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/acpi.h>
   7 #include <linux/module.h>
   8 #include <linux/i2c.h>
   9 #include <linux/platform_data/cros_ec_commands.h>
  10 #include <linux/platform_data/cros_ec_proto.h>
  11 #include <linux/platform_device.h>
  12 #include <linux/slab.h>
  13
  14 #define I2C_MAX_RETRIES 3
  15
  16 /**
  17  * struct ec_i2c_device - Driver data for I2C tunnel
  18  *
  19  * @dev: Device node
  20  * @adap: I2C adapter
  21  * @ec: Pointer to EC device
  22  * @remote_bus: The EC bus number we tunnel to on the other side.
  23  * @request_buf: Buffer for transmitting data; we expect most transfers to fit.
  24  * @response_buf: Buffer for receiving data; we expect most transfers to fit.
  25  */
  26
  27 struct ec_i2c_device {
  28         struct device *dev;
  29         struct i2c_adapter adap;
  30         struct cros_ec_device *ec;
  31
  32         u16 remote_bus;
  33
  34         u8 request_buf[256];
  35         u8 response_buf[256];
  36 };
  37
  38 /**
  39  * ec_i2c_count_message - Count bytes needed for ec_i2c_construct_message
  40  *
  41  * @i2c_msgs: The i2c messages to read
  42  * @num: The number of i2c messages.
  43  *
  44  * Returns the number of bytes the messages will take up.
  45  */
  46 static int ec_i2c_count_message(const struct i2c_msg i2c_msgs[], int num)
  47 {
  48         int i;
  49         int size;
  50
  51         size = sizeof(struct ec_params_i2c_passthru);
  52         size += num * sizeof(struct ec_params_i2c_passthru_msg);
  53         for (i = 0; i < num; i++)
  54                 if (!(i2c_msgs[i].flags & I2C_M_RD))
  55                         size += i2c_msgs[i].len;
  56
  57         return size;
  58 }
  59
  60 /**
  61  * ec_i2c_construct_message - construct a message to go to the EC
  62  *
  63  * This function effectively stuffs the standard i2c_msg format of Linux into
  64  * a format that the EC understands.
  65  *
  66  * @buf: The buffer to fill.  We assume that the buffer is big enough.
  67  * @i2c_msgs: The i2c messages to read.
  68  * @num: The number of i2c messages.
  69  * @bus_num: The remote bus number we want to talk to.
  70  *
  71  * Returns 0 or a negative error number.
  72  */
  73 static int ec_i2c_construct_message(u8 *buf, const struct i2c_msg i2c_msgs[],
  74                                     int num, u16 bus_num)
  75 {
  76         struct ec_params_i2c_passthru *params;
  77         u8 *out_data;
  78         int i;
  79
  80         out_data = buf + sizeof(struct ec_params_i2c_passthru) +
  81                    num * sizeof(struct ec_params_i2c_passthru_msg);
  82
  83         params = (struct ec_params_i2c_passthru *)buf;
  84         params->port = bus_num;
  85         params->num_msgs = num;
  86         for (i = 0; i < num; i++) {
  87                 const struct i2c_msg *i2c_msg = &i2c_msgs[i];
  88                 struct ec_params_i2c_passthru_msg *msg = &params->msg[i];
  89
  90                 msg->len = i2c_msg->len;
  91                 msg->addr_flags = i2c_msg->addr;
  92
  93                 if (i2c_msg->flags & I2C_M_TEN)
  94                         return -EINVAL;
  95
  96                 if (i2c_msg->flags & I2C_M_RD) {
  97                         msg->addr_flags |= EC_I2C_FLAG_READ;
  98                 } else {
  99                         memcpy(out_data, i2c_msg->buf, msg->len);
 100                         out_data += msg->len;
 101                 }
 102         }
 103
 104         return 0;
 105 }
 106
 107 /**
 108  * ec_i2c_count_response - Count bytes needed for ec_i2c_parse_response
 109  *
 110  * @i2c_msgs: The i2c messages to to fill up.
 111  * @num: The number of i2c messages expected.
 112  *
 113  * Returns the number of response bytes expeced.
 114  */
 115 static int ec_i2c_count_response(struct i2c_msg i2c_msgs[], int num)
 116 {
 117         int size;
 118         int i;
 119
 120         size = sizeof(struct ec_response_i2c_passthru);
 121         for (i = 0; i < num; i++)
 122                 if (i2c_msgs[i].flags & I2C_M_RD)
 123                         size += i2c_msgs[i].len;
 124
 125         return size;
 126 }
 127
 128 /**
 129  * ec_i2c_parse_response - Parse a response from the EC
 130  *
 131  * We'll take the EC's response and copy it back into msgs.
 132  *
 133  * @buf: The buffer to parse.
 134  * @i2c_msgs: The i2c messages to to fill up.
 135  * @num: The number of i2c messages; will be modified to include the actual
 136  *       number received.
 137  *
 138  * Returns 0 or a negative error number.
