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