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 /**
  20  * struct ec_i2c_device - Driver data for I2C tunnel
  21  *
  22  * @dev: Device node
  23  * @adap: I2C adapter
  24  * @ec: Pointer to EC device
  25  * @remote_bus: The EC bus number we tunnel to on the other side.
  26  * @request_buf: Buffer for transmitting data; we expect most transfers to fit.
  27  * @response_buf: Buffer for receiving data; we expect most transfers to fit.
  28  */
  29
  30 struct ec_i2c_device {
  31         struct device *dev;
  32         struct i2c_adapter adap;
  33         struct cros_ec_device *ec;
  34
  35         u16 remote_bus;
  36
  37         u8 request_buf[256];
  38         u8 response_buf[256];
  39 };
  40
  41 /**
  42  * ec_i2c_count_message - Count bytes needed for ec_i2c_construct_message
  43  *
  44  * @i2c_msgs: The i2c messages to read
  45  * @num: The number of i2c messages.
  46  *
  47  * Returns the number of bytes the messages will take up.
  48  */
  49 static int ec_i2c_count_message(const struct i2c_msg i2c_msgs[], int num)
  50 {
  51         int i;
  52         int size;
  53
  54         size = sizeof(struct ec_params_i2c_passthru);
  55         size += num * sizeof(struct ec_params_i2c_passthru_msg);
  56         for (i = 0; i < num; i++)
  57                 if (!(i2c_msgs[i].flags & I2C_M_RD))
  58                         size += i2c_msgs[i].len;
  59
  60         return size;
  61 }
  62
  63 /**
  64  * ec_i2c_construct_message - construct a message to go to the EC
  65  *
  66  * This function effectively stuffs the standard i2c_msg format of Linux into
  67  * a format that the EC understands.
  68  *
  69  * @buf: The buffer to fill.  We assume that the buffer is big enough.
  70  * @i2c_msgs: The i2c messages to read.
  71  * @num: The number of i2c messages.
  72  * @bus_num: The remote bus number we want to talk to.
  73  *
  74  * Returns 0 or a negative error number.
  75  */
  76 static int ec_i2c_construct_message(u8 *buf, const struct i2c_msg i2c_msgs[],
  77                                     int num, u16 bus_num)
  78 {
  79         struct ec_params_i2c_passthru *params;
  80         u8 *out_data;
  81         int i;
  82
  83         out_data = buf + sizeof(struct ec_params_i2c_passthru) +
  84                    num * sizeof(struct ec_params_i2c_passthru_msg);
  85
  86         params = (struct ec_params_i2c_passthru *)buf;
  87         params->port = bus_num;
  88         params->num_msgs = num;
  89         for (i = 0; i < num; i++) {
  90                 const struct i2c_msg *i2c_msg = &i2c_msgs[i];
  91                 struct ec_params_i2c_passthru_msg *msg = &params->msg[i];
  92
  93                 msg->len = i2c_msg->len;
  94                 msg->addr_flags = i2c_msg->addr;
  95
  96                 if (i2c_msg->flags & I2C_M_TEN)
  97                         msg->addr_flags |= EC_I2C_FLAG_10BIT;
  98
  99                 if (i2c_msg->flags & I2C_M_RD) {
 100                         msg->addr_flags |= EC_I2C_FLAG_READ;
 101                 } else {
 102                         memcpy(out_data, i2c_msg->buf, msg->len);
 103                         out_data += msg->len;
 104                 }
 105         }
 106
 107         return 0;
 108 }
 109
 110 /**
 111  * ec_i2c_count_response - Count bytes needed for ec_i2c_parse_response
 112  *
 113  * @i2c_msgs: The i2c messages to to fill up.
 114  * @num: The number of i2c messages expected.
 115  *
 116  * Returns the number of response bytes expeced.
 117  */
 118 static int ec_i2c_count_response(struct i2c_msg i2c_msgs[], int num)
 119 {
 120         int size;
 121         int i;
 122
 123         size = sizeof(struct ec_response_i2c_passthru);
 124         for (i = 0; i < num; i++)
 125                 if (i2c_msgs[i].flags & I2C_M_RD)
 126                         size += i2c_msgs[i].len;
 127
 128         return size;
 129 }
 130
 131 /**
 132  * ec_i2c_parse_response - Parse a response from the EC
 133  *
 134  * We'll take the EC's response and copy it back into msgs.
 135  *
 136  * @buf: The buffer to parse.
 137  * @i2c_msgs: The i2c messages to to fill up.
 138  * @num: The number of i2c messages; will be modified to include the actual
 139  *       number received.
 140  *
 141  * Returns 0 or a negative error number.
