hvsi.c

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/*
 * Copyright (C) 2004 Hollis Blanchard <[email protected]>, IBM
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
 */

/* Host Virtual Serial Interface (HVSI) is a protocol between the hosted OS
 * and the service processor on IBM pSeries servers. On these servers, there
 * are no serial ports under the OS's control, and sometimes there is no other
 * console available either. However, the service processor has two standard
 * serial ports, so this over-complicated protocol allows the OS to control
 * those ports by proxy.
 *
 * Besides data, the procotol supports the reading/writing of the serial
 * port's DTR line, and the reading of the CD line. This is to allow the OS to
 * control a modem attached to the service processor's serial port. Note that
 * the OS cannot change the speed of the port through this protocol.
 */

#undef DEBUG

#include <linux/console.h>
#include <linux/ctype.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/major.h>
#include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/sysrq.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <asm/hvcall.h>
#include <asm/hvconsole.h>
#include <asm/prom.h>
#include <asm/uaccess.h>
#include <asm/vio.h>
#include <asm/param.h>
#include <asm/hvsi.h>

#define HVSI_MAJOR  229
#define HVSI_MINOR  128
#define MAX_NR_HVSI_CONSOLES 4

#define HVSI_TIMEOUT (5*HZ)
#define HVSI_VERSION 1
#define HVSI_MAX_PACKET 256
#define HVSI_MAX_READ 16
#define HVSI_MAX_OUTGOING_DATA 12
#define N_OUTBUF 12

/*
 * we pass data via two 8-byte registers, so we would like our char arrays
 * properly aligned for those loads.
 */
#define __ALIGNED__ __attribute__((__aligned__(sizeof(long))))

struct hvsi_struct {
    struct tty_port port;
    struct delayed_work writer;
    struct work_struct handshaker;
    wait_queue_head_t emptyq; /* woken when outbuf is emptied */
    wait_queue_head_t stateq; /* woken when HVSI state changes */
    spinlock_t lock;
    int index;
    uint8_t throttle_buf[128];
    uint8_t outbuf[N_OUTBUF]; /* to implement write_room and chars_in_buffer */
    /* inbuf is for packet reassembly. leave a little room for leftovers. */
    uint8_t inbuf[HVSI_MAX_PACKET + HVSI_MAX_READ];
    uint8_t *inbuf_end;
    int n_throttle;
    int n_outbuf;
    uint32_t vtermno;
    uint32_t virq;
    atomic_t seqno; /* HVSI packet sequence number */
    uint16_t mctrl;
    uint8_t state;  /* HVSI protocol state */
    uint8_t flags;
#ifdef CONFIG_MAGIC_SYSRQ
    uint8_t sysrq;
#endif /* CONFIG_MAGIC_SYSRQ */
};
static struct hvsi_struct hvsi_ports[MAX_NR_HVSI_CONSOLES];

static struct tty_driver *hvsi_driver;
static int hvsi_count;
static int (*hvsi_wait)(struct hvsi_struct *hp, int state);

enum HVSI_PROTOCOL_STATE {
    HVSI_CLOSED,
    HVSI_WAIT_FOR_VER_RESPONSE,
    HVSI_WAIT_FOR_VER_QUERY,
    HVSI_OPEN,
    HVSI_WAIT_FOR_MCTRL_RESPONSE,
    HVSI_FSP_DIED,
};
#define HVSI_CONSOLE 0x1

static inline int is_console(struct hvsi_struct *hp)
{
    return hp->flags & HVSI_CONSOLE;
}

static inline int is_open(struct hvsi_struct *hp)
{
    /* if we're waiting for an mctrl then we're already open */
    return (hp->state == HVSI_OPEN)
            || (hp->state == HVSI_WAIT_FOR_MCTRL_RESPONSE);
}

static inline void print_state(struct hvsi_struct *hp)
{
#ifdef DEBUG
    static const char *state_names[] = {
        "HVSI_CLOSED",
        "HVSI_WAIT_FOR_VER_RESPONSE",
        "HVSI_WAIT_FOR_VER_QUERY",
        "HVSI_OPEN",
        "HVSI_WAIT_FOR_MCTRL_RESPONSE",
        "HVSI_FSP_DIED",
    };
    const char *name = (hp->state < ARRAY_SIZE(state_names))
        ? state_names[hp->state] : "UNKNOWN";

    pr_debug("hvsi%i: state = %s\n", hp->index, name);
#endif /* DEBUG */
}

static inline void __set_state(struct hvsi_struct *hp, int state)
{
    hp->state = state;
    print_state(hp);
    wake_up_all(&hp->stateq);
}

static inline void set_state(struct hvsi_struct *hp, int state)
{
    unsigned long flags;

    spin_lock_irqsave(&hp->lock, flags);
    __set_state(hp, state);
    spin_unlock_irqrestore(&hp->lock, flags);
}

static inline int len_packet(const uint8_t *packet)
{
    return (int)((struct hvsi_header *)packet)->len;
}

static inline int is_header(const uint8_t *packet)
{
    struct hvsi_header *header = (struct hvsi_header *)packet;
    return header->type >= VS_QUERY_RESPONSE_PACKET_HEADER;
}

static inline int got_packet(const struct hvsi_struct *hp, uint8_t *packet)
{
    if (hp->inbuf_end < packet + sizeof(struct hvsi_header))
        return 0; /* don't even have the packet header */

