drivers/mfd/cros_ec_spi.c

   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/of.h>
  22 #include <linux/platform_device.h>
  23 #include <linux/slab.h>
  24 #include <linux/spi/spi.h>
  25
  26
  27 /* The header byte, which follows the preamble */
  28 #define EC_MSG_HEADER                   0xec
  29
  30 /*
  31  * Number of EC preamble bytes we read at a time. Since it takes
  32  * about 400-500us for the EC to respond there is not a lot of
  33  * point in tuning this. If the EC could respond faster then
  34  * we could increase this so that might expect the preamble and
  35  * message to occur in a single transaction. However, the maximum
  36  * SPI transfer size is 256 bytes, so at 5MHz we need a response
  37  * time of perhaps <320us (200 bytes / 1600 bits).
  38  */
  39 #define EC_MSG_PREAMBLE_COUNT           32
  40
  41 /*
  42   * We must get a response from the EC in 5ms. This is a very long
  43   * time, but the flash write command can take 2-3ms. The EC command
  44   * processing is currently not very fast (about 500us). We could
  45   * look at speeding this up and making the flash write command a
  46   * 'slow' command, requiring a GET_STATUS wait loop, like flash
  47   * erase.
  48   */
  49 #define EC_MSG_DEADLINE_MS              5
  50
  51 /*
  52   * Time between raising the SPI chip select (for the end of a
  53   * transaction) and dropping it again (for the next transaction).
  54   * If we go too fast, the EC will miss the transaction. We know that we
  55   * need at least 70 us with the 16 MHz STM32 EC, so go with 200 us to be
  56   * safe.
  57   */
  58 #define EC_SPI_RECOVERY_TIME_NS (200 * 1000)
  59
  60 /**
  61  * struct cros_ec_spi - information about a SPI-connected EC
  62  *
  63  * @spi: SPI device we are connected to
  64  * @last_transfer_ns: time that we last finished a transfer, or 0 if there
  65  *      if no record
  66  * @end_of_msg_delay: used to set the delay_usecs on the spi_transfer that
  67  *      is sent when we want to turn off CS at the end of a transaction.
  68  */
  69 struct cros_ec_spi {
  70         struct spi_device *spi;
  71         s64 last_transfer_ns;
  72         unsigned int end_of_msg_delay;
  73 };
  74
  75 static void debug_packet(struct device *dev, const char *name, u8 *ptr,
  76                           int len)
  77 {
  78 #ifdef DEBUG
  79         int i;
  80
  81         dev_dbg(dev, "%s: ", name);
  82         for (i = 0; i < len; i++)
  83                 pr_cont(" %02x", ptr[i]);
  84
  85         pr_cont("\n");
  86 #endif
  87 }
  88
  89 /**
  90  * cros_ec_spi_receive_response - Receive a response from the EC.
  91  *
  92  * This function has two phases: reading the preamble bytes (since if we read
  93  * data from the EC before it is ready to send, we just get preamble) and
  94  * reading the actual message.
  95  *
  96  * The received data is placed into ec_dev->din.
  97  *
  98  * @ec_dev: ChromeOS EC device
  99  * @need_len: Number of message bytes we need to read
 100  */
 101 static int cros_ec_spi_receive_response(struct cros_ec_device *ec_dev,
 102                                         int need_len)
 103 {
 104         struct cros_ec_spi *ec_spi = ec_dev->priv;
 105         struct spi_transfer trans;
 106         struct spi_message msg;
 107         u8 *ptr, *end;
 108         int ret;
 109         unsigned long deadline;
 110         int todo;
 111
 112         /* Receive data until we see the header byte */
 113         deadline = jiffies + msecs_to_jiffies(EC_MSG_DEADLINE_MS);
 114         do {
 115                 memset(&trans, 0, sizeof(trans));
 116                 trans.cs_change = 1;
 117                 trans.rx_buf = ptr = ec_dev->din;
 118                 trans.len = EC_MSG_PREAMBLE_COUNT;
 119
 120                 spi_message_init(&msg);
 121                 spi_message_add_tail(&trans, &msg);
 122                 ret = spi_sync(ec_spi->spi, &msg);
 123                 if (ret < 0) {
 124                         dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
 125                         return ret;
 126                 }
 127
 128                 for (end = ptr + EC_MSG_PREAMBLE_COUNT; ptr != end; ptr++) {
 129                         if (*ptr == EC_MSG_HEADER) {
 130                                 dev_dbg(ec_dev->dev, "msg found at %zd\n",
 131                                         ptr - ec_dev->din);
 132                                 break;
 133                         }
 134                 }
 135
 136                 if (time_after(jiffies, deadline)) {
 137                         dev_warn(ec_dev->dev, "EC failed to respond in time\n");
 138                         return -ETIMEDOUT;
 139                 }
 140         } while (ptr == end);
 141
 142         /*
 143          * ptr now points to the header byte. Copy any valid data to the
 144          * start of our buffer
 145          */
 146         todo = end - ++ptr;
 147         BUG_ON(todo < 0 || todo > ec_dev->din_size);
 148         todo = min(todo, need_len);
 149         memmove(ec_dev->din, ptr, todo);
 150         ptr = ec_dev->din + todo;
 151         dev_dbg(ec_dev->dev, "need %d, got %d bytes from preamble\n",
 152                  need_len, todo);
 153         need_len -= todo;
 154
 155         /* Receive data until we have it all */
 156         while (need_len > 0) {
 157                 /*
 158                  * We can't support transfers larger than the SPI FIFO size
 159                  * unless we have DMA. We don't have DMA on the ISP SPI ports
 160                  * for Exynos. We need a way of asking SPI driver for
 161                  * maximum-supported transfer size.
