Simon Glass | a17d94f | 2013-02-25 14:08:39 -0800 | [diff] [blame] | 1 | /* |
| 2 | * ChromeOS EC multi-function device (SPI) |
| 3 | * |
| 4 | * Copyright (C) 2012 Google, Inc |
| 5 | * |
| 6 | * This software is licensed under the terms of the GNU General Public |
| 7 | * License version 2, as published by the Free Software Foundation, and |
| 8 | * may be copied, distributed, and modified under those terms. |
| 9 | * |
| 10 | * This program is distributed in the hope that it will be useful, |
| 11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 13 | * GNU General Public License for more details. |
| 14 | */ |
| 15 | |
| 16 | #include <linux/delay.h> |
| 17 | #include <linux/kernel.h> |
| 18 | #include <linux/module.h> |
| 19 | #include <linux/mfd/cros_ec.h> |
| 20 | #include <linux/mfd/cros_ec_commands.h> |
| 21 | #include <linux/platform_device.h> |
| 22 | #include <linux/slab.h> |
| 23 | #include <linux/spi/spi.h> |
| 24 | |
| 25 | |
| 26 | /* The header byte, which follows the preamble */ |
| 27 | #define EC_MSG_HEADER 0xec |
| 28 | |
| 29 | /* |
| 30 | * Number of EC preamble bytes we read at a time. Since it takes |
| 31 | * about 400-500us for the EC to respond there is not a lot of |
| 32 | * point in tuning this. If the EC could respond faster then |
| 33 | * we could increase this so that might expect the preamble and |
| 34 | * message to occur in a single transaction. However, the maximum |
| 35 | * SPI transfer size is 256 bytes, so at 5MHz we need a response |
| 36 | * time of perhaps <320us (200 bytes / 1600 bits). |
| 37 | */ |
| 38 | #define EC_MSG_PREAMBLE_COUNT 32 |
| 39 | |
| 40 | /* |
| 41 | * We must get a response from the EC in 5ms. This is a very long |
| 42 | * time, but the flash write command can take 2-3ms. The EC command |
| 43 | * processing is currently not very fast (about 500us). We could |
| 44 | * look at speeding this up and making the flash write command a |
| 45 | * 'slow' command, requiring a GET_STATUS wait loop, like flash |
| 46 | * erase. |
| 47 | */ |
| 48 | #define EC_MSG_DEADLINE_MS 5 |
| 49 | |
| 50 | /* |
| 51 | * Time between raising the SPI chip select (for the end of a |
| 52 | * transaction) and dropping it again (for the next transaction). |
Derek Basehore | 49f91ac | 2013-11-18 11:30:48 +0100 | [diff] [blame] | 53 | * If we go too fast, the EC will miss the transaction. We know that we |
| 54 | * need at least 70 us with the 16 MHz STM32 EC, so go with 200 us to be |
| 55 | * safe. |
Simon Glass | a17d94f | 2013-02-25 14:08:39 -0800 | [diff] [blame] | 56 | */ |
Derek Basehore | 49f91ac | 2013-11-18 11:30:48 +0100 | [diff] [blame] | 57 | #define EC_SPI_RECOVERY_TIME_NS (200 * 1000) |
Simon Glass | a17d94f | 2013-02-25 14:08:39 -0800 | [diff] [blame] | 58 | |
| 59 | /** |
| 60 | * struct cros_ec_spi - information about a SPI-connected EC |
| 61 | * |
| 62 | * @spi: SPI device we are connected to |
| 63 | * @last_transfer_ns: time that we last finished a transfer, or 0 if there |
| 64 | * if no record |
| 65 | */ |
| 66 | struct cros_ec_spi { |
| 67 | struct spi_device *spi; |
| 68 | s64 last_transfer_ns; |
| 69 | }; |
| 70 | |
| 71 | static void debug_packet(struct device *dev, const char *name, u8 *ptr, |
| 72 | int len) |
| 73 | { |
| 74 | #ifdef DEBUG |
| 75 | int i; |
| 76 | |
| 77 | dev_dbg(dev, "%s: ", name); |
| 78 | for (i = 0; i < len; i++) |
Thierry Reding | 9e146f4 | 2013-11-18 11:30:49 +0100 | [diff] [blame] | 79 | pr_cont(" %02x", ptr[i]); |
