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 alloc_size; 186 int result; 187 struct cros_ec_command *msg; 188 189 request_len = ec_i2c_count_message(i2c_msgs, num); 190 if (request_len < 0) { 191 dev_warn(dev, "Error constructing message %d\n", request_len); 192 return request_len; 193 } 194 195 response_len = ec_i2c_count_response(i2c_msgs, num); 196 if (response_len < 0) { 197 /* Unexpected; no errors should come when NULL response */ 198 dev_warn(dev, "Error preparing response %d\n", response_len); 199 return response_len; 200 } 201 202 alloc_size = max(request_len, response_len); 203 msg = kmalloc(sizeof(*msg) + alloc_size, GFP_KERNEL); 204 if (!msg) 205 return -ENOMEM; 206 207 result = ec_i2c_construct_message(msg->data, i2c_msgs, num, bus_num); 208 if (result) { 209 dev_err(dev, "Error constructing EC i2c message %d\n", result); 210 goto exit; 211 } 212 213 msg->version = 0; 214 msg->command = EC_CMD_I2C_PASSTHRU; 215 msg->outsize = request_len; 216 msg->insize = response_len; 217 218 result = cros_ec_cmd_xfer(bus->ec, msg); 219 if (result < 0) { 220 dev_err(dev, "Error transferring EC i2c message %d\n", result); 221 goto exit; 222 } 223 224 result = ec_i2c_parse_response(msg->data, i2c_msgs, &num); 225 if (result < 0) { 226 dev_err(dev, "Error parsing EC i2c message %d\n", result); 227 goto exit; 228 } 229 230 /* Indicate success by saying how many messages were sent */ 231 result = num; 232 exit: 233 kfree(msg); 234 return result; 235 } 236 237 static u32 ec_i2c_functionality(struct i2c_adapter *adap) 238 { 239 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL; 240 } 241 242 static const struct i2c_algorithm ec_i2c_algorithm = { 243 .master_xfer = ec_i2c_xfer, 244 .functionality = ec_i2c_functionality, 245 }; 246 247 static int ec_i2c_probe(struct platform_device *pdev) 248 { 249 struct device_node *np = pdev->dev.of_node; 250 struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent); 251 struct device *dev = &pdev->dev; 252 struct ec_i2c_device *bus = NULL; 253 u32 remote_bus; 254 int err; 255 256 if (!ec->cmd_xfer) { 257 dev_err(dev, "Missing sendrecv\n"); 258 return -EINVAL; 259 } 260 261 bus = devm_kzalloc(dev, sizeof(*bus), GFP_KERNEL); 262 if (bus == NULL) 263 return -ENOMEM; 264 265 err = of_property_read_u32(np, "google,remote-bus", &remote_bus); 266 if (err) { 267 dev_err(dev, "Couldn't read remote-bus property\n"); 268 return err; 269 } 270 bus->remote_bus = remote_bus; 271 272 bus->ec = ec; 273 bus->dev = dev; 274 275 bus->adap.owner = THIS_MODULE; 276 strlcpy(bus->adap.name, "cros-ec-i2c-tunnel", sizeof(bus->adap.name)); 277 bus->adap.algo = &ec_i2c_algorithm; 278 bus->adap.algo_data = bus; 279 bus->adap.dev.parent = &pdev->dev; 280 bus->adap.dev.of_node = np; 281 bus->adap.retries = I2C_MAX_RETRIES; 282 283 err = i2c_add_adapter(&bus->adap); 284 if (err) { 285 dev_err(dev, "cannot register i2c adapter\n"); 286 return err; 287 } 288 platform_set_drvdata(pdev, bus); 289 290 return err; 291 } 292 293 static int ec_i2c_remove(struct platform_device *dev) 294 { 295 struct ec_i2c_device *bus = platform_get_drvdata(dev); 296 297 i2c_del_adapter(&bus->adap); 298 299 return 0; 300 } 301 302 #ifdef CONFIG_OF 303 static const struct of_device_id cros_ec_i2c_of_match[] = { 304 { .compatible = "google,cros-ec-i2c-tunnel" }, 305 {}, 306 }; 307 MODULE_DEVICE_TABLE(of, cros_ec_i2c_of_match); 308 #endif 309 310 static struct platform_driver ec_i2c_tunnel_driver = { 311 .probe = ec_i2c_probe, 312 .remove = ec_i2c_remove, 313 .driver = { 314 .name = "cros-ec-i2c-tunnel", 315 .of_match_table = of_match_ptr(cros_ec_i2c_of_match), 316 }, 317 }; 318 319 module_platform_driver(ec_i2c_tunnel_driver); 320 321 MODULE_LICENSE("GPL"); 322 MODULE_DESCRIPTION("EC I2C tunnel driver"); 323 MODULE_ALIAS("platform:cros-ec-i2c-tunnel"); 324