linux/drivers/tty/ehv_bytechan.c
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   1/* ePAPR hypervisor byte channel device driver
   2 *
   3 * Copyright 2009-2011 Freescale Semiconductor, Inc.
   4 *
   5 * Author: Timur Tabi <timur@freescale.com>
   6 *
   7 * This file is licensed under the terms of the GNU General Public License
   8 * version 2.  This program is licensed "as is" without any warranty of any
   9 * kind, whether express or implied.
  10 *
  11 * This driver support three distinct interfaces, all of which are related to
  12 * ePAPR hypervisor byte channels.
  13 *
  14 * 1) An early-console (udbg) driver.  This provides early console output
  15 * through a byte channel.  The byte channel handle must be specified in a
  16 * Kconfig option.
  17 *
  18 * 2) A normal console driver.  Output is sent to the byte channel designated
  19 * for stdout in the device tree.  The console driver is for handling kernel
  20 * printk calls.
  21 *
  22 * 3) A tty driver, which is used to handle user-space input and output.  The
  23 * byte channel used for the console is designated as the default tty.
  24 */
  25
  26#include <linux/module.h>
  27#include <linux/init.h>
  28#include <linux/slab.h>
  29#include <linux/err.h>
  30#include <linux/interrupt.h>
  31#include <linux/fs.h>
  32#include <linux/poll.h>
  33#include <asm/epapr_hcalls.h>
  34#include <linux/of.h>
  35#include <linux/platform_device.h>
  36#include <linux/cdev.h>
  37#include <linux/console.h>
  38#include <linux/tty.h>
  39#include <linux/tty_flip.h>
  40#include <linux/circ_buf.h>
  41#include <asm/udbg.h>
  42
  43/* The size of the transmit circular buffer.  This must be a power of two. */
  44#define BUF_SIZE        2048
  45
  46/* Per-byte channel private data */
  47struct ehv_bc_data {
  48        struct device *dev;
  49        struct tty_port port;
  50        uint32_t handle;
  51        unsigned int rx_irq;
  52        unsigned int tx_irq;
  53
  54        spinlock_t lock;        /* lock for transmit buffer */
  55        unsigned char buf[BUF_SIZE];    /* transmit circular buffer */
  56        unsigned int head;      /* circular buffer head */
  57        unsigned int tail;      /* circular buffer tail */
  58
  59        int tx_irq_enabled;     /* true == TX interrupt is enabled */
  60};
  61
  62/* Array of byte channel objects */
  63static struct ehv_bc_data *bcs;
  64
  65/* Byte channel handle for stdout (and stdin), taken from device tree */
  66static unsigned int stdout_bc;
  67
  68/* Virtual IRQ for the byte channel handle for stdin, taken from device tree */
  69static unsigned int stdout_irq;
  70
  71/**************************** SUPPORT FUNCTIONS ****************************/
  72
  73/*
  74 * Enable the transmit interrupt
  75 *
  76 * Unlike a serial device, byte channels have no mechanism for disabling their
  77 * own receive or transmit interrupts.  To emulate that feature, we toggle
  78 * the IRQ in the kernel.
  79 *
  80 * We cannot just blindly call enable_irq() or disable_irq(), because these
  81 * calls are reference counted.  This means that we cannot call enable_irq()
  82 * if interrupts are already enabled.  This can happen in two situations:
  83 *
  84 * 1. The tty layer makes two back-to-back calls to ehv_bc_tty_write()
  85 * 2. A transmit interrupt occurs while executing ehv_bc_tx_dequeue()
  86 *
  87 * To work around this, we keep a flag to tell us if the IRQ is enabled or not.
  88 */
  89static void enable_tx_interrupt(struct ehv_bc_data *bc)
  90{
  91        if (!bc->tx_irq_enabled) {
  92                enable_irq(bc->tx_irq);
  93                bc->tx_irq_enabled = 1;
  94        }
  95}
  96
  97static void disable_tx_interrupt(struct ehv_bc_data *bc)
  98{
  99        if (bc->tx_irq_enabled) {
 100                disable_irq_nosync(bc->tx_irq);
 101                bc->tx_irq_enabled = 0;
 102        }
 103}
 104
 105/*
 106 * find the byte channel handle to use for the console
 107 *
 108 * The byte channel to be used for the console is specified via a "stdout"
 109 * property in the /chosen node.