| 80 | |
| 81 | pr_cont("\n"); |
Simon Glass | a17d94f | 2013-02-25 14:08:39 -0800 | [diff] [blame] | 82 | #endif |
| 83 | } |
| 84 | |
| 85 | /** |
| 86 | * cros_ec_spi_receive_response - Receive a response from the EC. |
| 87 | * |
| 88 | * This function has two phases: reading the preamble bytes (since if we read |
| 89 | * data from the EC before it is ready to send, we just get preamble) and |
| 90 | * reading the actual message. |
| 91 | * |
| 92 | * The received data is placed into ec_dev->din. |
| 93 | * |
| 94 | * @ec_dev: ChromeOS EC device |
| 95 | * @need_len: Number of message bytes we need to read |
| 96 | */ |
| 97 | static int cros_ec_spi_receive_response(struct cros_ec_device *ec_dev, |
| 98 | int need_len) |
| 99 | { |
| 100 | struct cros_ec_spi *ec_spi = ec_dev->priv; |
| 101 | struct spi_transfer trans; |
| 102 | struct spi_message msg; |
| 103 | u8 *ptr, *end; |
| 104 | int ret; |
| 105 | unsigned long deadline; |
| 106 | int todo; |
| 107 | |
| 108 | /* Receive data until we see the header byte */ |
| 109 | deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS); |
| 110 | do { |
| 111 | memset(&trans, '\0', sizeof(trans)); |
| 112 | trans.cs_change = 1; |
| 113 | trans.rx_buf = ptr = ec_dev->din; |
| 114 | trans.len = EC_MSG_PREAMBLE_COUNT; |
| 115 | |
| 116 | spi_message_init(&msg); |
| 117 | spi_message_add_tail(&trans, &msg); |
| 118 | ret = spi_sync(ec_spi->spi, &msg); |
| 119 | if (ret < 0) { |
| 120 | dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret); |
| 121 | return ret; |
| 122 | } |
| 123 | |
| 124 | for (end = ptr + EC_MSG_PREAMBLE_COUNT; ptr != end; ptr++) { |
| 125 | if (*ptr == EC_MSG_HEADER) { |
Geert Uytterhoeven | c34924b | 2013-05-08 23:37:45 +0200 | [diff] [blame] | 126 | dev_dbg(ec_dev->dev, "msg found at %zd\n", |
Simon Glass | a17d94f | 2013-02-25 14:08:39 -0800 | [diff] [blame] | 127 | ptr - ec_dev->din); |
| 128 | break; |
| 129 | } |
| 130 | } |
| 131 | |
| 132 | if (time_after(jiffies, deadline)) { |
| 133 | dev_warn(ec_dev->dev, "EC failed to respond in time\n"); |
| 134 | return -ETIMEDOUT; |
| 135 | } |
| 136 | } while (ptr == end); |
| 137 | |
| 138 | /* |
| 139 | * ptr now points to the header byte. Copy any valid data to the |
| 140 | * start of our buffer |
| 141 | */ |
| 142 | todo = end - ++ptr; |
| 143 | BUG_ON(todo < 0 || todo > ec_dev->din_size); |
| 144 | todo = min(todo, need_len); |
| 145 | memmove(ec_dev->din, ptr, todo); |
| 146 | ptr = ec_dev->din + todo; |
| 147 | dev_dbg(ec_dev->dev, "need %d, got %d bytes from preamble\n", |
| 148 | need_len, todo); |
| 149 | need_len -= todo; |
| 150 | |
| 151 | /* Receive data until we have it all */ |
| 152 | while (need_len > 0) { |
| 153 | /* |
| 154 | * We can't support transfers larger than the SPI FIFO size |
| 155 | * unless we have DMA. We don't have DMA on the ISP SPI ports |
| 156 | * for Exynos. We need a way of asking SPI driver for |
| 157 | * maximum-supported transfer size. |
| 158 | */ |
| 159 | todo = min(need_len, 256); |
Geert Uytterhoeven | c34924b | 2013-05-08 23:37:45 +0200 | [diff] [blame] | 160 | dev_dbg(ec_dev->dev, "loop, todo=%d, need_len=%d, ptr=%zd\n", |
Simon Glass | a17d94f | 2013-02-25 14:08:39 -0800 | [diff] [blame] | 161 | todo, need_len, ptr - ec_dev->din); |
| 162 | |
| 163 | memset(&trans, '\0', sizeof(trans)); |
| 164 | trans.cs_change = 1; |
| 165 | trans.rx_buf = ptr; |
| 166 | trans.len = todo; |
| 167 | spi_message_init(&msg); |
