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_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");