 110 *
 111 * For compatible with legacy device trees, we also look for a "stdout" alias.
 112 */
 113static int find_console_handle(void)
 114{
 115        struct device_node *np, *np2;
 116        const char *sprop = NULL;
 117        const uint32_t *iprop;
 118
 119        np = of_find_node_by_path("/chosen");
 120        if (np)
 121                sprop = of_get_property(np, "stdout-path", NULL);
 122
 123        if (!np || !sprop) {
 124                of_node_put(np);
 125                np = of_find_node_by_name(NULL, "aliases");
 126                if (np)
 127                        sprop = of_get_property(np, "stdout", NULL);
 128        }
 129
 130        if (!sprop) {
 131                of_node_put(np);
 132                return 0;
 133        }
 134
 135        /* We don't care what the aliased node is actually called.  We only
 136         * care if it's compatible with "epapr,hv-byte-channel", because that
 137         * indicates that it's a byte channel node.  We use a temporary
 138         * variable, 'np2', because we can't release 'np' until we're done with
 139         * 'sprop'.
 140         */
 141        np2 = of_find_node_by_path(sprop);
 142        of_node_put(np);
 143        np = np2;
 144        if (!np) {
 145                pr_warning("ehv-bc: stdout node '%s' does not exist\n", sprop);
 146                return 0;
 147        }
 148
 149        /* Is it a byte channel? */
 150        if (!of_device_is_compatible(np, "epapr,hv-byte-channel")) {
 151                of_node_put(np);
 152                return 0;
 153        }
 154
 155        stdout_irq = irq_of_parse_and_map(np, 0);
 156        if (stdout_irq == NO_IRQ) {
 157                pr_err("ehv-bc: no 'interrupts' property in %s node\n", sprop);
 158                of_node_put(np);
 159                return 0;
 160        }
 161
 162        /*
 163         * The 'hv-handle' property contains the handle for this byte channel.
 164         */
 165        iprop = of_get_property(np, "hv-handle", NULL);
 166        if (!iprop) {
 167                pr_err("ehv-bc: no 'hv-handle' property in %s node\n",
 168                       np->name);
 169                of_node_put(np);
 170                return 0;
 171        }
 172        stdout_bc = be32_to_cpu(*iprop);
 173
 174        of_node_put(np);
 175        return 1;
 176}
 177
 178/*************************** EARLY CONSOLE DRIVER ***************************/
 179
 180#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC
 181
 182/*
 183 * send a byte to a byte channel, wait if necessary
 184 *
 185 * This function sends a byte to a byte channel, and it waits and
 186 * retries if the byte channel is full.  It returns if the character
 187 * has been sent, or if some error has occurred.
 188 *
 189 */
 190static void byte_channel_spin_send(const char data)
 191{
 192        int ret, count;
 193
 194        do {
 195                count = 1;
 196                ret = ev_byte_channel_send(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
 197                                           &count, &data);
 198        } while (ret == EV_EAGAIN);
 199}
 200
 201/*
 202 * The udbg subsystem calls this function to display a single character.
 203 * We convert CR to a CR/LF.
 204 */
 205static void ehv_bc_udbg_putc(char c)
 206{
 207        if (c == '\n')
 208                byte_channel_spin_send('\r');
 209
 210        byte_channel_spin_send(c);
 211}
 212
 213/*
 214 * early console initialization
 215 *
 216 * PowerPC kernels support an early printk console, also known as udbg.
 217 * This function must be called via the ppc_md.init_early function pointer.
 218 * At this point, the device tree has been unflattened, so we can obtain the
 219 * byte channel handle for stdout.
 220 *
 221 * We only support displaying of characters (putc).  We do not support
 222 * keyboard input.
