drivers/platform/chrome/cros_ec_spi.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 // SPI interface for ChromeOS Embedded Controller
   3 //
   4 // Copyright (C) 2012 Google, Inc
   5
   6 #include <linux/delay.h>
   7 #include <linux/kernel.h>
   8 #include <linux/module.h>
   9 #include <linux/of.h>
  10 #include <linux/platform_data/cros_ec_commands.h>
  11 #include <linux/platform_data/cros_ec_proto.h>
  12 #include <linux/platform_device.h>
  13 #include <linux/slab.h>
  14 #include <linux/spi/spi.h>
  15 #include <uapi/linux/sched/types.h>
  16
  17 #include "cros_ec.h"
  18
  19 /* The header byte, which follows the preamble */
  20 #define EC_MSG_HEADER                   0xec
  21
  22 /*
  23  * Number of EC preamble bytes we read at a time. Since it takes
  24  * about 400-500us for the EC to respond there is not a lot of
  25  * point in tuning this. If the EC could respond faster then
  26  * we could increase this so that might expect the preamble and
  27  * message to occur in a single transaction. However, the maximum
  28  * SPI transfer size is 256 bytes, so at 5MHz we need a response
  29  * time of perhaps <320us (200 bytes / 1600 bits).
  30  */
  31 #define EC_MSG_PREAMBLE_COUNT           32
  32
  33 /*
  34  * Allow for a long time for the EC to respond.  We support i2c
  35  * tunneling and support fairly long messages for the tunnel (249
  36  * bytes long at the moment).  If we're talking to a 100 kHz device
  37  * on the other end and need to transfer ~256 bytes, then we need:
  38  *  10 us/bit * ~10 bits/byte * ~256 bytes = ~25ms
  39  *
  40  * We'll wait 8 times that to handle clock stretching and other
  41  * paranoia.  Note that some battery gas gauge ICs claim to have a
  42  * clock stretch of 144ms in rare situations.  That's incentive for
  43  * not directly passing i2c through, but it's too late for that for
  44  * existing hardware.
  45  *
  46  * It's pretty unlikely that we'll really see a 249 byte tunnel in
  47  * anything other than testing.  If this was more common we might
  48  * consider having slow commands like this require a GET_STATUS
  49  * wait loop.  The 'flash write' command would be another candidate
  50  * for this, clocking in at 2-3ms.
  51  */
  52 #define EC_MSG_DEADLINE_MS              200
  53
  54 /*
  55   * Time between raising the SPI chip select (for the end of a
  56   * transaction) and dropping it again (for the next transaction).
  57   * If we go too fast, the EC will miss the transaction. We know that we
  58   * need at least 70 us with the 16 MHz STM32 EC, so go with 200 us to be
  59   * safe.
  60   */
  61 #define EC_SPI_RECOVERY_TIME_NS (200 * 1000)
  62
  63 /**
  64  * struct cros_ec_spi - information about a SPI-connected EC
  65  *
  66  * @spi: SPI device we are connected to
  67  * @last_transfer_ns: time that we last finished a transfer.
  68  * @start_of_msg_delay: used to set the delay_usecs on the spi_transfer that
  69  *      is sent when we want to turn on CS at the start of a transaction.
  70  * @end_of_msg_delay: used to set the delay_usecs on the spi_transfer that
  71  *      is sent when we want to turn off CS at the end of a transaction.
  72  * @high_pri_worker: Used to schedule high priority work.
