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