 223 */
 224void __init udbg_init_ehv_bc(void)
 225{
 226        unsigned int rx_count, tx_count;
 227        unsigned int ret;
 228
 229        /* Verify the byte channel handle */
 230        ret = ev_byte_channel_poll(CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE,
 231                                   &rx_count, &tx_count);
 232        if (ret)
 233                return;
 234
 235        udbg_putc = ehv_bc_udbg_putc;
 236        register_early_udbg_console();
 237
 238        udbg_printf("ehv-bc: early console using byte channel handle %u\n",
 239                    CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
 240}
 241
 242#endif
 243
 244/****************************** CONSOLE DRIVER ******************************/
 245
 246static struct tty_driver *ehv_bc_driver;
 247
 248/*
 249 * Byte channel console sending worker function.
 250 *
 251 * For consoles, if the output buffer is full, we should just spin until it
 252 * clears.
 253 */
 254static int ehv_bc_console_byte_channel_send(unsigned int handle, const char *s,
 255                             unsigned int count)
 256{
 257        unsigned int len;
 258        int ret = 0;
 259
 260        while (count) {
 261                len = min_t(unsigned int, count, EV_BYTE_CHANNEL_MAX_BYTES);
 262                do {
 263                        ret = ev_byte_channel_send(handle, &len, s);
 264                } while (ret == EV_EAGAIN);
 265                count -= len;
 266                s += len;
 267        }
 268
 269        return ret;
 270}
 271
 272/*
 273 * write a string to the console
 274 *
 275 * This function gets called to write a string from the kernel, typically from
 276 * a printk().  This function spins until all data is written.
 277 *
 278 * We copy the data to a temporary buffer because we need to insert a \r in
 279 * front of every \n.  It's more efficient to copy the data to the buffer than
 280 * it is to make multiple hcalls for each character or each newline.
 281 */
 282static void ehv_bc_console_write(struct console *co, const char *s,
 283                                 unsigned int count)
 284{
 285        char s2[EV_BYTE_CHANNEL_MAX_BYTES];
 286        unsigned int i, j = 0;
 287        char c;
 288
 289        for (i = 0; i < count; i++) {
 290                c = *s++;
 291
 292                if (c == '\n')
 293                        s2[j++] = '\r';
 294
 295                s2[j++] = c;
 296                if (j >= (EV_BYTE_CHANNEL_MAX_BYTES - 1)) {
 297                        if (ehv_bc_console_byte_channel_send(stdout_bc, s2, j))
 298                                return;
 299                        j = 0;
 300                }
 301        }
 302
 303        if (j)
 304                ehv_bc_console_byte_channel_send(stdout_bc, s2, j);
 305}
 306
 307/*
 308 * When /dev/console is opened, the kernel iterates the console list looking
 309 * for one with ->device and then calls that method. On success, it expects
 310 * the passed-in int* to contain the minor number to use.
 311 */
 312static struct tty_driver *ehv_bc_console_device(struct console *co, int *index)
 313{
 314        *index = co->index;
 315
 316        return ehv_bc_driver;
 317}
 318
 319static struct console ehv_bc_console = {
 320        .name           = "ttyEHV",
 321        .write          = ehv_bc_console_write,
 322        .device         = ehv_bc_console_device,
 323        .flags          = CON_PRINTBUFFER | CON_ENABLED,
 324};
 325
 326/*
 327 * Console initialization
 328 *
 329 * This is the first function that is called after the device tree is
 330 * available, so here is where we determine the byte channel handle and IRQ for
 331 * stdout/stdin, even though that information is used by the tty and character
 332 * drivers.
 333 */
 334static int __init ehv_bc_console_init(void)
 335{
 336        if (!find_console_handle()) {
 337                pr_debug("ehv-bc: stdout is not a byte channel\n");
 338                return -ENODEV;
 339        }
 340
 341#ifdef CONFIG_PPC_EARLY_DEBUG_EHV_BC
 342        /* Print a friendly warning if the user chose the wrong byte channel
 343         * handle for udbg.