  73  */
  74 struct cros_ec_spi {
  75         struct spi_device *spi;
  76         s64 last_transfer_ns;
  77         unsigned int start_of_msg_delay;
  78         unsigned int end_of_msg_delay;
  79         struct kthread_worker *high_pri_worker;
  80 };
  81
  82 typedef int (*cros_ec_xfer_fn_t) (struct cros_ec_device *ec_dev,
  83                                   struct cros_ec_command *ec_msg);
  84
  85 /**
  86  * struct cros_ec_xfer_work_params - params for our high priority workers
  87  *
  88  * @work: The work_struct needed to queue work
  89  * @fn: The function to use to transfer
  90  * @ec_dev: ChromeOS EC device
  91  * @ec_msg: Message to transfer
  92  * @ret: The return value of the function
  93  */
  94
  95 struct cros_ec_xfer_work_params {
  96         struct kthread_work work;
  97         cros_ec_xfer_fn_t fn;
  98         struct cros_ec_device *ec_dev;
  99         struct cros_ec_command *ec_msg;
 100         int ret;
 101 };
 102
 103 static void debug_packet(struct device *dev, const char *name, u8 *ptr,
 104                          int len)
 105 {
 106 #ifdef DEBUG
 107         int i;
 108
 109         dev_dbg(dev, "%s: ", name);
 110         for (i = 0; i < len; i++)
 111                 pr_cont(" %02x", ptr[i]);
 112
 113         pr_cont("\n");
 114 #endif
 115 }
 116
 117 static int terminate_request(struct cros_ec_device *ec_dev)
 118 {
 119         struct cros_ec_spi *ec_spi = ec_dev->priv;
 120         struct spi_message msg;
 121         struct spi_transfer trans;
 122         int ret;
 123
 124         /*
 125          * Turn off CS, possibly adding a delay to ensure the rising edge
 126          * doesn't come too soon after the end of the data.
 127          */
 128         spi_message_init(&msg);
 129         memset(&trans, 0, sizeof(trans));
 130         trans.delay_usecs = ec_spi->end_of_msg_delay;
 131         spi_message_add_tail(&trans, &msg);
 132
 133         ret = spi_sync_locked(ec_spi->spi, &msg);
 134
 135         /* Reset end-of-response timer */
 136         ec_spi->last_transfer_ns = ktime_get_ns();
 137         if (ret < 0) {
 138                 dev_err(ec_dev->dev,
 139                         "cs-deassert spi transfer failed: %d\n",
 140                         ret);
 141         }
 142
 143         return ret;
 144 }
 145
 146 /**
 147  * receive_n_bytes - receive n bytes from the EC.
 148  *
 149  * Assumes buf is a pointer into the ec_dev->din buffer
 150  */
 151 static int receive_n_bytes(struct cros_ec_device *ec_dev, u8 *buf, int n)
 152 {
 153         struct cros_ec_spi *ec_spi = ec_dev->priv;
 154         struct spi_transfer trans;
 155         struct spi_message msg;
 156         int ret;
 157
 158         BUG_ON(buf - ec_dev->din + n > ec_dev->din_size);
 159
 160         memset(&trans, 0, sizeof(trans));
 161         trans.cs_change = 1;
 162         trans.rx_buf = buf;
 163         trans.len = n;
 164
 165         spi_message_init(&msg);
 166         spi_message_add_tail(&trans, &msg);
 167         ret = spi_sync_locked(ec_spi->spi, &msg);
 168         if (ret < 0)
 169                 dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
 170
 171         return ret;
 172 }
 173
 174 /**
 175  * cros_ec_spi_receive_packet - Receive a packet from the EC.
 176  *
 177  * This function has two phases: reading the preamble bytes (since if we read
 178  * data from the EC before it is ready to send, we just get preamble) and
 179  * reading the actual message.
 180  *
 181  * The received data is placed into ec_dev->din.
 182  *
 183  * @ec_dev: ChromeOS EC device
 184  * @need_len: Number of message bytes we need to read
 185  */
 186 static int cros_ec_spi_receive_packet(struct cros_ec_device *ec_dev,
 187                                       int need_len)
 188 {
 189         struct ec_host_response *response;
 190         u8 *ptr, *end;
 191         int ret;
 192         unsigned long deadline;
 193         int todo;
 194
 195         BUG_ON(ec_dev->din_size < EC_MSG_PREAMBLE_COUNT);
 196
 197         /* Receive data until we see the header byte */
 198         deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS);
 199         while (true) {
 200                 unsigned long start_jiffies = jiffies;
 201
 202                 ret = receive_n_bytes(ec_dev,
 203                                       ec_dev->din,
 204                                       EC_MSG_PREAMBLE_COUNT);
 205                 if (ret < 0)
 206                         return ret;
 207
 208                 ptr = ec_dev->din;
 209                 for (end = ptr + EC_MSG_PREAMBLE_COUNT; ptr != end; ptr++) {
 210                         if (*ptr == EC_SPI_FRAME_START) {
 211                                 dev_dbg(ec_dev->dev, "msg found at %zd\n",
 212                                         ptr - ec_dev->din);
 213                                 break;
 214                         }
 215                 }
 216                 if (ptr != end)
 217                         break;
 218
 219                 /*
 220                  * Use the time at the start of the loop as a timeout.  This
 221                  * gives us one last shot at getting the transfer and is useful
 222                  * in case we got context switched out for a while.