 162                  */
 163                 todo = min(need_len, 256);
 164                 dev_dbg(ec_dev->dev, "loop, todo=%d, need_len=%d, ptr=%zd\n",
 165                         todo, need_len, ptr - ec_dev->din);
 166
 167                 memset(&trans, 0, sizeof(trans));
 168                 trans.cs_change = 1;
 169                 trans.rx_buf = ptr;
 170                 trans.len = todo;
 171                 spi_message_init(&msg);
 172                 spi_message_add_tail(&trans, &msg);
 173
 174                 /* send command to EC and read answer */
 175                 BUG_ON((u8 *)trans.rx_buf - ec_dev->din + todo >
 176                                 ec_dev->din_size);
 177                 ret = spi_sync(ec_spi->spi, &msg);
 178                 if (ret < 0) {
 179                         dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
 180                         return ret;
 181                 }
 182
 183                 debug_packet(ec_dev->dev, "interim", ptr, todo);
 184                 ptr += todo;
 185                 need_len -= todo;
 186         }
 187
 188         dev_dbg(ec_dev->dev, "loop done, ptr=%zd\n", ptr - ec_dev->din);
 189
 190         return 0;
 191 }
 192
 193 /**
 194  * cros_ec_command_spi_xfer - Transfer a message over SPI and receive the reply
 195  *
 196  * @ec_dev: ChromeOS EC device
 197  * @ec_msg: Message to transfer
 198  */
 199 static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev,
 200                                     struct cros_ec_msg *ec_msg)
 201 {
 202         struct cros_ec_spi *ec_spi = ec_dev->priv;
 203         struct spi_transfer trans;
 204         struct spi_message msg;
 205         int i, len;
 206         u8 *ptr;
 207         int sum;
 208         int ret = 0, final_ret;
 209         struct timespec ts;
 210
 211         len = cros_ec_prepare_tx(ec_dev, ec_msg);
 212         dev_dbg(ec_dev->dev, "prepared, len=%d\n", len);
 213
 214         /* If it's too soon to do another transaction, wait */
 215         if (ec_spi->last_transfer_ns) {
 216                 struct timespec ts;
 217                 unsigned long delay;    /* The delay completed so far */
 218
 219                 ktime_get_ts(&ts);
 220                 delay = timespec_to_ns(&ts) - ec_spi->last_transfer_ns;
 221                 if (delay < EC_SPI_RECOVERY_TIME_NS)
 222                         ndelay(delay);
 223         }
 224
 225         /* Transmit phase - send our message */
 226         debug_packet(ec_dev->dev, "out", ec_dev->dout, len);
 227         memset(&trans, 0, sizeof(trans));
 228         trans.tx_buf = ec_dev->dout;
 229         trans.len = len;
 230         trans.cs_change = 1;
 231         spi_message_init(&msg);
 232         spi_message_add_tail(&trans, &msg);
 233         ret = spi_sync(ec_spi->spi, &msg);
 234
 235         /* Get the response */
 236         if (!ret) {
 237                 ret = cros_ec_spi_receive_response(ec_dev,
 238                                 ec_msg->in_len + EC_MSG_TX_PROTO_BYTES);
 239         } else {
 240                 dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
 241         }
 242
 243         /* turn off CS */
 244         spi_message_init(&msg);
 245
 246         if (ec_spi->end_of_msg_delay) {
 247                 /*
 248                  * Add delay for last transaction, to ensure the rising edge
 249                  * doesn't come too soon after the end of the data.
