status & EC_I2C_STATUS_TIMEOUT)
151 else if (resp->i2c_status & EC_I2C_STATUS_NAK)
153 else if (resp->i2c_status & EC_I2C_STATUS_ERROR)
156 /* Other side could send us back fewer messages, but not more */
157 if (resp->num_msgs > *num)
159 *num = resp->num_msgs;
161 for (i = 0; i < *num; i++) {
162 struct i2c_msg *i2c_msg = &i2c_msgs[i];
164 if (i2c_msgs[i].flags & I2C_M_RD) {
165 memcpy(i2c_msg->buf, in_data, i2c_msg->len);
166 in_data += i2c_msg->len;
173 static int ec_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg i2c_msgs[],
176 struct ec_i2c_device *bus = adap->algo_data;
177 struct device *dev = bus->dev;
178 const u16 bus_num = bus->remote_bus;
183 struct cros_ec_command *msg;
185 request_len = ec_i2c_count_message(i2c_msgs, num);
186 if (request_len < 0) {
187 dev_warn(dev, "Error constructing message %d\n", request_len);
191 response_len = ec_i2c_count_response(i2c_msgs, num);
192 if (response_len < 0) {
193 /* Unexpected; no errors should come when NULL response */
194 dev_warn(dev, "Error preparing response %d\n", response_len);
198 alloc_size = max(request_len, response_len);
199 msg = kmalloc(sizeof(*msg) + alloc_size, GFP_KERNEL);
203 result = ec_i2c_construct_message(msg->data, i2c_msgs, num, bus_num);
205 dev_err(dev, "Error constructing EC i2c message %d\n", result);
210 msg->command = EC_CMD_I2C_PASSTHRU;
211 msg->outsize = request_len;
212 msg->insize = response_len;
214 result = cros_ec_cmd_xfer_status(bus->ec, msg);
216 dev_err(dev, "Error transferring EC i2c message %d\n", result);
220 result = ec_i2c_parse_response(msg->data, i2c_msgs, &num);
224 /* Indicate success by saying how many messages were sent */
231 static u32 ec_i2c_functionality(struct i2c_adapter *adap)
233 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
236 static const struct i2c_algorithm ec_i2c_algorithm = {
237 .master_xfer = ec_i2c_xfer,
238 .functionality = ec_i2c_functionality,
241 static int ec_i2c_probe(struct platform_device *pdev)
243 struct device_node *np = pdev->dev.of_node;
244 struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
245 struct device *dev = &pdev->dev;
246 struct ec_i2c_device *bus = NULL;
251 dev_err(dev, "Missing sendrecv\n");
255 bus = devm_kzalloc(dev, sizeof(*bus), GFP_KERNEL);
259 err = of_property_read_u32(np, "google,remote-bus", &remote_bus);
261 dev_err(dev, "Couldn't read remote-bus property\n");
264 bus->remote_bus = remote_bus;
269 bus->adap.owner = THIS_MODULE;
270 strlcpy(bus->adap.name, "cros-ec-i2c-tunnel", sizeof(bus->adap.name));
271 bus->adap.algo = &ec_i2c_algorithm;
272 bus->adap.algo_data = bus;
273 bus->adap.dev.parent = &pdev->dev;
274 bus->adap.dev.of_node = np;
275 bus->adap.retries = I2C_MAX_RETRIES;
277 err = i2c_add_adapter(&bus->adap);
280 platform_set_drvdata(pdev, bus);
285 static int ec_i2c_remove(struct platform_device *dev)
287 struct ec_i2c_device *bus = platform_get_drvdata(dev);
289 i2c_del_adapter(&bus->adap);
295 static const struct of_device_id cros_ec_i2c_of_match[] = {
296 { .compatible = "google,cros-ec-i2c-tunnel" },
299 MODULE_DEVICE_TABLE(of, cros_ec_i2c_of_match);
302 static struct platform_driver ec_i2c_tunnel_driver = {
303 .probe = ec_i2c_probe,
304 .remove = ec_i2c_remove,
306 .name = "cros-ec-i2c-tunnel",
307 .of_match_table = of_match_ptr(cros_ec_i2c_of_match),
311 module_platform_driver(ec_i2c_tunnel_driver);
313 MODULE_LICENSE("GPL");
314 MODULE_DESCRIPTION("EC I2C tunnel driver");
315 MODULE_ALIAS("platform:cros-ec-i2c-tunnel");