 223                  */
 224                 if (time_after(start_jiffies, deadline)) {
 225                         dev_warn(ec_dev->dev, "EC failed to respond in time\n");
 226                         return -ETIMEDOUT;
 227                 }
 228         }
 229
 230         /*
 231          * ptr now points to the header byte. Copy any valid data to the
 232          * start of our buffer
 233          */
 234         todo = end - ++ptr;
 235         BUG_ON(todo < 0 || todo > ec_dev->din_size);
 236         todo = min(todo, need_len);
 237         memmove(ec_dev->din, ptr, todo);
 238         ptr = ec_dev->din + todo;
 239         dev_dbg(ec_dev->dev, "need %d, got %d bytes from preamble\n",
 240                 need_len, todo);
 241         need_len -= todo;
 242
 243         /* If the entire response struct wasn't read, get the rest of it. */
 244         if (todo < sizeof(*response)) {
 245                 ret = receive_n_bytes(ec_dev, ptr, sizeof(*response) - todo);
 246                 if (ret < 0)
 247                         return -EBADMSG;
 248                 ptr += (sizeof(*response) - todo);
 249                 todo = sizeof(*response);
 250         }
 251
 252         response = (struct ec_host_response *)ec_dev->din;
 253
 254         /* Abort if data_len is too large. */
 255         if (response->data_len > ec_dev->din_size)
 256                 return -EMSGSIZE;
 257
 258         /* Receive data until we have it all */
 259         while (need_len > 0) {
 260                 /*
 261                  * We can't support transfers larger than the SPI FIFO size
 262                  * unless we have DMA. We don't have DMA on the ISP SPI ports
 263                  * for Exynos. We need a way of asking SPI driver for
 264                  * maximum-supported transfer size.
 265                  */
 266                 todo = min(need_len, 256);
 267                 dev_dbg(ec_dev->dev, "loop, todo=%d, need_len=%d, ptr=%zd\n",
 268                         todo, need_len, ptr - ec_dev->din);
 269
 270                 ret = receive_n_bytes(ec_dev, ptr, todo);
 271                 if (ret < 0)
 272                         return ret;
 273
 274                 ptr += todo;
 275                 need_len -= todo;
 276         }
 277
 278         dev_dbg(ec_dev->dev, "loop done, ptr=%zd\n", ptr - ec_dev->din);
 279
 280         return 0;
 281 }
 282
 283 /**
 284  * cros_ec_spi_receive_response - Receive a response from the EC.
 285  *
 286  * This function has two phases: reading the preamble bytes (since if we read
 287  * data from the EC before it is ready to send, we just get preamble) and
 288  * reading the actual message.
 289  *
 290  * The received data is placed into ec_dev->din.
 291  *
 292  * @ec_dev: ChromeOS EC device
 293  * @need_len: Number of message bytes we need to read
 294  */
 295 static int cros_ec_spi_receive_response(struct cros_ec_device *ec_dev,
 296                                         int need_len)
 297 {
 298         u8 *ptr, *end;
 299         int ret;
 300         unsigned long deadline;
 301         int todo;
 302
 303         BUG_ON(ec_dev->din_size < EC_MSG_PREAMBLE_COUNT);
 304
 305         /* Receive data until we see the header byte */
 306         deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS);
 307         while (true) {
 308                 unsigned long start_jiffies = jiffies;
 309
 310                 ret = receive_n_bytes(ec_dev,
 311                                       ec_dev->din,
 312                                       EC_MSG_PREAMBLE_COUNT);
 313                 if (ret < 0)
 314                         return ret;
 315
 316                 ptr = ec_dev->din;
 317                 for (end = ptr + EC_MSG_PREAMBLE_COUNT; ptr != end; ptr++) {
 318                         if (*ptr == EC_SPI_FRAME_START) {
 319                                 dev_dbg(ec_dev->dev, "msg found at %zd\n",
 320                                         ptr - ec_dev->din);
 321                                 break;
 322                         }
 323                 }
 324                 if (ptr != end)
 325                         break;
 326
 327                 /*
 328                  * Use the time at the start of the loop as a timeout.  This
 329                  * gives us one last shot at getting the transfer and is useful
 330                  * in case we got context switched out for a while.
