root/drivers/tty/ehv_bytechan.c

DEFINITIONS

1. enable_tx_interrupt
2. disable_tx_interrupt
3. find_console_handle
4. local_ev_byte_channel_send
5. byte_channel_spin_send
6. ehv_bc_udbg_putc
7. udbg_init_ehv_bc
8. ehv_bc_console_byte_channel_send
9. ehv_bc_console_write
10. ehv_bc_console_device
11. ehv_bc_console_init
12. ehv_bc_tty_rx_isr
13. ehv_bc_tx_dequeue
14. ehv_bc_tty_tx_isr
15. ehv_bc_tty_write
16. ehv_bc_tty_open
17. ehv_bc_tty_close
18. ehv_bc_tty_write_room
19. ehv_bc_tty_throttle
20. ehv_bc_tty_unthrottle
21. ehv_bc_tty_hangup
22. ehv_bc_tty_port_activate
23. ehv_bc_tty_port_shutdown
24. ehv_bc_tty_probe
25. ehv_bc_init

   1 // SPDX-License-Identifier: GPL-2.0
   2 /* ePAPR hypervisor byte channel device driver
   3  *
   4  * Copyright 2009-2011 Freescale Semiconductor, Inc.
   5  *
   6  * Author: Timur Tabi <timur@freescale.com>
   7  *
   8  * This driver support three distinct interfaces, all of which are related to
   9  * ePAPR hypervisor byte channels.
  10  *
  11  * 1) An early-console (udbg) driver.  This provides early console output
  12  * through a byte channel.  The byte channel handle must be specified in a
  13  * Kconfig option.
  14  *
  15  * 2) A normal console driver.  Output is sent to the byte channel designated
  16  * for stdout in the device tree.  The console driver is for handling kernel
  17  * printk calls.
  18  *
  19  * 3) A tty driver, which is used to handle user-space input and output.  The
  20  * byte channel used for the console is designated as the default tty.
  21  */
  22 
  23 #include <linux/init.h>
  24 #include <linux/slab.h>
  25 #include <linux/err.h>
  26 #include <linux/interrupt.h>
  27 #include <linux/fs.h>
  28 #include <linux/poll.h>
  29 #include <asm/epapr_hcalls.h>
  30 #include <linux/of.h>
  31 #include <linux/of_irq.h>
  32 #include <linux/platform_device.h>
  33 #include <linux/cdev.h>
  34 #include <linux/console.h>
  35 #include <linux/tty.h>
  36 #include <linux/tty_flip.h>
  37 #include <linux/circ_buf.h>
  38 #include <asm/udbg.h>
  39 
  40 /* The size of the transmit circular buffer.  This must be a power of two. */
  41 #define BUF_SIZE        2048
  42 
  43 /* Per-byte channel private data */
  44 struct ehv_bc_data {
  45         struct device *dev;
  46         struct tty_port port;
  47         uint32_t handle;
  48         unsigned int rx_irq;
  49         unsigned int tx_irq;
  50 
  51         spinlock_t lock;        /* lock for transmit buffer */
  52         unsigned char buf[BUF_SIZE];    /* transmit circular buffer */
  53         unsigned int head;      /* circular buffer head */
  54         unsigned int tail;      /* circular buffer tail */
  55 
  56         int tx_irq_enabled;     /* true == TX interrupt is enabled */
  57 };
  58 
  59 /* Array of byte channel objects */
  60 static struct ehv_bc_data *bcs;
  61 
  62 /* Byte channel handle for stdout (and stdin), taken from device tree */
  63 static unsigned int stdout_bc;
  64 
  65 /* Virtual IRQ for the byte channel handle for stdin, taken from device tree */
  66 static unsigned int stdout_irq;
  67 
  68 /**************************** SUPPORT FUNCTIONS ****************************/
  69 
  70 /*
  71  * Enable the transmit interrupt
  72  *
  73  * Unlike a serial device, byte channels have no mechanism for disabling their
  74  * own receive or transmit interrupts.  To emulate that feature, we toggle
  75  * the IRQ in the kernel.
