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

   1 // SPDX-License-Identifier: GPL-2.0+
   2 // Expose an I2C passthrough to the ChromeOS EC.
   3 //
   4 // Copyright (C) 2013 Google, Inc.
   5
   6 #include <linux/module.h>
   7 #include <linux/i2c.h>
   8 #include <linux/platform_data/cros_ec_commands.h>
   9 #include <linux/platform_data/cros_ec_proto.h>
  10 #include <linux/platform_device.h>
  11 #include <linux/slab.h>
  12
  13 #define I2C_MAX_RETRIES 3
  14
  15 /**
  16  * struct ec_i2c_device - Driver data for I2C tunnel
  17  *
  18  * @dev: Device node
  19  * @adap: I2C adapter
  20  * @ec: Pointer to EC device
  21  * @remote_bus: The EC bus number we tunnel to on the other side.
  22  * @request_buf: Buffer for transmitting data; we expect most transfers to fit.
  23  * @response_buf: Buffer for receiving data; we expect most transfers to fit.
  24  */
  25
  26 struct ec_i2c_device {
  27         struct device *dev;
  28         struct i2c_adapter adap;
  29         struct cros_ec_device *ec;
  30
  31         u16 remote_bus;
  32
  33         u8 request_buf[256];
  34         u8 response_buf[256];
  35 };
  36
  37 /**
  38  * ec_i2c_count_message - Count bytes needed for ec_i2c_construct_message
  39  *
  40  * @i2c_msgs: The i2c messages to read
  41  * @num: The number of i2c messages.
  42  *
  43  * Returns the number of bytes the messages will take up.
  44  */
  45 static int ec_i2c_count_message(const struct i2c_msg i2c_msgs[], int num)
  46 {
  47         int i;
  48         int size;
  49
  50         size = sizeof(struct ec_params_i2c_passthru);
  51         size += num * sizeof(struct ec_params_i2c_passthru_msg);
  52         for (i = 0; i < num; i++)
  53                 if (!(i2c_msgs[i].flags & I2C_M_RD))
  54                         size += i2c_msgs[i].len;
  55
  56         return size;
  57 }
  58
  59 /**
  60  * ec_i2c_construct_message - construct a message to go to the EC
  61  *
  62  * This function effectively stuffs the standard i2c_msg format of Linux into
  63  * a format that the EC understands.
  64  *
  65  * @buf: The buffer to fill.  We assume that the buffer is big enough.
  66  * @i2c_msgs: The i2c messages to read.
  67  * @num: The number of i2c messages.
  68  * @bus_num: The remote bus number we want to talk to.
  69  *
  70  * Returns 0 or a negative error number.
  71  */
  72 static int ec_i2c_construct_message(u8 *buf, const struct i2c_msg i2c_msgs[],
  73                                     int num, u16 bus_num)
  74 {
  75         struct ec_params_i2c_passthru *params;
  76         u8 *out_data;
  77         int i;
  78
  79         out_data = buf + sizeof(struct ec_params_i2c_passthru) +
  80                    num * sizeof(struct ec_params_i2c_passthru_msg);
  81
  82         params = (struct ec_params_i2c_passthru *)buf;
  83         params->port = bus_num;
  84         params->num_msgs = num;
  85         for (i = 0; i < num; i++) {
  86                 const struct i2c_msg *i2c_msg = &i2c_msgs[i];
  87                 struct ec_params_i2c_passthru_msg *msg = &params->msg[i];
  88
  89                 msg->len = i2c_msg->len;
  90                 msg->addr_flags = i2c_msg->addr;
  91
  92                 if (i2c_msg->flags & I2C_M_TEN)
  93                         return -EINVAL;
  94
  95                 if (i2c_msg->flags & I2C_M_RD) {
  96                         msg->addr_flags |= EC_I2C_FLAG_READ;
  97                 } else {
  98                         memcpy(out_data, i2c_msg->buf, msg->len);
  99                         out_data += msg->len;
 100                 }
 101         }
 102
 103         return 0;
 104 }
 105
 106 /**
 107  * ec_i2c_count_response - Count bytes needed for ec_i2c_parse_response
 108  *
 109  * @i2c_msgs: The i2c messages to to fill up.