 331                  */
 332                 if (time_after(start_jiffies, deadline)) {
 333                         dev_warn(ec_dev->dev, "EC failed to respond in time\n");
 334                         return -ETIMEDOUT;
 335                 }
 336         }
 337
 338         /*
 339          * ptr now points to the header byte. Copy any valid data to the
 340          * start of our buffer
 341          */
 342         todo = end - ++ptr;
 343         BUG_ON(todo < 0 || todo > ec_dev->din_size);
 344         todo = min(todo, need_len);
 345         memmove(ec_dev->din, ptr, todo);
 346         ptr = ec_dev->din + todo;
 347         dev_dbg(ec_dev->dev, "need %d, got %d bytes from preamble\n",
 348                  need_len, todo);
 349         need_len -= todo;
 350
 351         /* Receive data until we have it all */
 352         while (need_len > 0) {
 353                 /*
 354                  * We can't support transfers larger than the SPI FIFO size
 355                  * unless we have DMA. We don't have DMA on the ISP SPI ports
 356                  * for Exynos. We need a way of asking SPI driver for
 357                  * maximum-supported transfer size.
 358                  */
 359                 todo = min(need_len, 256);
 360                 dev_dbg(ec_dev->dev, "loop, todo=%d, need_len=%d, ptr=%zd\n",
 361                         todo, need_len, ptr - ec_dev->din);
 362
 363                 ret = receive_n_bytes(ec_dev, ptr, todo);
 364                 if (ret < 0)
 365                         return ret;
 366
 367                 debug_packet(ec_dev->dev, "interim", ptr, todo);
 368                 ptr += todo;
 369                 need_len -= todo;
 370         }
 371
 372         dev_dbg(ec_dev->dev, "loop done, ptr=%zd\n", ptr - ec_dev->din);
 373
 374         return 0;
 375 }
 376
 377 /**
 378  * do_cros_ec_pkt_xfer_spi - Transfer a packet over SPI and receive the reply
 379  *
 380  * @ec_dev: ChromeOS EC device
 381  * @ec_msg: Message to transfer
 382  */
 383 static int do_cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
 384                                    struct cros_ec_command *ec_msg)
 385 {
 386         struct ec_host_response *response;
 387         struct cros_ec_spi *ec_spi = ec_dev->priv;
 388         struct spi_transfer trans, trans_delay;
 389         struct spi_message msg;
 390         int i, len;
 391         u8 *ptr;
 392         u8 *rx_buf;
 393         u8 sum;
 394         u8 rx_byte;
 395         int ret = 0, final_ret;
 396         unsigned long delay;
 397
 398         len = cros_ec_prepare_tx(ec_dev, ec_msg);
 399         dev_dbg(ec_dev->dev, "prepared, len=%d\n", len);
 400
 401         /* If it's too soon to do another transaction, wait */
 402         delay = ktime_get_ns() - ec_spi->last_transfer_ns;
 403         if (delay < EC_SPI_RECOVERY_TIME_NS)
 404                 ndelay(EC_SPI_RECOVERY_TIME_NS - delay);
 405
 406         rx_buf = kzalloc(len, GFP_KERNEL);
 407         if (!rx_buf)
 408                 return -ENOMEM;
 409
 410         spi_bus_lock(ec_spi->spi->master);
 411
 412         /*
 413          * Leave a gap between CS assertion and clocking of data to allow the
 414          * EC time to wakeup.
