1 /* 2 * Copyright (C) 2013 Google, Inc 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License as published by 6 * the Free Software Foundation; either version 2 of the License, or 7 * (at your option) any later version. 8 * 9 * Expose an I2C passthrough to the ChromeOS EC. 10 */ 11 12 #include <linux/module.h> 13 #include <linux/i2c.h> 14 #include <linux/mfd/cros_ec.h> 15 #include <linux/mfd/cros_ec_commands.h> 16 #include <linux/platform_device.h> 17 #include <linux/slab.h> 18 19 #define I2C_MAX_RETRIES 3 20 21 /** 22 * struct ec_i2c_device - Driver data for I2C tunnel 23 * 24 * @dev: Device node 25 * @adap: I2C adapter 26 * @ec: Pointer to EC device 27 * @remote_bus: The EC bus number we tunnel to on the other side. 28 * @request_buf: Buffer for transmitting data; we expect most transfers to fit. 29 * @response_buf: Buffer for receiving data; we expect most transfers to fit. 30 */ 31 32 struct ec_i2c_device { 33 struct device *dev; 34 struct i2c_adapter adap; 35 struct cros_ec_device *ec; 36 37 u16 remote_bus; 38 39 u8 request_buf[256]; 40 u8 response_buf[256]; 41 }; 42 43 /** 44 * ec_i2c_count_message - Count bytes needed for ec_i2c_construct_message 45 * 46 * @i2c_msgs: The i2c messages to read 47 * @num: The number of i2c messages. 48 * 49 * Returns the number of bytes the messages will take up. 50 */ 51 static int ec_i2c_count_message(const struct i2c_msg i2c_msgs[], int num) 52 { 53 int i; 54 int size; 55 56 size = sizeof(struct ec_params_i2c_passthru); 57 size += num * sizeof(struct ec_params_i2c_passthru_msg); 58 for (i = 0; i < num; i++) 59 if (!(i2c_msgs[i].flags & I2C_M_RD)) 60 size += i2c_msgs[i].len; 61 62 return size; 63 } 64 65 /** 66 * ec_i2c_construct_message - construct a message to go to the EC 67 * 68 * This function effectively stuffs the standard i2c_msg format of Linux into 69 * a format that the EC understands. 70 * 71 * @buf: The buffer to fill. We assume that the buffer is big enough. 72 * @i2c_msgs: The i2c messages to read. 73 * @num: The number of i2c messages. 74 * @bus_num: The remote bus number we want to talk to. 75 * 76 * Returns 0 or a negative error number. 77 */ 78 static int ec_i2c_construct_message(u8 *buf, const struct i2c_msg i2c_msgs[], 79 int num, u16 bus_num) 80 { 81 struct ec_params_i2c_passthru *params; 82 u8 *out_data; 83 int i; 84 85 out_data = buf + sizeof(struct ec_params_i2c_passthru) + 86 num * sizeof(struct ec_params_i2c_passthru_msg); 87 88 params = (struct ec_params_i2c_passthru *)buf; 89 params->port = bus_num; 90 params->num_msgs = num; 91 for (i = 0; i < num; i++) { 92 const struct i2c_msg *i2c_msg = &i2c_msgs[i]; 93 struct ec_params_i2c_passthru_msg *msg = ¶ms->msg[i]; 94 95 msg->len = i2c_msg->len; 96 msg->addr_flags = i2c_msg->addr; 97 98 if (i2c_msg->flags & I2C_M_TEN) 99 return -EINVAL; 100 101 if (i2c_msg->flags & I2C_M_RD) { 102 msg->addr_flags |= EC_I2C_FLAG_READ; 103 } else { 104 memcpy(out_data, i2c_msg->buf, msg->len); 105 out_data += msg->len; 106 } 107 } 108 109 return 0; 110 } 111 112 /** 113 * ec_i2c_count_response - Count bytes needed for ec_i2c_parse_response 114 * 115 * @i2c_msgs: The i2c messages to to fill up. 116 * @num: The number of i2c messages expected. 117 * 118 * Returns the number of response bytes expeced. 119 */ 120 static int ec_i2c_count_response(struct i2c_msg i2c_msgs[], int num) 121 { 122 int size; 123 int i; 124 125 size = sizeof(struct ec_response_i2c_passthru); 126 for (i = 0; i < num; i++) 127 if (i2c_msgs[i].flags & I2C_M_RD) 128 size += i2c_msgs[i].len; 129 130 return size; 131 } 132 133 /** 134 * ec_i2c_parse_response - Parse a response from the EC 135 * 136 * We'll take the EC's response and copy it back into msgs. 137 * 138 * @buf: The buffer to parse. 139 * @i2c_msgs: The i2c messages to to fill up. 140 * @num: The number of i2c messages; will be modified to include the actual 141 * number received. 142 * 143 * Returns 0 or a negative error number. 