 110  * @num: The number of i2c messages expected.
 111  *
 112  * Returns the number of response bytes expeced.
 113  */
 114 static int ec_i2c_count_response(struct i2c_msg i2c_msgs[], int num)
 115 {
 116         int size;
 117         int i;
 118
 119         size = sizeof(struct ec_response_i2c_passthru);
 120         for (i = 0; i < num; i++)
 121                 if (i2c_msgs[i].flags & I2C_M_RD)
 122                         size += i2c_msgs[i].len;
 123
 124         return size;
 125 }
 126
 127 /**
 128  * ec_i2c_parse_response - Parse a response from the EC
 129  *
 130  * We'll take the EC's response and copy it back into msgs.
 131  *
 132  * @buf: The buffer to parse.
 133  * @i2c_msgs: The i2c messages to to fill up.
 134  * @num: The number of i2c messages; will be modified to include the actual
 135  *       number received.
 136  *
 137  * Returns 0 or a negative error number.
 138  */
 139 static int ec_i2c_parse_response(const u8 *buf, struct i2c_msg i2c_msgs[],
 140                                  int *num)
 141 {
 142         const struct ec_response_i2c_passthru *resp;
 143         const u8 *in_data;
 144         int i;
 145
 146         in_data = buf + sizeof(struct ec_response_i2c_passthru);
 147
 148         resp = (const struct ec_response_i2c_passthru *)buf;
 149         if (resp->i2c_status & EC_I2C_STATUS_TIMEOUT)
 150                 return -ETIMEDOUT;
 151         else if (resp->i2c_status & EC_I2C_STATUS_NAK)
 152                 return -ENXIO;
 153         else if (resp->i2c_status & EC_I2C_STATUS_ERROR)
 154                 return -EIO;
 155
 156         /* Other side could send us back fewer messages, but not more */
 157         if (resp->num_msgs > *num)
 158                 return -EPROTO;
 159         *num = resp->num_msgs;
 160
 161         for (i = 0; i < *num; i++) {
 162                 struct i2c_msg *i2c_msg = &i2c_msgs[i];
 163
 164                 if (i2c_msgs[i].flags & I2C_M_RD) {
 165                         memcpy(i2c_msg->buf, in_data, i2c_msg->len);
 166                         in_data += i2c_msg->len;
 167                 }
 168         }
 169
 170         return 0;
 171 }
 172
 173 static int ec_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg i2c_msgs[],
 174                        int num)
 175 {
 176         struct ec_i2c_device *bus = adap->algo_data;
 177         struct device *dev = bus->dev;
 178         const u16 bus_num = bus->remote_bus;
 179         int request_len;
 180         int response_len;
 181         int alloc_size;
 182         int result;
 183         struct cros_ec_command *msg;
 184
 185         request_len = ec_i2c_count_message(i2c_msgs, num);
 186         if (request_len < 0) {
 187                 dev_warn(dev, "Error constructing message %d\n", request_len);
 188                 return request_len;
 189         }
 190
 191         response_len = ec_i2c_count_response(i2c_msgs, num);
 192         if (response_len < 0) {
 193                 /* Unexpected; no errors should come when NULL response */
 194                 dev_warn(dev, "Error preparing response %d\n", response_len);
 195                 return response_len;
 196         }
 197
 198         alloc_size = max(request_len, response_len);
 199         msg = kmalloc(sizeof(*msg) + alloc_size, GFP_KERNEL);
 200         if (!msg)
 201                 return -ENOMEM;
 202
 203         result = ec_i2c_construct_message(msg->data, i2c_msgs, num, bus_num);
 204         if (result) {
 205                 dev_err(dev, "Error constructing EC i2c message %d\n", result);