 415          */
 416         spi_message_init(&msg);
 417         if (ec_spi->start_of_msg_delay) {
 418                 memset(&trans_delay, 0, sizeof(trans_delay));
 419                 trans_delay.delay_usecs = ec_spi->start_of_msg_delay;
 420                 spi_message_add_tail(&trans_delay, &msg);
 421         }
 422
 423         /* Transmit phase - send our message */
 424         memset(&trans, 0, sizeof(trans));
 425         trans.tx_buf = ec_dev->dout;
 426         trans.rx_buf = rx_buf;
 427         trans.len = len;
 428         trans.cs_change = 1;
 429         spi_message_add_tail(&trans, &msg);
 430         ret = spi_sync_locked(ec_spi->spi, &msg);
 431
 432         /* Get the response */
 433         if (!ret) {
 434                 /* Verify that EC can process command */
 435                 for (i = 0; i < len; i++) {
 436                         rx_byte = rx_buf[i];
 437                         /*
 438                          * Seeing the PAST_END, RX_BAD_DATA, or NOT_READY
 439                          * markers are all signs that the EC didn't fully
 440                          * receive our command. e.g., if the EC is flashing
 441                          * itself, it can't respond to any commands and instead
 442                          * clocks out EC_SPI_PAST_END from its SPI hardware
 443                          * buffer. Similar occurrences can happen if the AP is
 444                          * too slow to clock out data after asserting CS -- the
 445                          * EC will abort and fill its buffer with
 446                          * EC_SPI_RX_BAD_DATA.
 447                          *
 448                          * In all cases, these errors should be safe to retry.
 449                          * Report -EAGAIN and let the caller decide what to do
 450                          * about that.
 451                          */
 452                         if (rx_byte == EC_SPI_PAST_END  ||
 453                             rx_byte == EC_SPI_RX_BAD_DATA ||
 454                             rx_byte == EC_SPI_NOT_READY) {
 455                                 ret = -EAGAIN;
 456                                 break;
 457                         }
 458                 }
 459         }
 460
 461         if (!ret)
 462                 ret = cros_ec_spi_receive_packet(ec_dev,
 463                                 ec_msg->insize + sizeof(*response));
 464         else if (ret != -EAGAIN)
 465                 dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
 466
 467         final_ret = terminate_request(ec_dev);
 468
 469         spi_bus_unlock(ec_spi->spi->master);
 470
 471         if (!ret)
 472                 ret = final_ret;
 473         if (ret < 0)
 474                 goto exit;
 475
 476         ptr = ec_dev->din;
 477
 478         /* check response error code */
 479         response = (struct ec_host_response *)ptr;
 480         ec_msg->result = response->result;
 481
 482         ret = cros_ec_check_result(ec_dev, ec_msg);
 483         if (ret)
 484                 goto exit;
 485
 486         len = response->data_len;
 487         sum = 0;
 488         if (len > ec_msg->insize) {
 489                 dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)",
 490                         len, ec_msg->insize);
 491                 ret = -EMSGSIZE;
 492                 goto exit;
 493         }
 494
 495         for (i = 0; i < sizeof(*response); i++)
 496                 sum += ptr[i];
 497
 498         /* copy response packet payload and compute checksum */
 499         memcpy(ec_msg->data, ptr + sizeof(*response), len);
 500         for (i = 0; i < len; i++)
 501                 sum += ec_msg->data[i];
 502
 503         if (sum) {
 504                 dev_err(ec_dev->dev,
 505                         "bad packet checksum, calculated %x\n",
 506                         sum);
 507                 ret = -EBADMSG;
 508                 goto exit;
 509         }
 510
 511         ret = len;
 512 exit:
 513         kfree(rx_buf);
 514         if (ec_msg->command == EC_CMD_REBOOT_EC)
 515                 msleep(EC_REBOOT_DELAY_MS);
 516
 517         return ret;
 518 }
 519
 520 /**
 521  * do_cros_ec_cmd_xfer_spi - Transfer a message over SPI and receive the reply
 522  *
 523  * @ec_dev: ChromeOS EC device
 524  * @ec_msg: Message to transfer
 525  */
 526 static int do_cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
 527                                    struct cros_ec_command *ec_msg)
 528 {
 529         struct cros_ec_spi *ec_spi = ec_dev->priv;
 530         struct spi_transfer trans;
 531         struct spi_message msg;
 532         int i, len;
 533         u8 *ptr;
 534         u8 *rx_buf;
 535         u8 rx_byte;
 536         int sum;
 537         int ret = 0, final_ret;
 538         unsigned long delay;
 539
 540         len = cros_ec_prepare_tx(ec_dev, ec_msg);