  76  *
  77  * We cannot just blindly call enable_irq() or disable_irq(), because these
  78  * calls are reference counted.  This means that we cannot call enable_irq()
  79  * if interrupts are already enabled.  This can happen in two situations:
  80  *
  81  * 1. The tty layer makes two back-to-back calls to ehv_bc_tty_write()
  82  * 2. A transmit interrupt occurs while executing ehv_bc_tx_dequeue()
  83  *
  84  * To work around this, we keep a flag to tell us if the IRQ is enabled or not.
  85  */
  86 static void enable_tx_interrupt(struct ehv_bc_data *bc)
  87 {
  88         if (!bc->tx_irq_enabled) {
  89                 enable_irq(bc->tx_irq);
  90                 bc->tx_irq_enabled = 1;
  91         }
  92 }
  93 
  94 static void disable_tx_interrupt(struct ehv_bc_data *bc)
  95 {
  96         if (bc->tx_irq_enabled) {
  97                 disable_irq_nosync(bc->tx_irq);
  98                 bc->tx_irq_enabled = 0;
  99         }
 100 }
 101 
 102 /*
 103  * find the byte channel handle to use for the console
 104  *
 105  * The byte channel to be used for the console is specified via a "stdout"
 106  * property in the /chosen node.
 107  */
 108 static int find_console_handle(void)
 109 {
 110         struct device_node *np = of_stdout;
 111         const uint32_t *iprop;
 112 
 113         /* We don't care what the aliased node is actually called.  We only
 114          * care if it's compatible with "epapr,hv-byte-channel", because that
 115          * indicates that it's a byte channel node.
 116          */
 117         if (!np || !of_device_is_compatible(np, "epapr,hv-byte-channel"))
 118                 return 0;
 119 
 120         stdout_irq = irq_of_parse_and_map(np, 0);
 121         if (stdout_irq == NO_IRQ) {
 122                 pr_err("ehv-bc: no 'interrupts' property in %pOF node\n", np);
 123                 return 0;
 124         }
 125 
 126         /*
 127          * The 'hv-handle' property contains the handle for this byte channel.
 128          */
 129         iprop = of_get_property(np, "hv-handle", NULL);
 130         if (!iprop) {
 131                 pr_err("ehv-bc: no 'hv-handle' property in %pOFn node\n",
 132                        np);
 133                 return 0;
 134         }
 135         stdout_bc = be32_to_cpu(*iprop);
 136         return 1;
 137 }
 138 
 139 static unsigned int local_ev_byte_channel_send(unsigned int handle,
 140                                                unsigned int *count,
 141                                                const char *p)
 142 {
 143         char buffer[EV_BYTE_CHANNEL_MAX_BYTES];
 144         unsigned int c = *count;
 145 
 146         if (c < sizeof(buffer)) {
 147                 memcpy(buffer, p, c);
 148                 memset(&buffer[c], 0, sizeof(buffer) - c);
 149                 p = buffer;
 150         }
 151         return ev_byte_channel_send(handle, count, p);
 152 }
 153 
 154 /*************************** EARLY CONSOLE DRIVER ***************************/
 155 
 156 #ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC
 157 
 158 /*
 159  * send a byte to a byte channel, wait if necessary
 160  *
 161  * This function sends a byte to a byte channel, and it waits and
 162  * retries if the byte channel is full.  It returns if the character
 163  * has been sent, or if some error has occurred.
 164  *
 165  */
 166 static void byte_channel_spin_send(const char data)
 167 {
 168         int ret, count;
 169 
 170         do {
 171                 count = 1;
 172                 ret = local_ev_byte_channel_send(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
 173                                            &count, &data);
 174         } while (ret == EV_EAGAIN);
 175 }
 176 
 177 /*
 178  * The udbg subsystem calls this function to display a single character.
 179  * We convert CR to a CR/LF.
