drivers/i2c/busses/i2c-cros-ec-tunnel.c

   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 = &params->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_NAK)
 158                 return -ENXIO;
 159         else if (resp->i2c_status & EC_I2C_STATUS_ERROR)
 160                 return -EIO;
 161
 162         /* Other side could send us back fewer messages, but not more */
 163         if (resp->num_msgs > *num)
 164                 return -EPROTO;
 165         *num = resp->num_msgs;
 166
 167         for (i = 0; i < *num; i++) {
 168                 struct i2c_msg *i2c_msg = &i2c_msgs[i];
 169
 170                 if (i2c_msgs[i].flags & I2C_M_RD) {
 171                         memcpy(i2c_msg->buf, in_data, i2c_msg->len);
 172                         in_data += i2c_msg->len;
 173                 }
 174         }
 175
 176         return 0;
 177 }
 178
 179 static int ec_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg i2c_msgs[],
 180                        int num)
 181 {
 182         struct ec_i2c_device *bus = adap->algo_data;
 183         struct device *dev = bus->dev;
 184         const u16 bus_num = bus->remote_bus;
 185         int request_len;
 186         int response_len;
 187         int alloc_size;
 188         int result;
 189         struct cros_ec_command *msg;
 190
 191         request_len = ec_i2c_count_message(i2c_msgs, num);
 192         if (request_len < 0) {
 193                 dev_warn(dev, "Error constructing message %d\n", request_len);
 194                 return request_len;
 195         }
 196
 197         response_len = ec_i2c_count_response(i2c_msgs, num);
 198         if (response_len < 0) {
 199                 /* Unexpected; no errors should come when NULL response */
 200                 dev_warn(dev, "Error preparing response %d\n", response_len);
 201                 return response_len;
 202         }
 203
 204         alloc_size = max(request_len, response_len);
 205         msg = kmalloc(sizeof(*msg) + alloc_size, GFP_KERNEL);
 206         if (!msg)
 207                 return -ENOMEM;
 208
 209         result = ec_i2c_construct_message(msg->data, i2c_msgs, num, bus_num);
 210         if (result) {
 211                 dev_err(dev, "Error constructing EC i2c message %d\n", result);
 212                 goto exit;
 213         }
 214
 215         msg->version = 0;
 216         msg->command = EC_CMD_I2C_PASSTHRU;
 217         msg->outsize = request_len;
 218         msg->insize = response_len;
 219
 220         result = cros_ec_cmd_xfer_status(bus->ec, msg);
 221         if (result < 0) {
 222                 dev_err(dev, "Error transferring EC i2c message %d\n", result);
 223                 goto exit;
 224         }
 225
 226         result = ec_i2c_parse_response(msg->data, i2c_msgs, &num);
 227         if (result < 0)
 228                 goto exit;
 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                 return err;
 286         platform_set_drvdata(pdev, bus);
 287
 288         return err;
 289 }
 290
 291 static int ec_i2c_remove(struct platform_device *dev)
 292 {
 293         struct ec_i2c_device *bus = platform_get_drvdata(dev);
 294
 295         i2c_del_adapter(&bus->adap);
 296
 297         return 0;
 298 }
 299
 300 #ifdef CONFIG_OF
 301 static const struct of_device_id cros_ec_i2c_of_match[] = {
 302         { .compatible = "google,cros-ec-i2c-tunnel" },
 303         {},
 304 };
 305 MODULE_DEVICE_TABLE(of, cros_ec_i2c_of_match);
 306 #endif
 307
 308 static struct platform_driver ec_i2c_tunnel_driver = {
 309         .probe = ec_i2c_probe,
 310         .remove = ec_i2c_remove,
 311         .driver = {
 312                 .name = "cros-ec-i2c-tunnel",
 313                 .of_match_table = of_match_ptr(cros_ec_i2c_of_match),
 314         },
 315 };
 316
 317 module_platform_driver(ec_i2c_tunnel_driver);
 318
 319 MODULE_LICENSE("GPL");
 320 MODULE_DESCRIPTION("EC I2C tunnel driver");
 321 MODULE_ALIAS("platform:cros-ec-i2c-tunnel");