 142  */
 143 static int ec_i2c_parse_response(const u8 *buf, struct i2c_msg i2c_msgs[],
 144                                  int *num)
 145 {
 146         const struct ec_response_i2c_passthru *resp;
 147         const u8 *in_data;
 148         int i;
 149
 150         in_data = buf + sizeof(struct ec_response_i2c_passthru);
 151
 152         resp = (const struct ec_response_i2c_passthru *)buf;
 153         if (resp->i2c_status & EC_I2C_STATUS_TIMEOUT)
 154                 return -ETIMEDOUT;
 155         else if (resp->i2c_status & EC_I2C_STATUS_ERROR)
 156                 return -EREMOTEIO;
 157
 158         /* Other side could send us back fewer messages, but not more */
 159         if (resp->num_msgs > *num)
 160                 return -EPROTO;
 161         *num = resp->num_msgs;
 162
 163         for (i = 0; i < *num; i++) {
 164                 struct i2c_msg *i2c_msg = &i2c_msgs[i];
 165
 166                 if (i2c_msgs[i].flags & I2C_M_RD) {
 167                         memcpy(i2c_msg->buf, in_data, i2c_msg->len);
 168                         in_data += i2c_msg->len;
 169                 }
 170         }
 171
 172         return 0;
 173 }
 174
 175 static int ec_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg i2c_msgs[],
 176                        int num)
 177 {
 178         struct ec_i2c_device *bus = adap->algo_data;
 179         struct device *dev = bus->dev;
 180         const u16 bus_num = bus->remote_bus;
 181         int request_len;
 182         int response_len;
 183         u8 *request = NULL;
 184         u8 *response = NULL;
 185         int result;
 186
 187         request_len = ec_i2c_count_message(i2c_msgs, num);
 188         if (request_len < 0) {
 189                 dev_warn(dev, "Error constructing message %d\n", request_len);
 190                 result = request_len;
 191                 goto exit;
 192         }
 193         response_len = ec_i2c_count_response(i2c_msgs, num);
 194         if (response_len < 0) {
 195                 /* Unexpected; no errors should come when NULL response */
 196                 dev_warn(dev, "Error preparing response %d\n", response_len);
 197                 result = response_len;
 198                 goto exit;
 199         }
 200
 201         if (request_len <= ARRAY_SIZE(bus->request_buf)) {
 202                 request = bus->request_buf;
 203         } else {
 204                 request = kzalloc(request_len, GFP_KERNEL);
 205                 if (request == NULL) {
 206                         result = -ENOMEM;
 207                         goto exit;
 208                 }
 209         }
 210         if (response_len <= ARRAY_SIZE(bus->response_buf)) {
 211                 response = bus->response_buf;
 212         } else {
 213                 response = kzalloc(response_len, GFP_KERNEL);
 214                 if (response == NULL) {
 215                         result = -ENOMEM;
 216                         goto exit;
 217                 }
 218         }
 219
 220         ec_i2c_construct_message(request, i2c_msgs, num, bus_num);
 221         result = bus->ec->command_sendrecv(bus->ec, EC_CMD_I2C_PASSTHRU,
 222                                            request, request_len,
 223                                            response, response_len);
 224         if (result)
 225                 goto exit;
 226
 227         result = ec_i2c_parse_response(response, i2c_msgs, &num);
 228         if (result < 0)
 229                 goto exit;
 230
 231         /* Indicate success by saying how many messages were sent */
 232         result = num;
 233 exit:
 234         if (request != bus->request_buf)
 235                 kfree(request);
 236         if (response != bus->response_buf)
 237                 kfree(response);
 238
 239         return result;
 240 }
 241
 242 static u32 ec_i2c_functionality(struct i2c_adapter *adap)
 243 {
 244         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 245 }
 246
 247 static const struct i2c_algorithm ec_i2c_algorithm = {
 248         .master_xfer    = ec_i2c_xfer,
 249         .functionality  = ec_i2c_functionality,
 250 };
 251
 252 static int ec_i2c_probe(struct platform_device *pdev)
 253 {
 254         struct device_node *np = pdev->dev.of_node;
 255         struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
 256         struct device *dev = &pdev->dev;
 257         struct ec_i2c_device *bus = NULL;
 258         u32 remote_bus;
 259         int err;
 260
 261         if (!ec->command_sendrecv) {
 262                 dev_err(dev, "Missing sendrecv\n");
 263                 return -EINVAL;
 264         }
 265
 266         bus = devm_kzalloc(dev, sizeof(*bus), GFP_KERNEL);
 267         if (bus == NULL)
 268                 return -ENOMEM;
 269
 270         err = of_property_read_u32(np, "google,remote-bus", &remote_bus);
 271         if (err) {
 272                 dev_err(dev, "Couldn't read remote-bus property\n");
 273                 return err;
 274         }
 275         bus->remote_bus = remote_bus;
 276
 277         bus->ec = ec;
 278         bus->dev = dev;
 279
 280         bus->adap.owner = THIS_MODULE;
 281         strlcpy(bus->adap.name, "cros-ec-i2c-tunnel", sizeof(bus->adap.name));
 282         bus->adap.algo = &ec_i2c_algorithm;
 283         bus->adap.algo_data = bus;
 284         bus->adap.dev.parent = &pdev->dev;
 285         bus->adap.dev.of_node = np;
 286
 287         err = i2c_add_adapter(&bus->adap);
 288         if (err) {
 289                 dev_err(dev, "cannot register i2c adapter\n");
 290                 return err;
 291         }
 292         platform_set_drvdata(pdev, bus);
 293
 294         return err;
 295 }
 296
 297 static int ec_i2c_remove(struct platform_device *dev)
 298 {
 299         struct ec_i2c_device *bus = platform_get_drvdata(dev);
 300
 301         i2c_del_adapter(&bus->adap);
 302
 303         return 0;
 304 }
 305
 306 static struct platform_driver ec_i2c_tunnel_driver = {
 307         .probe = ec_i2c_probe,
 308         .remove = ec_i2c_remove,
 309         .driver = {
 310                 .name = "cros-ec-i2c-tunnel",
 311         },
 312 };
 313
 314 module_platform_driver(ec_i2c_tunnel_driver);
 315
 316 MODULE_LICENSE("GPL");
 317 MODULE_DESCRIPTION("EC I2C tunnel driver");
 318 MODULE_ALIAS("platform:cros-ec-i2c-tunnel");