 180  */
 181 static void ehv_bc_udbg_putc(char c)
 182 {
 183         if (c == '\n')
 184                 byte_channel_spin_send('\r');
 185 
 186         byte_channel_spin_send(c);
 187 }
 188 
 189 /*
 190  * early console initialization
 191  *
 192  * PowerPC kernels support an early printk console, also known as udbg.
 193  * This function must be called via the ppc_md.init_early function pointer.
 194  * At this point, the device tree has been unflattened, so we can obtain the
 195  * byte channel handle for stdout.
 196  *
 197  * We only support displaying of characters (putc).  We do not support
 198  * keyboard input.
 199  */
 200 void __init udbg_init_ehv_bc(void)
 201 {
 202         unsigned int rx_count, tx_count;
 203         unsigned int ret;
 204 
 205         /* Verify the byte channel handle */
 206         ret = ev_byte_channel_poll(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
 207                                    &rx_count, &tx_count);
 208         if (ret)
 209                 return;
 210 
 211         udbg_putc = ehv_bc_udbg_putc;
 212         register_early_udbg_console();
 213 
 214         udbg_printf("ehv-bc: early console using byte channel handle %u\n",
 215                     CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
 216 }
 217 
 218 #endif
 219 
 220 /****************************** CONSOLE DRIVER ******************************/
 221 
 222 static struct tty_driver *ehv_bc_driver;
 223 
 224 /*
 225  * Byte channel console sending worker function.
 226  *
 227  * For consoles, if the output buffer is full, we should just spin until it
 228  * clears.
 229  */
 230 static int ehv_bc_console_byte_channel_send(unsigned int handle, const char *s,
 231                              unsigned int count)
 232 {
 233         unsigned int len;
 234         int ret = 0;
 235 
 236         while (count) {
 237                 len = min_t(unsigned int, count, EV_BYTE_CHANNEL_MAX_BYTES);
 238                 do {
 239                         ret = local_ev_byte_channel_send(handle, &len, s);
 240                 } while (ret == EV_EAGAIN);
 241                 count -= len;
 242                 s += len;
 243         }
 244 
 245         return ret;
 246 }
 247 
 248 /*
 249  * write a string to the console
 250  *
 251  * This function gets called to write a string from the kernel, typically from
 252  * a printk().  This function spins until all data is written.
 253  *
 254  * We copy the data to a temporary buffer because we need to insert a \r in
 255  * front of every \n.  It's more efficient to copy the data to the buffer than
 256  * it is to make multiple hcalls for each character or each newline.
 257  */
 258 static void ehv_bc_console_write(struct console *co, const char *s,
 259                                  unsigned int count)
 260 {
 261         char s2[EV_BYTE_CHANNEL_MAX_BYTES];
 262         unsigned int i, j = 0;
 263         char c;
 264 
 265         for (i = 0; i < count; i++) {
 266                 c = *s++;
 267 
 268                 if (c == '\n')
 269                         s2[j++] = '\r';
 270 
 271                 s2[j++] = c;
 272                 if (j >= (EV_BYTE_CHANNEL_MAX_BYTES - 1)) {
 273                         if (ehv_bc_console_byte_channel_send(stdout_bc, s2, j))
 274                                 return;
 275                         j = 0;
 276                 }
 277         }
 278 
 279         if (j)
 280                 ehv_bc_console_byte_channel_send(stdout_bc, s2, j);
 281 }
 282 
 283 /*
 284  * When /dev/console is opened, the kernel iterates the console list looking
 285  * for one with ->device and then calls that method. On success, it expects
 286  * the passed-in int* to contain the minor number to use.
 287  */
 288 static struct tty_driver *ehv_bc_console_device(struct console *co, int *index)
 289 {
 290         *index = co->index;
 291 
 292         return ehv_bc_driver;
 293 }
 294 
 295 static struct console ehv_bc_console = {
 296         .name           = "ttyEHV",
 297         .write          = ehv_bc_console_write,
 298         .device         = ehv_bc_console_device,
 299         .flags          = CON_PRINTBUFFER | CON_ENABLED,
 300 };
 301 
 302 /*
 303  * Console initialization
 304  *
 305  * This is the first function that is called after the device tree is
 306  * available, so here is where we determine the byte channel handle and IRQ for
 307  * stdout/stdin, even though that information is used by the tty and character
 308  * drivers.