 541         dev_dbg(ec_dev->dev, "prepared, len=%d\n", len);
 542
 543         /* If it's too soon to do another transaction, wait */
 544         delay = ktime_get_ns() - ec_spi->last_transfer_ns;
 545         if (delay < EC_SPI_RECOVERY_TIME_NS)
 546                 ndelay(EC_SPI_RECOVERY_TIME_NS - delay);
 547
 548         rx_buf = kzalloc(len, GFP_KERNEL);
 549         if (!rx_buf)
 550                 return -ENOMEM;
 551
 552         spi_bus_lock(ec_spi->spi->master);
 553
 554         /* Transmit phase - send our message */
 555         debug_packet(ec_dev->dev, "out", ec_dev->dout, len);
 556         memset(&trans, 0, sizeof(trans));
 557         trans.tx_buf = ec_dev->dout;
 558         trans.rx_buf = rx_buf;
 559         trans.len = len;
 560         trans.cs_change = 1;
 561         spi_message_init(&msg);
 562         spi_message_add_tail(&trans, &msg);
 563         ret = spi_sync_locked(ec_spi->spi, &msg);
 564
 565         /* Get the response */
 566         if (!ret) {
 567                 /* Verify that EC can process command */
 568                 for (i = 0; i < len; i++) {
 569                         rx_byte = rx_buf[i];
 570                         /* See comments in cros_ec_pkt_xfer_spi() */
 571                         if (rx_byte == EC_SPI_PAST_END  ||
 572                             rx_byte == EC_SPI_RX_BAD_DATA ||
 573                             rx_byte == EC_SPI_NOT_READY) {
 574                                 ret = -EAGAIN;
 575                                 break;
 576                         }
 577                 }
 578         }
 579
 580         if (!ret)
 581                 ret = cros_ec_spi_receive_response(ec_dev,
 582                                 ec_msg->insize + EC_MSG_TX_PROTO_BYTES);
 583         else if (ret != -EAGAIN)
 584                 dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
 585
 586         final_ret = terminate_request(ec_dev);
 587
 588         spi_bus_unlock(ec_spi->spi->master);
 589
 590         if (!ret)
 591                 ret = final_ret;
 592         if (ret < 0)
 593                 goto exit;
 594
 595         ptr = ec_dev->din;
 596
 597         /* check response error code */
 598         ec_msg->result = ptr[0];
 599         ret = cros_ec_check_result(ec_dev, ec_msg);
 600         if (ret)
 601                 goto exit;
 602
 603         len = ptr[1];
 604         sum = ptr[0] + ptr[1];
 605         if (len > ec_msg->insize) {
 606                 dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)",
 607                         len, ec_msg->insize);
 608                 ret = -ENOSPC;
 609                 goto exit;
 610         }
 611
 612         /* copy response packet payload and compute checksum */
 613         for (i = 0; i < len; i++) {
 614                 sum += ptr[i + 2];
 615                 if (ec_msg->insize)
 616                         ec_msg->data[i] = ptr[i + 2];
 617         }
 618         sum &= 0xff;
 619
 620         debug_packet(ec_dev->dev, "in", ptr, len + 3);
 621
 622         if (sum != ptr[len + 2]) {
 623                 dev_err(ec_dev->dev,
 624                         "bad packet checksum, expected %02x, got %02x\n",
 625                         sum, ptr[len + 2]);
 626                 ret = -EBADMSG;
 627                 goto exit;
 628         }
 629
 630         ret = len;
 631 exit:
 632         kfree(rx_buf);
 633         if (ec_msg->command == EC_CMD_REBOOT_EC)
 634                 msleep(EC_REBOOT_DELAY_MS);
 635
 636         return ret;
 637 }
 638
 639 static void cros_ec_xfer_high_pri_work(struct kthread_work *work)
 640 {
 641         struct cros_ec_xfer_work_params *params;
 642
 643         params = container_of(work, struct cros_ec_xfer_work_params, work);
 644         params->ret = params->fn(params->ec_dev, params->ec_msg);
 645 }
 646
 647 static int cros_ec_xfer_high_pri(struct cros_ec_device *ec_dev,
 648                                  struct cros_ec_command *ec_msg,
 649                                  cros_ec_xfer_fn_t fn)
 650 {
 651         struct cros_ec_spi *ec_spi = ec_dev->priv;
 652         struct cros_ec_xfer_work_params params = {
 653                 .work = KTHREAD_WORK_INIT(params.work,
 654                                           cros_ec_xfer_high_pri_work),
 655                 .ec_dev = ec_dev,
 656                 .ec_msg = ec_msg,
 657                 .fn = fn,
 658         };
 659
 660         /*
 661          * This looks a bit ridiculous.  Why do the work on a
 662          * different thread if we're just going to block waiting for
 663          * the thread to finish?  The key here is that the thread is
 664          * running at high priority but the calling context might not
 665          * be.  We need to be at high priority to avoid getting
 666          * context switched out for too long and the EC giving up on
 667          * the transfer.