| 168 | spi_message_add_tail(&trans, &msg); |
| 169 | |
| 170 | /* send command to EC and read answer */ |
| 171 | BUG_ON((u8 *)trans.rx_buf - ec_dev->din + todo > |
| 172 | ec_dev->din_size); |
| 173 | ret = spi_sync(ec_spi->spi, &msg); |
| 174 | if (ret < 0) { |
| 175 | dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret); |
| 176 | return ret; |
| 177 | } |
| 178 | |
| 179 | debug_packet(ec_dev->dev, "interim", ptr, todo); |
| 180 | ptr += todo; |
| 181 | need_len -= todo; |
| 182 | } |
| 183 | |
Geert Uytterhoeven | c34924b | 2013-05-08 23:37:45 +0200 | [diff] [blame] | 184 | dev_dbg(ec_dev->dev, "loop done, ptr=%zd\n", ptr - ec_dev->din); |
Simon Glass | a17d94f | 2013-02-25 14:08:39 -0800 | [diff] [blame] | 185 | |
| 186 | return 0; |
| 187 | } |
| 188 | |
| 189 | /** |
| 190 | * cros_ec_command_spi_xfer - Transfer a message over SPI and receive the reply |
| 191 | * |
| 192 | * @ec_dev: ChromeOS EC device |
| 193 | * @ec_msg: Message to transfer |
| 194 | */ |
| 195 | static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev, |
| 196 | struct cros_ec_msg *ec_msg) |
| 197 | { |
| 198 | struct cros_ec_spi *ec_spi = ec_dev->priv; |
| 199 | struct spi_transfer trans; |
| 200 | struct spi_message msg; |
| 201 | int i, len; |
| 202 | u8 *ptr; |
| 203 | int sum; |
| 204 | int ret = 0, final_ret; |
| 205 | struct timespec ts; |
| 206 | |
| 207 | len = cros_ec_prepare_tx(ec_dev, ec_msg); |
| 208 | dev_dbg(ec_dev->dev, "prepared, len=%d\n", len); |
| 209 | |
| 210 | /* If it's too soon to do another transaction, wait */ |
| 211 | if (ec_spi->last_transfer_ns) { |
| 212 | struct timespec ts; |
| 213 | unsigned long delay; /* The delay completed so far */ |
| 214 | |
| 215 | ktime_get_ts(&ts); |
| 216 | delay = timespec_to_ns(&ts) - ec_spi->last_transfer_ns; |
| 217 | if (delay < EC_SPI_RECOVERY_TIME_NS) |
| 218 | ndelay(delay); |
| 219 | } |
| 220 | |
| 221 | /* Transmit phase - send our message */ |
| 222 | debug_packet(ec_dev->dev, "out", ec_dev->dout, len); |
| 223 | memset(&trans, '\0', sizeof(trans)); |
| 224 | trans.tx_buf = ec_dev->dout; |
| 225 | trans.len = len; |
| 226 | trans.cs_change = 1; |
| 227 | spi_message_init(&msg); |
| 228 | spi_message_add_tail(&trans, &msg); |
| 229 | ret = spi_sync(ec_spi->spi, &msg); |
| 230 | |
| 231 | /* Get the response */ |
| 232 | if (!ret) { |
| 233 | ret = cros_ec_spi_receive_response(ec_dev, |
| 234 | ec_msg->in_len + EC_MSG_TX_PROTO_BYTES); |
| 235 | } else { |
| 236 | dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret); |
| 237 | } |
| 238 | |
| 239 | /* turn off CS */ |
| 240 | spi_message_init(&msg); |
| 241 | final_ret = spi_sync(ec_spi->spi, &msg); |
| 242 | ktime_get_ts(&ts); |
| 243 | ec_spi->last_transfer_ns = timespec_to_ns(&ts); |
| 244 | if (!ret) |
| 245 | ret = final_ret; |
| 246 | if (ret < 0) { |
| 247 | dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret); |
| 248 | return ret; |
| 249 | } |
| 250 | |
| 251 | /* check response error code */ |
| 252 | ptr = ec_dev->din; |
| 253 | if (ptr[0]) { |
| 254 | dev_warn(ec_dev->dev, "command 0x%02x returned an error %d\n", |
| 255 | ec_msg->cmd, ptr[0]); |
| 256 | debug_packet(ec_dev->dev, "in_err", ptr, len); |
| 257 | return -EINVAL; |
| 258 | } |
| 259 | len = ptr[1]; |
| 260 | sum = ptr[0] + ptr[1]; |
| 261 | if (len > ec_msg->in_len) { |
| 262 | dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)", |
| 263 | len, ec_msg->in_len); |
| 264 | return -ENOSPC; |
| 265 | } |