 344         */
 345        if (stdout_bc != CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE)
 346                pr_warning("ehv-bc: udbg handle %u is not the stdout handle\n",
 347                           CONFIG_PPC_EARLY_DEBUG_EHV_BC_HANDLE);
 348#endif
 349
 350        /* add_preferred_console() must be called before register_console(),
 351           otherwise it won't work.  However, we don't want to enumerate all the
 352           byte channels here, either, since we only care about one. */
 353
 354        add_preferred_console(ehv_bc_console.name, ehv_bc_console.index, NULL);
 355        register_console(&ehv_bc_console);
 356
 357        pr_info("ehv-bc: registered console driver for byte channel %u\n",
 358                stdout_bc);
 359
 360        return 0;
 361}
 362console_initcall(ehv_bc_console_init);
 363
 364/******************************** TTY DRIVER ********************************/
 365
 366/*
 367 * byte channel receive interupt handler
 368 *
 369 * This ISR is called whenever data is available on a byte channel.
 370 */
 371static irqreturn_t ehv_bc_tty_rx_isr(int irq, void *data)
 372{
 373        struct ehv_bc_data *bc = data;
 374        struct tty_struct *ttys = tty_port_tty_get(&bc->port);
 375        unsigned int rx_count, tx_count, len;
 376        int count;
 377        char buffer[EV_BYTE_CHANNEL_MAX_BYTES];
 378        int ret;
 379
 380        /* ttys could be NULL during a hangup */
 381        if (!ttys)
 382                return IRQ_HANDLED;
 383
 384        /* Find out how much data needs to be read, and then ask the TTY layer
 385         * if it can handle that much.  We want to ensure that every byte we
 386         * read from the byte channel will be accepted by the TTY layer.
 387         */
 388        ev_byte_channel_poll(bc->handle, &rx_count, &tx_count);
 389        count = tty_buffer_request_room(ttys, rx_count);
 390
 391        /* 'count' is the maximum amount of data the TTY layer can accept at
 392         * this time.  However, during testing, I was never able to get 'count'
 393         * to be less than 'rx_count'.  I'm not sure whether I'm calling it
 394         * correctly.
 395         */
 396
 397        while (count > 0) {
 398                len = min_t(unsigned int, count, sizeof(buffer));
 399
 400                /* Read some data from the byte channel.  This function will
 401                 * never return more than EV_BYTE_CHANNEL_MAX_BYTES bytes.
 402                 */
 403                ev_byte_channel_receive(bc->handle, &len, buffer);
 404
 405                /* 'len' is now the amount of data that's been received. 'len'
 406                 * can't be zero, and most likely it's equal to one.
 407                 */
 408
 409                /* Pass the received data to the tty layer. */
 410                ret = tty_insert_flip_string(ttys, buffer, len);
 411
 412                /* 'ret' is the number of bytes that the TTY layer accepted.
 413                 * If it's not equal to 'len', then it means the buffer is
 414                 * full, which should never happen.  If it does happen, we can
 415                 * exit gracefully, but we drop the last 'len - ret' characters
 416                 * that we read from the byte channel.
 417                 */
 418                if (ret != len)
 419                        break;
 420
 421                count -= len;
 422        }
 423
 424        /* Tell the tty layer that we're done. */
 425        tty_flip_buffer_push(ttys);
 426
 427        tty_kref_put(ttys);
 428
 429        return IRQ_HANDLED;
 430}
 431
 432/*
 433 * dequeue the transmit buffer to the hypervisor
 434 *
 435 * This function, which can be called in interrupt context, dequeues as much
 436 * data as possible from the transmit buffer to the byte channel.