144 */ 145 static int ec_i2c_parse_response(const u8 *buf, struct i2c_msg i2c_msgs[], 146 int *num) 147 { 148 const struct ec_response_i2c_passthru *resp; 149 const u8 *in_data; 150 int i; 151 152 in_data = buf + sizeof(struct ec_response_i2c_passthru); 153 154 resp = (const struct ec_response_i2c_passthru *)buf; 155 if (resp->i2c_status & EC_I2C_STATUS_TIMEOUT) 156 return -ETIMEDOUT; 157 else if (resp->i2c_status & EC_I2C_STATUS_ERROR) 158 return -EREMOTEIO; 159 160 /* Other side could send us back fewer messages, but not more */ 161 if (resp->num_msgs > *num) 162 return -EPROTO; 163 *num = resp->num_msgs; 164 165 for (i = 0; i < *num; i++) { 166 struct i2c_msg *i2c_msg = &i2c_msgs[i]; 167 168 if (i2c_msgs[i].flags & I2C_M_RD) { 169 memcpy(i2c_msg->buf, in_data, i2c_msg->len); 170 in_data += i2c_msg->len; 171 } 172 } 173 174 return 0; 175 } 176 177 static int ec_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg i2c_msgs[], 178 int num) 179 { 180 struct ec_i2c_device *bus = adap->algo_data; 181 struct device *dev = bus->dev; 182 const u16 bus_num = bus->remote_bus; 183 int request_len; 184 int response_len; 185 int result; 186 struct cros_ec_command msg = { }; 187 188 request_len = ec_i2c_count_message(i2c_msgs, num); 189 if (request_len < 0) { 190 dev_warn(dev, "Error constructing message %d\n", request_len); 191 return request_len; 192 } 193 194 response_len = ec_i2c_count_response(i2c_msgs, num); 195 if (response_len < 0) { 196 /* Unexpected; no errors should come when NULL response */ 197 dev_warn(dev, "Error preparing response %d\n", response_len); 198 return response_len; 199 } 200 201 result = ec_i2c_construct_message(msg.outdata, i2c_msgs, num, bus_num); 202 if (result) 203 return result; 204 205 msg.version = 0; 206 msg.command = EC_CMD_I2C_PASSTHRU; 207 msg.outsize = request_len; 208 msg.insize = response_len; 209 210 result = cros_ec_cmd_xfer(bus->ec, &msg); 211 if (result < 0) 212 return result; 213 214 result = ec_i2c_parse_response(msg.indata, i2c_msgs, &num); 215 if (result < 0) 216 return result; 217 218 /* Indicate success by saying how many messages were sent */ 219 return num; 220 } 221 222 static u32 ec_i2c_functionality(struct i2c_adapter *adap) 223 { 224 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL; 225 } 226 227 static const struct i2c_algorithm ec_i2c_algorithm = { 228 .master_xfer = ec_i2c_xfer, 229 .functionality = ec_i2c_functionality, 230 }; 231 232 static int ec_i2c_probe(struct platform_device *pdev) 233 { 234 struct device_node *np = pdev->dev.of_node; 235 struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent); 236 struct device *dev = &pdev->dev; 237 struct ec_i2c_device *bus = NULL; 238 u32 remote_bus; 239 int err; 240 241 if (!ec->cmd_xfer) { 242 dev_err(dev, "Missing sendrecv\n"); 243 return -EINVAL; 244 } 245 246 bus = devm_kzalloc(dev, sizeof(*bus), GFP_KERNEL); 247 if (bus == NULL) 248 return -ENOMEM; 249 250 err = of_property_read_u32(np, "google,remote-bus", &remote_bus); 251 if (err) { 252 dev_err(dev, "Couldn't read remote-bus property\n"); 253 return err; 254 } 255 bus->remote_bus = remote_bus; 256 257 bus->ec = ec; 258 bus->dev = dev; 259 260 bus->adap.owner = THIS_MODULE; 261 strlcpy(bus->adap.name, "cros-ec-i2c-tunnel", sizeof(bus->adap.name)); 262 bus->adap.algo = &ec_i2c_algorithm; 263 bus->adap.algo_data = bus; 264 bus->adap.dev.parent = &pdev->dev; 265 bus->adap.dev.of_node = np; 266 bus->adap.retries = I2C_MAX_RETRIES; 267 268 err = i2c_add_adapter(&bus->adap); 269 if (err) { 270 dev_err(dev, "cannot register i2c adapter\n"); 271 return err; 272 } 273 platform_set_drvdata(pdev, bus); 274 275 return err; 276 } 277 278 static int ec_i2c_remove(struct platform_device *dev) 279 { 280 struct ec_i2c_device *bus = platform_get_drvdata(dev); 281 282 i2c_del_adapter(&bus->adap); 283 284 return 0; 285 } 286 287 #ifdef CONFIG_OF 288 static const struct of_device_id cros_ec_i2c_of_match[] = { 289 { .compatible = "google,cros-ec-i2c-tunnel" }, 290 {}, 291 }; 292 MODULE_DEVICE_TABLE(of, cros_ec_i2c_of_match); 293 #endif 294 295 static struct platform_driver ec_i2c_tunnel_driver = { 296 .probe = ec_i2c_probe, 297 .remove = ec_i2c_remove, 298 .driver = { 299 .name = "cros-ec-i2c-tunnel", 300 .of_match_table = of_match_ptr(cros_ec_i2c_of_match), 301 }, 302 }; 303 304 module_platform_driver(ec_i2c_tunnel_driver); 305 306 MODULE_LICENSE("GPL"); 307 MODULE_DESCRIPTION("EC I2C tunnel driver"); 308 MODULE_ALIAS("platform:cros-ec-i2c-tunnel"); 309