 309  */
 310 static int __init ehv_bc_console_init(void)
 311 {
 312         if (!find_console_handle()) {
 313                 pr_debug("ehv-bc: stdout is not a byte channel\n");
 314                 return -ENODEV;
 315         }
 316 
 317 #ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC
 318         /* Print a friendly warning if the user chose the wrong byte channel
 319          * handle for udbg.
 320          */
 321         if (stdout_bc != CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE)
 322                 pr_warn("ehv-bc: udbg handle %u is not the stdout handle\n",
 323                         CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
 324 #endif
 325 
 326         /* add_preferred_console() must be called before register_console(),
 327            otherwise it won't work.  However, we don't want to enumerate all the
 328            byte channels here, either, since we only care about one. */
 329 
 330         add_preferred_console(ehv_bc_console.name, ehv_bc_console.index, NULL);
 331         register_console(&ehv_bc_console);
 332 
 333         pr_info("ehv-bc: registered console driver for byte channel %u\n",
 334                 stdout_bc);
 335 
 336         return 0;
 337 }
 338 console_initcall(ehv_bc_console_init);
 339 
 340 /******************************** TTY DRIVER ********************************/
 341 
 342 /*
 343  * byte channel receive interrupt handler
 344  *
 345  * This ISR is called whenever data is available on a byte channel.
 346  */
 347 static irqreturn_t ehv_bc_tty_rx_isr(int irq, void *data)
 348 {
 349         struct ehv_bc_data *bc = data;
 350         unsigned int rx_count, tx_count, len;
 351         int count;
 352         char buffer[EV_BYTE_CHANNEL_MAX_BYTES];
 353         int ret;
 354 
 355         /* Find out how much data needs to be read, and then ask the TTY layer
 356          * if it can handle that much.  We want to ensure that every byte we
 357          * read from the byte channel will be accepted by the TTY layer.
 358          */
 359         ev_byte_channel_poll(bc->handle, &rx_count, &tx_count);
 360         count = tty_buffer_request_room(&bc->port, rx_count);
 361 
 362         /* 'count' is the maximum amount of data the TTY layer can accept at
 363          * this time.  However, during testing, I was never able to get 'count'
 364          * to be less than 'rx_count'.  I'm not sure whether I'm calling it
 365          * correctly.
 366          */
 367 
 368         while (count > 0) {
 369                 len = min_t(unsigned int, count, sizeof(buffer));
 370 
 371                 /* Read some data from the byte channel.  This function will
 372                  * never return more than EV_BYTE_CHANNEL_MAX_BYTES bytes.
 373                  */
 374                 ev_byte_channel_receive(bc->handle, &len, buffer);
 375 
 376                 /* 'len' is now the amount of data that's been received. 'len'
 377                  * can't be zero, and most likely it's equal to one.
 378                  */
 379 
 380                 /* Pass the received data to the tty layer. */
 381                 ret = tty_insert_flip_string(&bc->port, buffer, len);
 382 
 383                 /* 'ret' is the number of bytes that the TTY layer accepted.
 384                  * If it's not equal to 'len', then it means the buffer is
 385                  * full, which should never happen.  If it does happen, we can
 386                  * exit gracefully, but we drop the last 'len - ret' characters
 387                  * that we read from the byte channel.
 388                  */
 389                 if (ret != len)
 390                         break;
 391 
 392                 count -= len;
 393         }
 394 
 395         /* Tell the tty layer that we're done. */
 396         tty_flip_buffer_push(&bc->port);
 397 
 398         return IRQ_HANDLED;
 399 }
 400 
 401 /*
 402  * dequeue the transmit buffer to the hypervisor
 403  *
 404  * This function, which can be called in interrupt context, dequeues as much
 405  * data as possible from the transmit buffer to the byte channel.