 437 */
 438static void ehv_bc_tx_dequeue(struct ehv_bc_data *bc)
 439{
 440        unsigned int count;
 441        unsigned int len, ret;
 442        unsigned long flags;
 443
 444        do {
 445                spin_lock_irqsave(&bc->lock, flags);
 446                len = min_t(unsigned int,
 447                            CIRC_CNT_TO_END(bc->head, bc->tail, BUF_SIZE),
 448                            EV_BYTE_CHANNEL_MAX_BYTES);
 449
 450                ret = ev_byte_channel_send(bc->handle, &len, bc->buf + bc->tail);
 451
 452                /* 'len' is valid only if the return code is 0 or EV_EAGAIN */
 453                if (!ret || (ret == EV_EAGAIN))
 454                        bc->tail = (bc->tail + len) & (BUF_SIZE - 1);
 455
 456                count = CIRC_CNT(bc->head, bc->tail, BUF_SIZE);
 457                spin_unlock_irqrestore(&bc->lock, flags);
 458        } while (count && !ret);
 459
 460        spin_lock_irqsave(&bc->lock, flags);
 461        if (CIRC_CNT(bc->head, bc->tail, BUF_SIZE))
 462                /*
 463                 * If we haven't emptied the buffer, then enable the TX IRQ.
 464                 * We'll get an interrupt when there's more room in the
 465                 * hypervisor's output buffer.
 466                 */
 467                enable_tx_interrupt(bc);
 468        else
 469                disable_tx_interrupt(bc);
 470        spin_unlock_irqrestore(&bc->lock, flags);
 471}
 472
 473/*
 474 * byte channel transmit interupt handler
 475 *
 476 * This ISR is called whenever space becomes available for transmitting
 477 * characters on a byte channel.
 478 */
 479static irqreturn_t ehv_bc_tty_tx_isr(int irq, void *data)
 480{
 481        struct ehv_bc_data *bc = data;
 482        struct tty_struct *ttys = tty_port_tty_get(&bc->port);
 483
 484        ehv_bc_tx_dequeue(bc);
 485        if (ttys) {
 486                tty_wakeup(ttys);
 487                tty_kref_put(ttys);
 488        }
 489
 490        return IRQ_HANDLED;
 491}
 492
 493/*
 494 * This function is called when the tty layer has data for us send.  We store
 495 * the data first in a circular buffer, and then dequeue as much of that data
 496 * as possible.
 497 *
 498 * We don't need to worry about whether there is enough room in the buffer for
 499 * all the data.  The purpose of ehv_bc_tty_write_room() is to tell the tty
 500 * layer how much data it can safely send to us.  We guarantee that
 501 * ehv_bc_tty_write_room() will never lie, so the tty layer will never send us
 502 * too much data.
 503 */
 504static int ehv_bc_tty_write(struct tty_struct *ttys, const unsigned char *s,
 505                            int count)
 506{
 507        struct ehv_bc_data *bc = ttys->driver_data;
 508        unsigned long flags;
 509        unsigned int len;
 510        unsigned int written = 0;
 511
 512        while (1) {
 513                spin_lock_irqsave(&bc->lock, flags);
 514                len = CIRC_SPACE_TO_END(bc->head, bc->tail, BUF_SIZE);
 515                if (count < len)
 516                        len = count;
 517                if (len) {
 518                        memcpy(bc->buf + bc->head, s, len);
 519                        bc->head = (bc->head + len) & (BUF_SIZE - 1);
 520                }
 521                spin_unlock_irqrestore(&bc->lock, flags);
 522                if (!len)
 523                        break;
 524
 525                s += len;
 526                count -= len;
 527                written += len;
 528        }
 529
 530        ehv_bc_tx_dequeue(bc);
 531
 532        return written;
 533}
 534
 535/*
 536 * This function can be called multiple times for a given tty_struct, which is
 537 * why we initialize bc->ttys in ehv_bc_tty_port_activate() instead.
 538 *
 539 * The tty layer will still call this function even if the device was not
 540 * registered (i.e. tty_register_device() was not called).  This happens
 541 * because tty_register_device() is optional and some legacy drivers don't
 542 * use it.  So we need to check for that.
 543 */
 544static int ehv_bc_tty_open(struct tty_struct *ttys, struct file *filp)
 545{
 546        struct ehv_bc_data *bc = &bcs[ttys->index];
 547
 548        if (!bc->dev)
 549                return -ENODEV;
 550
 551        return tty_port_open(&bc->port, ttys, filp);
 552}
 553
 554/*
 555 * Amazingly, if ehv_bc_tty_open() returns an error code, the tty layer will
 556 * still call this function to close the tty device.  So we can't assume that
 557 * the tty port has been initialized.