 668          */
 669         kthread_queue_work(ec_spi->high_pri_worker, &params.work);
 670         kthread_flush_work(&params.work);
 671
 672         return params.ret;
 673 }
 674
 675 static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
 676                                 struct cros_ec_command *ec_msg)
 677 {
 678         return cros_ec_xfer_high_pri(ec_dev, ec_msg, do_cros_ec_pkt_xfer_spi);
 679 }
 680
 681 static int cros_ec_cmd_xfer_spi(struct cros_ec_device *ec_dev,
 682                                 struct cros_ec_command *ec_msg)
 683 {
 684         return cros_ec_xfer_high_pri(ec_dev, ec_msg, do_cros_ec_cmd_xfer_spi);
 685 }
 686
 687 static void cros_ec_spi_dt_probe(struct cros_ec_spi *ec_spi, struct device *dev)
 688 {
 689         struct device_node *np = dev->of_node;
 690         u32 val;
 691         int ret;
 692
 693         ret = of_property_read_u32(np, "google,cros-ec-spi-pre-delay", &val);
 694         if (!ret)
 695                 ec_spi->start_of_msg_delay = val;
 696
 697         ret = of_property_read_u32(np, "google,cros-ec-spi-msg-delay", &val);
 698         if (!ret)
 699                 ec_spi->end_of_msg_delay = val;
 700 }
 701
 702 static void cros_ec_spi_high_pri_release(void *worker)
 703 {
 704         kthread_destroy_worker(worker);
 705 }
 706
 707 static int cros_ec_spi_devm_high_pri_alloc(struct device *dev,
 708                                            struct cros_ec_spi *ec_spi)
 709 {
 710         struct sched_param sched_priority = {
 711                 .sched_priority = MAX_RT_PRIO / 2,
 712         };
 713         int err;
 714
 715         ec_spi->high_pri_worker =
 716                 kthread_create_worker(0, "cros_ec_spi_high_pri");
 717
 718         if (IS_ERR(ec_spi->high_pri_worker)) {
 719                 err = PTR_ERR(ec_spi->high_pri_worker);
 720                 dev_err(dev, "Can't create cros_ec high pri worker: %d\n", err);
 721                 return err;
 722         }
 723
 724         err = devm_add_action_or_reset(dev, cros_ec_spi_high_pri_release,
 725                                        ec_spi->high_pri_worker);
 726         if (err)
 727                 return err;
 728
 729         err = sched_setscheduler_nocheck(ec_spi->high_pri_worker->task,
 730                                          SCHED_FIFO, &sched_priority);
 731         if (err)
 732                 dev_err(dev, "Can't set cros_ec high pri priority: %d\n", err);
 733         return err;
 734 }
 735
 736 static int cros_ec_spi_probe(struct spi_device *spi)
 737 {
 738         struct device *dev = &spi->dev;
 739         struct cros_ec_device *ec_dev;
 740         struct cros_ec_spi *ec_spi;
 741         int err;
 742
 743         spi->bits_per_word = 8;
 744         spi->mode = SPI_MODE_0;
 745         spi->rt = true;
 746         err = spi_setup(spi);
 747         if (err < 0)
 748                 return err;
 749
 750         ec_spi = devm_kzalloc(dev, sizeof(*ec_spi), GFP_KERNEL);
 751         if (ec_spi == NULL)
 752                 return -ENOMEM;