 250                  */
 251                 memset(&trans, 0, sizeof(trans));
 252                 trans.delay_usecs = ec_spi->end_of_msg_delay;
 253                 spi_message_add_tail(&trans, &msg);
 254         }
 255
 256         final_ret = spi_sync(ec_spi->spi, &msg);
 257         ktime_get_ts(&ts);
 258         ec_spi->last_transfer_ns = timespec_to_ns(&ts);
 259         if (!ret)
 260                 ret = final_ret;
 261         if (ret < 0) {
 262                 dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
 263                 return ret;
 264         }
 265
 266         /* check response error code */
 267         ptr = ec_dev->din;
 268         if (ptr[0]) {
 269                 dev_warn(ec_dev->dev, "command 0x%02x returned an error %d\n",
 270                          ec_msg->cmd, ptr[0]);
 271                 debug_packet(ec_dev->dev, "in_err", ptr, len);
 272                 return -EINVAL;
 273         }
 274         len = ptr[1];
 275         sum = ptr[0] + ptr[1];
 276         if (len > ec_msg->in_len) {
 277                 dev_err(ec_dev->dev, "packet too long (%d bytes, expected %d)",
 278                         len, ec_msg->in_len);
 279                 return -ENOSPC;
 280         }
 281
 282         /* copy response packet payload and compute checksum */
 283         for (i = 0; i < len; i++) {
 284                 sum += ptr[i + 2];
 285                 if (ec_msg->in_len)
 286                         ec_msg->in_buf[i] = ptr[i + 2];
 287         }
 288         sum &= 0xff;
 289
 290         debug_packet(ec_dev->dev, "in", ptr, len + 3);
 291
 292         if (sum != ptr[len + 2]) {
 293                 dev_err(ec_dev->dev,
 294                         "bad packet checksum, expected %02x, got %02x\n",
 295                         sum, ptr[len + 2]);
 296                 return -EBADMSG;
 297         }
 298
 299         return 0;
 300 }
 301
 302 static void cros_ec_spi_dt_probe(struct cros_ec_spi *ec_spi, struct device *dev)
 303 {
 304         struct device_node *np = dev->of_node;
 305         u32 val;
 306         int ret;
 307
 308         ret = of_property_read_u32(np, "google,cros-ec-spi-msg-delay", &val);
 309         if (!ret)
 310                 ec_spi->end_of_msg_delay = val;
 311 }
 312
 313 static int cros_ec_spi_probe(struct spi_device *spi)
 314 {
 315         struct device *dev = &spi->dev;
 316         struct cros_ec_device *ec_dev;
 317         struct cros_ec_spi *ec_spi;
 318         int err;
 319
 320         spi->bits_per_word = 8;
 321         spi->mode = SPI_MODE_0;
 322         err = spi_setup(spi);
 323         if (err < 0)
 324                 return err;
 325
 326         ec_spi = devm_kzalloc(dev, sizeof(*ec_spi), GFP_KERNEL);
 327         if (ec_spi == NULL)
 328                 return -ENOMEM;
 329         ec_spi->spi = spi;
 330         ec_dev = devm_kzalloc(dev, sizeof(*ec_dev), GFP_KERNEL);
 331         if (!ec_dev)
 332                 return -ENOMEM;
 333
 334         /* Check for any DT properties */
 335         cros_ec_spi_dt_probe(ec_spi, dev);
 336
 337         spi_set_drvdata(spi, ec_dev);
 338         ec_dev->name = "SPI";
 339         ec_dev->dev = dev;
 340         ec_dev->priv = ec_spi;
 341         ec_dev->irq = spi->irq;
 342         ec_dev->command_xfer = cros_ec_command_spi_xfer;
 343         ec_dev->ec_name = ec_spi->spi->modalias;
 344         ec_dev->phys_name = dev_name(&ec_spi->spi->dev);
 345         ec_dev->parent = &ec_spi->spi->dev;
 346         ec_dev->din_size = EC_MSG_BYTES + EC_MSG_PREAMBLE_COUNT;
 347         ec_dev->dout_size = EC_MSG_BYTES;
 348
 349         err = cros_ec_register(ec_dev);
 350         if (err) {
 351                 dev_err(dev, "cannot register EC\n");
 352                 return err;
 353         }
 354
 355         return 0;
 356 }
 357
 358 static int cros_ec_spi_remove(struct spi_device *spi)
 359 {
 360         struct cros_ec_device *ec_dev;
 361
 362         ec_dev = spi_get_drvdata(spi);
 363         cros_ec_remove(ec_dev);
 364
 365         return 0;
 366 }
 367
 368 #ifdef CONFIG_PM_SLEEP
 369 static int cros_ec_spi_suspend(struct device *dev)
 370 {
 371         struct cros_ec_device *ec_dev = dev_get_drvdata(dev);
 372
 373         return cros_ec_suspend(ec_dev);
 374 }
 375
 376 static int cros_ec_spi_resume(struct device *dev)
 377 {
 378         struct cros_ec_device *ec_dev = dev_get_drvdata(dev);
 379
 380         return cros_ec_resume(ec_dev);
 381 }
 382 #endif
 383
 384 static SIMPLE_DEV_PM_OPS(cros_ec_spi_pm_ops, cros_ec_spi_suspend,
 385                          cros_ec_spi_resume);
 386
 387 static const struct spi_device_id cros_ec_spi_id[] = {
 388         { "cros-ec-spi", 0 },
 389         { }
 390 };
 391 MODULE_DEVICE_TABLE(spi, cros_ec_spi_id);
 392
 393 static struct spi_driver cros_ec_driver_spi = {
 394         .driver = {
 395                 .name   = "cros-ec-spi",
 396                 .owner  = THIS_MODULE,
 397                 .pm     = &cros_ec_spi_pm_ops,
 398         },
 399         .probe          = cros_ec_spi_probe,
 400         .remove         = cros_ec_spi_remove,
 401         .id_table       = cros_ec_spi_id,
 402 };
 403
 404 module_spi_driver(cros_ec_driver_spi);
 405
 406 MODULE_LICENSE("GPL v2");
 407 MODULE_DESCRIPTION("ChromeOS EC multi function device (SPI)");