 558 */
 559static void ehv_bc_tty_close(struct tty_struct *ttys, struct file *filp)
 560{
 561        struct ehv_bc_data *bc = &bcs[ttys->index];
 562
 563        if (bc->dev)
 564                tty_port_close(&bc->port, ttys, filp);
 565}
 566
 567/*
 568 * Return the amount of space in the output buffer
 569 *
 570 * This is actually a contract between the driver and the tty layer outlining
 571 * how much write room the driver can guarantee will be sent OR BUFFERED.  This
 572 * driver MUST honor the return value.
 573 */
 574static int ehv_bc_tty_write_room(struct tty_struct *ttys)
 575{
 576        struct ehv_bc_data *bc = ttys->driver_data;
 577        unsigned long flags;
 578        int count;
 579
 580        spin_lock_irqsave(&bc->lock, flags);
 581        count = CIRC_SPACE(bc->head, bc->tail, BUF_SIZE);
 582        spin_unlock_irqrestore(&bc->lock, flags);
 583
 584        return count;
 585}
 586
 587/*
 588 * Stop sending data to the tty layer
 589 *
 590 * This function is called when the tty layer's input buffers are getting full,
 591 * so the driver should stop sending it data.  The easiest way to do this is to
 592 * disable the RX IRQ, which will prevent ehv_bc_tty_rx_isr() from being
 593 * called.
 594 *
 595 * The hypervisor will continue to queue up any incoming data.  If there is any
 596 * data in the queue when the RX interrupt is enabled, we'll immediately get an
 597 * RX interrupt.
 598 */
 599static void ehv_bc_tty_throttle(struct tty_struct *ttys)
 600{
 601        struct ehv_bc_data *bc = ttys->driver_data;
 602
 603        disable_irq(bc->rx_irq);
 604}
 605
 606/*
 607 * Resume sending data to the tty layer
 608 *
 609 * This function is called after previously calling ehv_bc_tty_throttle().  The
 610 * tty layer's input buffers now have more room, so the driver can resume
 611 * sending it data.
 612 */
 613static void ehv_bc_tty_unthrottle(struct tty_struct *ttys)
 614{
 615        struct ehv_bc_data *bc = ttys->driver_data;
 616
 617        /* If there is any data in the queue when the RX interrupt is enabled,
 618         * we'll immediately get an RX interrupt.
 619         */
 620        enable_irq(bc->rx_irq);
 621}
 622
 623static void ehv_bc_tty_hangup(struct tty_struct *ttys)
 624{
 625        struct ehv_bc_data *bc = ttys->driver_data;
 626
 627        ehv_bc_tx_dequeue(bc);
 628        tty_port_hangup(&bc->port);
 629}
 630
 631/*
 632 * TTY driver operations
 633 *
 634 * If we could ask the hypervisor how much data is still in the TX buffer, or
 635 * at least how big the TX buffers are, then we could implement the
 636 * .wait_until_sent and .chars_in_buffer functions.
 637 */
 638static const struct tty_operations ehv_bc_ops = {
 639        .open           = ehv_bc_tty_open,
 640        .close          = ehv_bc_tty_close,
 641        .write          = ehv_bc_tty_write,
 642        .write_room     = ehv_bc_tty_write_room,
 643        .throttle       = ehv_bc_tty_throttle,
 644        .unthrottle     = ehv_bc_tty_unthrottle,
 645        .hangup         = ehv_bc_tty_hangup,
 646};
 647
 648/*
 649 * initialize the TTY port
 650 *
 651 * This function will only be called once, no matter how many times
 652 * ehv_bc_tty_open() is called.  That's why we register the ISR here, and also
 653 * why we initialize tty_struct-related variables here.