 406  */
 407 static void ehv_bc_tx_dequeue(struct ehv_bc_data *bc)
 408 {
 409         unsigned int count;
 410         unsigned int len, ret;
 411         unsigned long flags;
 412 
 413         do {
 414                 spin_lock_irqsave(&bc->lock, flags);
 415                 len = min_t(unsigned int,
 416                             CIRC_CNT_TO_END(bc->head, bc->tail, BUF_SIZE),
 417                             EV_BYTE_CHANNEL_MAX_BYTES);
 418 
 419                 ret = local_ev_byte_channel_send(bc->handle, &len, bc->buf + bc->tail);
 420 
 421                 /* 'len' is valid only if the return code is 0 or EV_EAGAIN */
 422                 if (!ret || (ret == EV_EAGAIN))
 423                         bc->tail = (bc->tail + len) & (BUF_SIZE - 1);
 424 
 425                 count = CIRC_CNT(bc->head, bc->tail, BUF_SIZE);
 426                 spin_unlock_irqrestore(&bc->lock, flags);
 427         } while (count && !ret);
 428 
 429         spin_lock_irqsave(&bc->lock, flags);
 430         if (CIRC_CNT(bc->head, bc->tail, BUF_SIZE))
 431                 /*
 432                  * If we haven't emptied the buffer, then enable the TX IRQ.
 433                  * We'll get an interrupt when there's more room in the
 434                  * hypervisor's output buffer.
 435                  */
 436                 enable_tx_interrupt(bc);
 437         else
 438                 disable_tx_interrupt(bc);
 439         spin_unlock_irqrestore(&bc->lock, flags);
 440 }
 441 
 442 /*
 443  * byte channel transmit interrupt handler
 444  *
 445  * This ISR is called whenever space becomes available for transmitting
 446  * characters on a byte channel.
 447  */
 448 static irqreturn_t ehv_bc_tty_tx_isr(int irq, void *data)
 449 {
 450         struct ehv_bc_data *bc = data;
 451 
 452         ehv_bc_tx_dequeue(bc);
 453         tty_port_tty_wakeup(&bc->port);
 454 
 455         return IRQ_HANDLED;
 456 }
 457 
 458 /*
 459  * This function is called when the tty layer has data for us send.  We store
 460  * the data first in a circular buffer, and then dequeue as much of that data
 461  * as possible.
 462  *
 463  * We don't need to worry about whether there is enough room in the buffer for
 464  * all the data.  The purpose of ehv_bc_tty_write_room() is to tell the tty
 465  * layer how much data it can safely send to us.  We guarantee that
 466  * ehv_bc_tty_write_room() will never lie, so the tty layer will never send us
 467  * too much data.
 468  */
 469 static int ehv_bc_tty_write(struct tty_struct *ttys, const unsigned char *s,
 470                             int count)
 471 {
 472         struct ehv_bc_data *bc = ttys->driver_data;
 473         unsigned long flags;
 474         unsigned int len;
 475         unsigned int written = 0;
 476 
 477         while (1) {
 478                 spin_lock_irqsave(&bc->lock, flags);
 479                 len = CIRC_SPACE_TO_END(bc->head, bc->tail, BUF_SIZE);
 480                 if (count < len)
 481                         len = count;
 482                 if (len) {
 483                         memcpy(bc->buf + bc->head, s, len);
 484                         bc->head = (bc->head + len) & (BUF_SIZE - 1);
 485                 }
 486                 spin_unlock_irqrestore(&bc->lock, flags);
 487                 if (!len)
 488                         break;
 489 
 490                 s += len;
 491                 count -= len;
 492                 written += len;
 493         }
 494 
 495         ehv_bc_tx_dequeue(bc);
 496 
 497         return written;
 498 }
 499 
 500 /*
 501  * This function can be called multiple times for a given tty_struct, which is
 502  * why we initialize bc->ttys in ehv_bc_tty_port_activate() instead.
 503  *
 504  * The tty layer will still call this function even if the device was not
 505  * registered (i.e. tty_register_device() was not called).  This happens
 506  * because tty_register_device() is optional and some legacy drivers don't
 507  * use it.  So we need to check for that.