 206                 goto exit;
 207         }
 208
 209         msg->version = 0;
 210         msg->command = EC_CMD_I2C_PASSTHRU;
 211         msg->outsize = request_len;
 212         msg->insize = response_len;
 213
 214         result = cros_ec_cmd_xfer_status(bus->ec, msg);
 215         if (result < 0) {
 216                 dev_err(dev, "Error transferring EC i2c message %d\n", result);
 217                 goto exit;
 218         }
 219
 220         result = ec_i2c_parse_response(msg->data, i2c_msgs, &num);
 221         if (result < 0)
 222                 goto exit;
 223
 224         /* Indicate success by saying how many messages were sent */
 225         result = num;
 226 exit:
 227         kfree(msg);
 228         return result;
 229 }
 230
 231 static u32 ec_i2c_functionality(struct i2c_adapter *adap)
 232 {
 233         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 234 }
 235
 236 static const struct i2c_algorithm ec_i2c_algorithm = {
 237         .master_xfer    = ec_i2c_xfer,
 238         .functionality  = ec_i2c_functionality,
 239 };
 240
 241 static int ec_i2c_probe(struct platform_device *pdev)
 242 {
 243         struct device_node *np = pdev->dev.of_node;
 244         struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
 245         struct device *dev = &pdev->dev;
 246         struct ec_i2c_device *bus = NULL;
 247         u32 remote_bus;
 248         int err;
 249
 250         if (!ec->cmd_xfer) {
 251                 dev_err(dev, "Missing sendrecv\n");
 252                 return -EINVAL;
 253         }
 254
 255         bus = devm_kzalloc(dev, sizeof(*bus), GFP_KERNEL);
 256         if (bus == NULL)
 257                 return -ENOMEM;
 258
 259         err = of_property_read_u32(np, "google,remote-bus", &remote_bus);
 260         if (err) {
 261                 dev_err(dev, "Couldn't read remote-bus property\n");
 262                 return err;
 263         }
 264         bus->remote_bus = remote_bus;
 265
 266         bus->ec = ec;
 267         bus->dev = dev;
 268
 269         bus->adap.owner = THIS_MODULE;
 270         strlcpy(bus->adap.name, "cros-ec-i2c-tunnel", sizeof(bus->adap.name));
 271         bus->adap.algo = &ec_i2c_algorithm;
 272         bus->adap.algo_data = bus;
 273         bus->adap.dev.parent = &pdev->dev;
 274         bus->adap.dev.of_node = np;
 275         bus->adap.retries = I2C_MAX_RETRIES;
 276
 277         err = i2c_add_adapter(&bus->adap);
 278         if (err)
 279                 return err;
 280         platform_set_drvdata(pdev, bus);
 281
 282         return err;
 283 }
 284
 285 static int ec_i2c_remove(struct platform_device *dev)
 286 {
 287         struct ec_i2c_device *bus = platform_get_drvdata(dev);
 288
 289         i2c_del_adapter(&bus->adap);
 290
 291         return 0;
 292 }
 293
 294 #ifdef CONFIG_OF
 295 static const struct of_device_id cros_ec_i2c_of_match[] = {
 296         { .compatible = "google,cros-ec-i2c-tunnel" },
 297         {},
 298 };
 299 MODULE_DEVICE_TABLE(of, cros_ec_i2c_of_match);
 300 #endif
 301
 302 static struct platform_driver ec_i2c_tunnel_driver = {
 303         .probe = ec_i2c_probe,
 304         .remove = ec_i2c_remove,
 305         .driver = {
 306                 .name = "cros-ec-i2c-tunnel",
 307                 .of_match_table = of_match_ptr(cros_ec_i2c_of_match),
 308         },
 309 };
 310
 311 module_platform_driver(ec_i2c_tunnel_driver);
 312
 313 MODULE_LICENSE("GPL");
 314 MODULE_DESCRIPTION("EC I2C tunnel driver");
 315 MODULE_ALIAS("platform:cros-ec-i2c-tunnel");