 139  */
 140 static int ec_i2c_parse_response(const u8 *buf, struct i2c_msg i2c_msgs[],
 141                                  int *num)
 142 {
 143         const struct ec_response_i2c_passthru *resp;
 144         const u8 *in_data;
 145         int i;
 146
 147         in_data = buf + sizeof(struct ec_response_i2c_passthru);
 148
 149         resp = (const struct ec_response_i2c_passthru *)buf;
 150         if (resp->i2c_status & EC_I2C_STATUS_TIMEOUT)
 151                 return -ETIMEDOUT;
 152         else if (resp->i2c_status & EC_I2C_STATUS_NAK)
 153                 return -ENXIO;
 154         else if (resp->i2c_status & EC_I2C_STATUS_ERROR)
 155                 return -EIO;
 156
 157         /* Other side could send us back fewer messages, but not more */
 158         if (resp->num_msgs > *num)
 159                 return -EPROTO;
 160         *num = resp->num_msgs;
 161
 162         for (i = 0; i < *num; i++) {
 163                 struct i2c_msg *i2c_msg = &i2c_msgs[i];
 164
 165                 if (i2c_msgs[i].flags & I2C_M_RD) {
 166                         memcpy(i2c_msg->buf, in_data, i2c_msg->len);
 167                         in_data += i2c_msg->len;
 168                 }
 169         }
 170
 171         return 0;
 172 }
 173
 174 static int ec_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg i2c_msgs[],
 175                        int num)
 176 {
 177         struct ec_i2c_device *bus = adap->algo_data;
 178         struct device *dev = bus->dev;
 179         const u16 bus_num = bus->remote_bus;
 180         int request_len;
 181         int response_len;
 182         int alloc_size;
 183         int result;
 184         struct cros_ec_command *msg;
 185
 186         request_len = ec_i2c_count_message(i2c_msgs, num);
 187         if (request_len < 0) {
 188                 dev_warn(dev, "Error constructing message %d\n", request_len);
 189                 return request_len;
 190         }
 191
 192         response_len = ec_i2c_count_response(i2c_msgs, num);
 193         if (response_len < 0) {
 194                 /* Unexpected; no errors should come when NULL response */
 195                 dev_warn(dev, "Error preparing response %d\n", response_len);
 196                 return response_len;
 197         }
 198
 199         alloc_size = max(request_len, response_len);
 200         msg = kmalloc(sizeof(*msg) + alloc_size, GFP_KERNEL);
 201         if (!msg)
 202                 return -ENOMEM;
 203
 204         result = ec_i2c_construct_message(msg->data, i2c_msgs, num, bus_num);
 205         if (result) {
 206                 dev_err(dev, "Error constructing EC i2c message %d\n", result);
 207                 goto exit;
 208         }
 209
 210         msg->version = 0;
 211         msg->command = EC_CMD_I2C_PASSTHRU;
 212         msg->outsize = request_len;
 213         msg->insize = response_len;
 214
 215         result = cros_ec_cmd_xfer_status(bus->ec, msg);
 216         if (result < 0) {
 217                 dev_err(dev, "Error transferring EC i2c message %d\n", result);
 218                 goto exit;
 219         }
 220
 221         result = ec_i2c_parse_response(msg->data, i2c_msgs, &num);
 222         if (result < 0)
 223                 goto exit;
 224
 225         /* Indicate success by saying how many messages were sent */
 226         result = num;
 227 exit:
 228         kfree(msg);
 229         return result;
 230 }
 231
 232 static u32 ec_i2c_functionality(struct i2c_adapter *adap)
 233 {
 234         return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
 235 }
 236
 237 static const struct i2c_algorithm ec_i2c_algorithm = {
 238         .master_xfer    = ec_i2c_xfer,
 239         .functionality  = ec_i2c_functionality,
 240 };
 241
 242 static int ec_i2c_probe(struct platform_device *pdev)
 243 {
 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 = device_property_read_u32(dev, "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 = pdev->dev.of_node;
 275         bus->adap.retries = I2C_MAX_RETRIES;
 276         ACPI_COMPANION_SET(&bus->adap.dev, ACPI_COMPANION(&pdev->dev));
 277
 278         err = i2c_add_adapter(&bus->adap);
 279         if (err)
 280                 return err;
 281         platform_set_drvdata(pdev, bus);
 282
 283         return err;
 284 }
 285
 286 static int ec_i2c_remove(struct platform_device *dev)
 287 {
 288         struct ec_i2c_device *bus = platform_get_drvdata(dev);
 289
 290         i2c_del_adapter(&bus->adap);
 291
 292         return 0;
 293 }
 294
 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
 301 static const struct acpi_device_id cros_ec_i2c_tunnel_acpi_id[] = {
 302         { "GOOG0012", 0 },
 303         { }
 304 };
 305 MODULE_DEVICE_TABLE(acpi, cros_ec_i2c_tunnel_acpi_id);
 306
 307 static struct platform_driver ec_i2c_tunnel_driver = {
 308         .probe = ec_i2c_probe,
 309         .remove = ec_i2c_remove,
 310         .driver = {
 311                 .name = "cros-ec-i2c-tunnel",
 312                 .acpi_match_table = ACPI_PTR(cros_ec_i2c_tunnel_acpi_id),
 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");