 508  */
 509 static int ehv_bc_tty_open(struct tty_struct *ttys, struct file *filp)
 510 {
 511         struct ehv_bc_data *bc = &bcs[ttys->index];
 512 
 513         if (!bc->dev)
 514                 return -ENODEV;
 515 
 516         return tty_port_open(&bc->port, ttys, filp);
 517 }
 518 
 519 /*
 520  * Amazingly, if ehv_bc_tty_open() returns an error code, the tty layer will
 521  * still call this function to close the tty device.  So we can't assume that
 522  * the tty port has been initialized.
 523  */
 524 static void ehv_bc_tty_close(struct tty_struct *ttys, struct file *filp)
 525 {
 526         struct ehv_bc_data *bc = &bcs[ttys->index];
 527 
 528         if (bc->dev)
 529                 tty_port_close(&bc->port, ttys, filp);
 530 }
 531 
 532 /*
 533  * Return the amount of space in the output buffer
 534  *
 535  * This is actually a contract between the driver and the tty layer outlining
 536  * how much write room the driver can guarantee will be sent OR BUFFERED.  This
 537  * driver MUST honor the return value.
 538  */
 539 static int ehv_bc_tty_write_room(struct tty_struct *ttys)
 540 {
 541         struct ehv_bc_data *bc = ttys->driver_data;
 542         unsigned long flags;
 543         int count;
 544 
 545         spin_lock_irqsave(&bc->lock, flags);
 546         count = CIRC_SPACE(bc->head, bc->tail, BUF_SIZE);
 547         spin_unlock_irqrestore(&bc->lock, flags);
 548 
 549         return count;
 550 }
 551 
 552 /*
 553  * Stop sending data to the tty layer
 554  *
 555  * This function is called when the tty layer's input buffers are getting full,
 556  * so the driver should stop sending it data.  The easiest way to do this is to
 557  * disable the RX IRQ, which will prevent ehv_bc_tty_rx_isr() from being
 558  * called.
 559  *
 560  * The hypervisor will continue to queue up any incoming data.  If there is any
 561  * data in the queue when the RX interrupt is enabled, we'll immediately get an
 562  * RX interrupt.
 563  */
 564 static void ehv_bc_tty_throttle(struct tty_struct *ttys)
 565 {
 566         struct ehv_bc_data *bc = ttys->driver_data;
 567 
 568         disable_irq(bc->rx_irq);
 569 }
 570 
 571 /*
 572  * Resume sending data to the tty layer
 573  *
 574  * This function is called after previously calling ehv_bc_tty_throttle().  The
 575  * tty layer's input buffers now have more room, so the driver can resume
 576  * sending it data.
 577  */
 578 static void ehv_bc_tty_unthrottle(struct tty_struct *ttys)
 579 {
 580         struct ehv_bc_data *bc = ttys->driver_data;
 581 
 582         /* If there is any data in the queue when the RX interrupt is enabled,
 583          * we'll immediately get an RX interrupt.
 584          */
 585         enable_irq(bc->rx_irq);
 586 }
 587 
 588 static void ehv_bc_tty_hangup(struct tty_struct *ttys)
 589 {
 590         struct ehv_bc_data *bc = ttys->driver_data;
 591 
 592         ehv_bc_tx_dequeue(bc);
 593         tty_port_hangup(&bc->port);
 594 }
 595 
 596 /*
 597  * TTY driver operations
 598  *
 599  * If we could ask the hypervisor how much data is still in the TX buffer, or
 600  * at least how big the TX buffers are, then we could implement the
 601  * .wait_until_sent and .chars_in_buffer functions.