 654 */
 655static int ehv_bc_tty_port_activate(struct tty_port *port,
 656                                    struct tty_struct *ttys)
 657{
 658        struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);
 659        int ret;
 660
 661        ttys->driver_data = bc;
 662
 663        ret = request_irq(bc->rx_irq, ehv_bc_tty_rx_isr, 0, "ehv-bc", bc);
 664        if (ret < 0) {
 665                dev_err(bc->dev, "could not request rx irq %u (ret=%i)\n",
 666                       bc->rx_irq, ret);
 667                return ret;
 668        }
 669
 670        /* request_irq also enables the IRQ */
 671        bc->tx_irq_enabled = 1;
 672
 673        ret = request_irq(bc->tx_irq, ehv_bc_tty_tx_isr, 0, "ehv-bc", bc);
 674        if (ret < 0) {
 675                dev_err(bc->dev, "could not request tx irq %u (ret=%i)\n",
 676                       bc->tx_irq, ret);
 677                free_irq(bc->rx_irq, bc);
 678                return ret;
 679        }
 680
 681        /* The TX IRQ is enabled only when we can't write all the data to the
 682         * byte channel at once, so by default it's disabled.
 683         */
 684        disable_tx_interrupt(bc);
 685
 686        return 0;
 687}
 688
 689static void ehv_bc_tty_port_shutdown(struct tty_port *port)
 690{
 691        struct ehv_bc_data *bc = container_of(port, struct ehv_bc_data, port);
 692
 693        free_irq(bc->tx_irq, bc);
 694        free_irq(bc->rx_irq, bc);
 695}
 696
 697static const struct tty_port_operations ehv_bc_tty_port_ops = {
 698        .activate = ehv_bc_tty_port_activate,
 699        .shutdown = ehv_bc_tty_port_shutdown,
 700};
 701
 702static int __devinit ehv_bc_tty_probe(struct platform_device *pdev)
 703{
 704        struct device_node *np = pdev->dev.of_node;
 705        struct ehv_bc_data *bc;
 706        const uint32_t *iprop;
 707        unsigned int handle;
 708        int ret;
 709        static unsigned int index = 1;
 710        unsigned int i;
 711
 712        iprop = of_get_property(np, "hv-handle", NULL);
 713        if (!iprop) {
 714                dev_err(&pdev->dev, "no 'hv-handle' property in %s node\n",
 715                        np->name);
 716                return -ENODEV;
 717        }
 718
 719        /* We already told the console layer that the index for the console
 720         * device is zero, so we need to make sure that we use that index when
 721         * we probe the console byte channel node.
 722         */
 723        handle = be32_to_cpu(*iprop);
 724        i = (handle == stdout_bc) ? 0 : index++;
 725        bc = &bcs[i];
 726
 727        bc->handle = handle;
 728        bc->head = 0;
 729        bc->tail = 0;
 730        spin_lock_init(&bc->lock);
 731
 732        bc->rx_irq = irq_of_parse_and_map(np, 0);
 733        bc->tx_irq = irq_of_parse_and_map(np, 1);
 734        if ((bc->rx_irq == NO_IRQ) || (bc->tx_irq == NO_IRQ)) {
 735                dev_err(&pdev->dev, "no 'interrupts' property in %s node\n",
 736                        np->name);
 737                ret = -ENODEV;
 738                goto error;
 739        }
 740
 741        bc->dev = tty_register_device(ehv_bc_driver, i, &pdev->dev);
 742        if (IS_ERR(bc->dev)) {
 743                ret = PTR_ERR(bc->dev);
 744                dev_err(&pdev->dev, "could not register tty (ret=%i)\n", ret);
 745                goto error;
 746        }
 747
 748        tty_port_init(&bc->port);
 749        bc->port.ops = &ehv_bc_tty_port_ops;
 750
 751        dev_set_drvdata(&pdev->dev, bc);
 752
 753        dev_info(&pdev->dev, "registered /dev/%s%u for byte channel %u\n",
 754                ehv_bc_driver->name, i, bc->handle);
 755
 756        return 0;
 757
 758error:
 759        irq_dispose_mapping(bc->tx_irq);
 760        irq_dispose_mapping(bc->rx_irq);
 761
 762        memset(bc, 0, sizeof(struct ehv_bc_data));
 763        return ret;
 764}
 765
 766static int ehv_bc_tty_remove(struct platform_device *pdev)
 767{
 768        struct ehv_bc_data *bc = dev_get_drvdata(&pdev->dev);
 769
 770        tty_unregister_device(ehv_bc_driver, bc - bcs);
 771
 772        irq_dispose_mapping(bc->tx_irq);
 773        irq_dispose_mapping(bc->rx_irq);
 774
 775        return 0;
 776}
 777
 778static const struct of_device_id ehv_bc_tty_of_ids[] = {
 779        { .compatible = "epapr,hv-byte-channel" },
 780        {}
 781};
 782
 783static struct platform_driver ehv_bc_tty_driver = {
 784        .driver = {
 785                .owner = THIS_MODULE,
 786                .name = "ehv-bc",
 787                .of_match_table = ehv_bc_tty_of_ids,
 788        },
 789        .probe          = ehv_bc_tty_probe,
 790        .remove         = ehv_bc_tty_remove,
 791};
 792
 793/**
 794 * ehv_bc_init - ePAPR hypervisor byte channel driver initialization
 795 *
 796 * This function is called when this module is loaded.