| 266 | |
| 267 | /* copy response packet payload and compute checksum */ |
| 268 | for (i = 0; i < len; i++) { |
| 269 | sum += ptr[i + 2]; |
| 270 | if (ec_msg->in_len) |
| 271 | ec_msg->in_buf[i] = ptr[i + 2]; |
| 272 | } |
| 273 | sum &= 0xff; |
| 274 | |
| 275 | debug_packet(ec_dev->dev, "in", ptr, len + 3); |
| 276 | |
| 277 | if (sum != ptr[len + 2]) { |
| 278 | dev_err(ec_dev->dev, |
| 279 | "bad packet checksum, expected %02x, got %02x\n", |
| 280 | sum, ptr[len + 2]); |
| 281 | return -EBADMSG; |
| 282 | } |
| 283 | |
| 284 | return 0; |
| 285 | } |
| 286 | |
| 287 | static int cros_ec_probe_spi(struct spi_device *spi) |
| 288 | { |
| 289 | struct device *dev = &spi->dev; |
| 290 | struct cros_ec_device *ec_dev; |
| 291 | struct cros_ec_spi *ec_spi; |
| 292 | int err; |
| 293 | |
| 294 | spi->bits_per_word = 8; |
| 295 | spi->mode = SPI_MODE_0; |
| 296 | err = spi_setup(spi); |
| 297 | if (err < 0) |
| 298 | return err; |
| 299 | |
| 300 | ec_spi = devm_kzalloc(dev, sizeof(*ec_spi), GFP_KERNEL); |
| 301 | if (ec_spi == NULL) |
| 302 | return -ENOMEM; |
| 303 | ec_spi->spi = spi; |
| 304 | ec_dev = devm_kzalloc(dev, sizeof(*ec_dev), GFP_KERNEL); |
| 305 | if (!ec_dev) |
| 306 | return -ENOMEM; |
| 307 | |
| 308 | spi_set_drvdata(spi, ec_dev); |
| 309 | ec_dev->name = "SPI"; |
| 310 | ec_dev->dev = dev; |
| 311 | ec_dev->priv = ec_spi; |
| 312 | ec_dev->irq = spi->irq; |
| 313 | ec_dev->command_xfer = cros_ec_command_spi_xfer; |
| 314 | ec_dev->ec_name = ec_spi->spi->modalias; |
| 315 | ec_dev->phys_name = dev_name(&ec_spi->spi->dev); |
| 316 | ec_dev->parent = &ec_spi->spi->dev; |
| 317 | ec_dev->din_size = EC_MSG_BYTES + EC_MSG_PREAMBLE_COUNT; |
| 318 | ec_dev->dout_size = EC_MSG_BYTES; |
| 319 | |
| 320 | err = cros_ec_register(ec_dev); |
| 321 | if (err) { |
| 322 | dev_err(dev, "cannot register EC\n"); |
| 323 | return err; |
| 324 | } |
| 325 | |
| 326 | return 0; |
| 327 | } |
| 328 | |
| 329 | static int cros_ec_remove_spi(struct spi_device *spi) |
| 330 | { |
| 331 | struct cros_ec_device *ec_dev; |
| 332 | |
| 333 | ec_dev = spi_get_drvdata(spi); |
| 334 | cros_ec_remove(ec_dev); |
| 335 | |
| 336 | return 0; |
| 337 | } |
| 338 | |
| 339 | #ifdef CONFIG_PM_SLEEP |
| 340 | static int cros_ec_spi_suspend(struct device *dev) |
| 341 | { |
| 342 | struct cros_ec_device *ec_dev = dev_get_drvdata(dev); |
| 343 | |
| 344 | return cros_ec_suspend(ec_dev); |
| 345 | } |
| 346 | |
| 347 | static int cros_ec_spi_resume(struct device *dev) |
| 348 | { |
| 349 | struct cros_ec_device *ec_dev = dev_get_drvdata(dev); |
| 350 | |
| 351 | return cros_ec_resume(ec_dev); |
| 352 | } |
| 353 | #endif |
| 354 | |
| 355 | static SIMPLE_DEV_PM_OPS(cros_ec_spi_pm_ops, cros_ec_spi_suspend, |
| 356 | cros_ec_spi_resume); |
| 357 | |
| 358 | static const struct spi_device_id cros_ec_spi_id[] = { |
| 359 | { "cros-ec-spi", 0 }, |
| 360 | { } |
| 361 | }; |
| 362 | MODULE_DEVICE_TABLE(spi, cros_ec_spi_id); |
| 363 | |
| 364 | static struct spi_driver cros_ec_driver_spi = { |
| 365 | .driver = { |
| 366 | .name = "cros-ec-spi", |
| 367 | .owner = THIS_MODULE, |
| 368 | .pm = &cros_ec_spi_pm_ops, |
| 369 | }, |
| 370 | .probe = cros_ec_probe_spi, |
| 371 | .remove = cros_ec_remove_spi, |
| 372 | .id_table = cros_ec_spi_id, |
| 373 | }; |
| 374 | |
| 375 | module_spi_driver(cros_ec_driver_spi); |
| 376 | |
| 377 | MODULE_LICENSE("GPL"); |
| 378 | MODULE_DESCRIPTION("ChromeOS EC multi function device (SPI)"); |