 753         ec_spi->spi = spi;
 754         ec_dev = devm_kzalloc(dev, sizeof(*ec_dev), GFP_KERNEL);
 755         if (!ec_dev)
 756                 return -ENOMEM;
 757
 758         /* Check for any DT properties */
 759         cros_ec_spi_dt_probe(ec_spi, dev);
 760
 761         spi_set_drvdata(spi, ec_dev);
 762         ec_dev->dev = dev;
 763         ec_dev->priv = ec_spi;
 764         ec_dev->irq = spi->irq;
 765         ec_dev->cmd_xfer = cros_ec_cmd_xfer_spi;
 766         ec_dev->pkt_xfer = cros_ec_pkt_xfer_spi;
 767         ec_dev->phys_name = dev_name(&ec_spi->spi->dev);
 768         ec_dev->din_size = EC_MSG_PREAMBLE_COUNT +
 769                            sizeof(struct ec_host_response) +
 770                            sizeof(struct ec_response_get_protocol_info);
 771         ec_dev->dout_size = sizeof(struct ec_host_request);
 772
 773         ec_spi->last_transfer_ns = ktime_get_ns();
 774
 775         err = cros_ec_spi_devm_high_pri_alloc(dev, ec_spi);
 776         if (err)
 777                 return err;
 778
 779         err = cros_ec_register(ec_dev);
 780         if (err) {
 781                 dev_err(dev, "cannot register EC\n");
 782                 return err;
 783         }
 784
 785         device_init_wakeup(&spi->dev, true);
 786
 787         return 0;
 788 }
 789
 790 static int cros_ec_spi_remove(struct spi_device *spi)
 791 {
 792         struct cros_ec_device *ec_dev = spi_get_drvdata(spi);
 793
 794         return cros_ec_unregister(ec_dev);
 795 }
 796
 797 #ifdef CONFIG_PM_SLEEP
 798 static int cros_ec_spi_suspend(struct device *dev)
 799 {
 800         struct cros_ec_device *ec_dev = dev_get_drvdata(dev);
 801
 802         return cros_ec_suspend(ec_dev);
 803 }
 804
 805 static int cros_ec_spi_resume(struct device *dev)
 806 {
 807         struct cros_ec_device *ec_dev = dev_get_drvdata(dev);
 808
 809         return cros_ec_resume(ec_dev);
 810 }
 811 #endif
 812
 813 static SIMPLE_DEV_PM_OPS(cros_ec_spi_pm_ops, cros_ec_spi_suspend,
 814                          cros_ec_spi_resume);
 815
 816 static const struct of_device_id cros_ec_spi_of_match[] = {
 817         { .compatible = "google,cros-ec-spi", },
 818         { /* sentinel */ },
 819 };
 820 MODULE_DEVICE_TABLE(of, cros_ec_spi_of_match);
 821
 822 static const struct spi_device_id cros_ec_spi_id[] = {
 823         { "cros-ec-spi", 0 },
 824         { }
 825 };
 826 MODULE_DEVICE_TABLE(spi, cros_ec_spi_id);
 827
 828 static struct spi_driver cros_ec_driver_spi = {
 829         .driver = {
 830                 .name   = "cros-ec-spi",
 831                 .of_match_table = cros_ec_spi_of_match,
 832                 .pm     = &cros_ec_spi_pm_ops,
 833         },
 834         .probe          = cros_ec_spi_probe,
 835         .remove         = cros_ec_spi_remove,
 836         .id_table       = cros_ec_spi_id,
 837 };
 838
 839 module_spi_driver(cros_ec_driver_spi);
 840
 841 MODULE_LICENSE("GPL v2");
 842 MODULE_DESCRIPTION("SPI interface for ChromeOS Embedded Controller");