 602  */
 603 static const struct tty_operations ehv_bc_ops = {
 604         .open           = ehv_bc_tty_open,
 605         .close          = ehv_bc_tty_close,
 606         .write          = ehv_bc_tty_write,
 607         .write_room     = ehv_bc_tty_write_room,
 608         .throttle       = ehv_bc_tty_throttle,
 609         .unthrottle     = ehv_bc_tty_unthrottle,
 610         .hangup         = ehv_bc_tty_hangup,
 611 };
 612 
 613 /*
 614  * initialize the TTY port
 615  *
 616  * This function will only be called once, no matter how many times
 617  * ehv_bc_tty_open() is called.  That's why we register the ISR here, and also
 618  * why we initialize tty_struct-related variables here.
 619  */
 620 static int ehv_bc_tty_port_activate(struct tty_port *port,
 621                                     struct tty_struct *ttys)
 622 {
 623         struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);
 624         int ret;
 625 
 626         ttys->driver_data = bc;
 627 
 628         ret = request_irq(bc->rx_irq, ehv_bc_tty_rx_isr, 0, "ehv-bc", bc);
 629         if (ret < 0) {
 630                 dev_err(bc->dev, "could not request rx irq %u (ret=%i)\n",
 631                        bc->rx_irq, ret);
 632                 return ret;
 633         }
 634 
 635         /* request_irq also enables the IRQ */
 636         bc->tx_irq_enabled = 1;
 637 
 638         ret = request_irq(bc->tx_irq, ehv_bc_tty_tx_isr, 0, "ehv-bc", bc);
 639         if (ret < 0) {
 640                 dev_err(bc->dev, "could not request tx irq %u (ret=%i)\n",
 641                        bc->tx_irq, ret);
 642                 free_irq(bc->rx_irq, bc);
 643                 return ret;
 644         }
 645 
 646         /* The TX IRQ is enabled only when we can't write all the data to the
 647          * byte channel at once, so by default it's disabled.
 648          */
 649         disable_tx_interrupt(bc);
 650 
 651         return 0;
 652 }
 653 
 654 static void ehv_bc_tty_port_shutdown(struct tty_port *port)
 655 {
 656         struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);
 657 
 658         free_irq(bc->tx_irq, bc);
 659         free_irq(bc->rx_irq, bc);
 660 }
 661 
 662 static const struct tty_port_operations ehv_bc_tty_port_ops = {
 663         .activate = ehv_bc_tty_port_activate,
 664         .shutdown = ehv_bc_tty_port_shutdown,
 665 };
 666 
 667 static int ehv_bc_tty_probe(struct platform_device *pdev)
 668 {
 669         struct device_node *np = pdev->dev.of_node;
 670         struct ehv_bc_data *bc;
 671         const uint32_t *iprop;
 672         unsigned int handle;
 673         int ret;
 674         static unsigned int index = 1;
 675         unsigned int i;
 676 
 677         iprop = of_get_property(np, "hv-handle", NULL);
 678         if (!iprop) {
 679                 dev_err(&pdev->dev, "no 'hv-handle' property in %pOFn node\n",
 680                         np);
 681                 return -ENODEV;
 682         }
 683 
 684         /* We already told the console layer that the index for the console
 685          * device is zero, so we need to make sure that we use that index when
 686          * we probe the console byte channel node.