 797 */
 798static int __init ehv_bc_init(void)
 799{
 800        struct device_node *np;
 801        unsigned int count = 0; /* Number of elements in bcs[] */
 802        int ret;
 803
 804        pr_info("ePAPR hypervisor byte channel driver\n");
 805
 806        /* Count the number of byte channels */
 807        for_each_compatible_node(np, NULL, "epapr,hv-byte-channel")
 808                count++;
 809
 810        if (!count)
 811                return -ENODEV;
 812
 813        /* The array index of an element in bcs[] is the same as the tty index
 814         * for that element.  If you know the address of an element in the
 815         * array, then you can use pointer math (e.g. "bc - bcs") to get its
 816         * tty index.
 817         */
 818        bcs = kzalloc(count * sizeof(struct ehv_bc_data), GFP_KERNEL);
 819        if (!bcs)
 820                return -ENOMEM;
 821
 822        ehv_bc_driver = alloc_tty_driver(count);
 823        if (!ehv_bc_driver) {
 824                ret = -ENOMEM;
 825                goto error;
 826        }
 827
 828        ehv_bc_driver->driver_name = "ehv-bc";
 829        ehv_bc_driver->name = ehv_bc_console.name;
 830        ehv_bc_driver->type = TTY_DRIVER_TYPE_CONSOLE;
 831        ehv_bc_driver->subtype = SYSTEM_TYPE_CONSOLE;
 832        ehv_bc_driver->init_termios = tty_std_termios;
 833        ehv_bc_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
 834        tty_set_operations(ehv_bc_driver, &ehv_bc_ops);
 835
 836        ret = tty_register_driver(ehv_bc_driver);
 837        if (ret) {
 838                pr_err("ehv-bc: could not register tty driver (ret=%i)\n", ret);
 839                goto error;
 840        }
 841
 842        ret = platform_driver_register(&ehv_bc_tty_driver);
 843        if (ret) {
 844                pr_err("ehv-bc: could not register platform driver (ret=%i)\n",
 845                       ret);
 846                goto error;
 847        }
 848
 849        return 0;
 850
 851error:
 852        if (ehv_bc_driver) {
 853                tty_unregister_driver(ehv_bc_driver);
 854                put_tty_driver(ehv_bc_driver);
 855        }
 856
 857        kfree(bcs);
 858
 859        return ret;
 860}
 861
 862
 863/**
 864 * ehv_bc_exit - ePAPR hypervisor byte channel driver termination
 865 *
 866 * This function is called when this driver is unloaded.
 867 */
 868static void __exit ehv_bc_exit(void)
 869{
 870        tty_unregister_driver(ehv_bc_driver);
 871        put_tty_driver(ehv_bc_driver);
 872        kfree(bcs);
 873}
 874
 875module_init(ehv_bc_init);
 876module_exit(ehv_bc_exit);
 877
 878MODULE_AUTHOR("Timur Tabi <timur@freescale.com>");
 879MODULE_DESCRIPTION("ePAPR hypervisor byte channel driver");
 880MODULE_LICENSE("GPL v2");
 881
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