 687          */
 688         handle = be32_to_cpu(*iprop);
 689         i = (handle == stdout_bc) ? 0 : index++;
 690         bc = &bcs[i];
 691 
 692         bc->handle = handle;
 693         bc->head = 0;
 694         bc->tail = 0;
 695         spin_lock_init(&bc->lock);
 696 
 697         bc->rx_irq = irq_of_parse_and_map(np, 0);
 698         bc->tx_irq = irq_of_parse_and_map(np, 1);
 699         if ((bc->rx_irq == NO_IRQ) || (bc->tx_irq == NO_IRQ)) {
 700                 dev_err(&pdev->dev, "no 'interrupts' property in %pOFn node\n",
 701                         np);
 702                 ret = -ENODEV;
 703                 goto error;
 704         }
 705 
 706         tty_port_init(&bc->port);
 707         bc->port.ops = &ehv_bc_tty_port_ops;
 708 
 709         bc->dev = tty_port_register_device(&bc->port, ehv_bc_driver, i,
 710                         &pdev->dev);
 711         if (IS_ERR(bc->dev)) {
 712                 ret = PTR_ERR(bc->dev);
 713                 dev_err(&pdev->dev, "could not register tty (ret=%i)\n", ret);
 714                 goto error;
 715         }
 716 
 717         dev_set_drvdata(&pdev->dev, bc);
 718 
 719         dev_info(&pdev->dev, "registered /dev/%s%u for byte channel %u\n",
 720                 ehv_bc_driver->name, i, bc->handle);
 721 
 722         return 0;
 723 
 724 error:
 725         tty_port_destroy(&bc->port);
 726         irq_dispose_mapping(bc->tx_irq);
 727         irq_dispose_mapping(bc->rx_irq);
 728 
 729         memset(bc, 0, sizeof(struct ehv_bc_data));
 730         return ret;
 731 }
 732 
 733 static const struct of_device_id ehv_bc_tty_of_ids[] = {
 734         { .compatible = "epapr,hv-byte-channel" },
 735         {}
 736 };
 737 
 738 static struct platform_driver ehv_bc_tty_driver = {
 739         .driver = {
 740                 .name = "ehv-bc",
 741                 .of_match_table = ehv_bc_tty_of_ids,
 742                 .suppress_bind_attrs = true,
 743         },
 744         .probe          = ehv_bc_tty_probe,
 745 };
 746 
 747 /**
 748  * ehv_bc_init - ePAPR hypervisor byte channel driver initialization
 749  *
 750  * This function is called when this driver is loaded.
 751  */
 752 static int __init ehv_bc_init(void)
 753 {
 754         struct device_node *np;
 755         unsigned int count = 0; /* Number of elements in bcs[] */
 756         int ret;
 757 
 758         pr_info("ePAPR hypervisor byte channel driver\n");
 759 
 760         /* Count the number of byte channels */
 761         for_each_compatible_node(np, NULL, "epapr,hv-byte-channel")
 762                 count++;
 763 
 764         if (!count)
 765                 return -ENODEV;
 766 
 767         /* The array index of an element in bcs[] is the same as the tty index
 768          * for that element.  If you know the address of an element in the
 769          * array, then you can use pointer math (e.g. "bc - bcs") to get its
 770          * tty index.
 771          */
 772         bcs = kcalloc(count, sizeof(struct ehv_bc_data), GFP_KERNEL);
 773         if (!bcs)
 774                 return -ENOMEM;
 775 
 776         ehv_bc_driver = alloc_tty_driver(count);
 777         if (!ehv_bc_driver) {
 778                 ret = -ENOMEM;
 779                 goto err_free_bcs;
 780         }
 781 
 782         ehv_bc_driver->driver_name = "ehv-bc";
 783         ehv_bc_driver->name = ehv_bc_console.name;
 784         ehv_bc_driver->type = TTY_DRIVER_TYPE_CONSOLE;
 785         ehv_bc_driver->subtype = SYSTEM_TYPE_CONSOLE;
 786         ehv_bc_driver->init_termios = tty_std_termios;
 787         ehv_bc_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
 788         tty_set_operations(ehv_bc_driver, &ehv_bc_ops);
 789 
 790         ret = tty_register_driver(ehv_bc_driver);
 791         if (ret) {
 792                 pr_err("ehv-bc: could not register tty driver (ret=%i)\n", ret);
 793                 goto err_put_tty_driver;
 794         }
 795 
 796         ret = platform_driver_register(&ehv_bc_tty_driver);
 797         if (ret) {
 798                 pr_err("ehv-bc: could not register platform driver (ret=%i)\n",
 799                        ret);
 800                 goto err_deregister_tty_driver;
 801         }
 802 
 803         return 0;
 804 
 805 err_deregister_tty_driver:
 806         tty_unregister_driver(ehv_bc_driver);
 807 err_put_tty_driver:
 808         put_tty_driver(ehv_bc_driver);
 809 err_free_bcs:
 810         kfree(bcs);
 811 
 812         return ret;
 813 }
 814 device_initcall(ehv_bc_init);