    if (hp->inbuf_end < (packet + len_packet(packet)))
        return 0; /* don't have the rest of the packet */

    return 1;
}

/* shift remaining bytes in packetbuf down */
static void compact_inbuf(struct hvsi_struct *hp, uint8_t *read_to)
{
    int remaining = (int)(hp->inbuf_end - read_to);

    pr_debug("%s: %i chars remain\n", __func__, remaining);

    if (read_to != hp->inbuf)
        memmove(hp->inbuf, read_to, remaining);

    hp->inbuf_end = hp->inbuf + remaining;
}

#ifdef DEBUG
#define dbg_dump_packet(packet) dump_packet(packet)
#define dbg_dump_hex(data, len) dump_hex(data, len)
#else
#define dbg_dump_packet(packet) do { } while (0)
#define dbg_dump_hex(data, len) do { } while (0)
#endif

static void dump_hex(const uint8_t *data, int len)
{
    int i;

    printk("    ");
    for (i=0; i < len; i++)
        printk("%.2x", data[i]);

    printk("\n    ");
    for (i=0; i < len; i++) {
        if (isprint(data[i]))
            printk("%c", data[i]);
        else
            printk(".");
    }
    printk("\n");
}

static void dump_packet(uint8_t *packet)
{
    struct hvsi_header *header = (struct hvsi_header *)packet;

    printk("type 0x%x, len %i, seqno %i:\n", header->type, header->len,
            header->seqno);

    dump_hex(packet, header->len);
}

static int hvsi_read(struct hvsi_struct *hp, char *buf, int count)
{
    unsigned long got;

    got = hvc_get_chars(hp->vtermno, buf, count);

    return got;
}

static void hvsi_recv_control(struct hvsi_struct *hp, uint8_t *packet,
    struct tty_struct *tty, struct hvsi_struct **to_handshake)
{
    struct hvsi_control *header = (struct hvsi_control *)packet;

    switch (header->verb) {
        case VSV_MODEM_CTL_UPDATE:
            if ((header->word & HVSI_TSCD) == 0) {
                /* CD went away; no more connection */
                pr_debug("hvsi%i: CD dropped\n", hp->index);
                hp->mctrl &= TIOCM_CD;
                if (tty && !C_CLOCAL(tty))
                    tty_hangup(tty);
            }
            break;
        case VSV_CLOSE_PROTOCOL:
            pr_debug("hvsi%i: service processor came back\n", hp->index);
            if (hp->state != HVSI_CLOSED) {
                *to_handshake = hp;
            }
            break;
        default:
            printk(KERN_WARNING "hvsi%i: unknown HVSI control packet: ",
                hp->index);
            dump_packet(packet);
            break;
    }
}

static void hvsi_recv_response(struct hvsi_struct *hp, uint8_t *packet)
{
    struct hvsi_query_response *resp = (struct hvsi_query_response *)packet;

    switch (hp->state) {
        case HVSI_WAIT_FOR_VER_RESPONSE:
            __set_state(hp, HVSI_WAIT_FOR_VER_QUERY);
            break;
        case HVSI_WAIT_FOR_MCTRL_RESPONSE:
            hp->mctrl = 0;
            if (resp->u.mctrl_word & HVSI_TSDTR)
                hp->mctrl |= TIOCM_DTR;
            if (resp->u.mctrl_word & HVSI_TSCD)
                hp->mctrl |= TIOCM_CD;
            __set_state(hp, HVSI_OPEN);
            break;
        default:
            printk(KERN_ERR "hvsi%i: unexpected query response: ", hp->index);
            dump_packet(packet);
            break;
    }
}

/* respond to service processor's version query */
static int hvsi_version_respond(struct hvsi_struct *hp, uint16_t query_seqno)
{
    struct hvsi_query_response packet __ALIGNED__;
    int wrote;

    packet.hdr.type = VS_QUERY_RESPONSE_PACKET_HEADER;
    packet.hdr.len = sizeof(struct hvsi_query_response);
    packet.hdr.seqno = atomic_inc_return(&hp->seqno);
    packet.verb = VSV_SEND_VERSION_NUMBER;
    packet.u.version = HVSI_VERSION;
    packet.query_seqno = query_seqno+1;

    pr_debug("%s: sending %i bytes\n", __func__, packet.hdr.len);
    dbg_dump_hex((uint8_t*)&packet, packet.hdr.len);

    wrote = hvc_put_chars(hp->vtermno, (char *)&packet, packet.hdr.len);
    if (wrote != packet.hdr.len) {
        printk(KERN_ERR "hvsi%i: couldn't send query response!\n",
            hp->index);
        return -EIO;
    }

    return 0;
}

static void hvsi_recv_query(struct hvsi_struct *hp, uint8_t *packet)
{
    struct hvsi_query *query = (struct hvsi_query *)packet;

    switch (hp->state) {
        case HVSI_WAIT_FOR_VER_QUERY:
            hvsi_version_respond(hp, query->hdr.seqno);
            __set_state(hp, HVSI_OPEN);
            break;
        default:
            printk(KERN_ERR "hvsi%i: unexpected query: ", hp->index);
            dump_packet(packet);
            break;
    }
}

static void hvsi_insert_chars(struct hvsi_struct *hp, struct tty_struct *tty,
        const char *buf, int len)
{
    int i;

    for (i=0; i < len; i++) {
        char c = buf[i];
#ifdef CONFIG_MAGIC_SYSRQ
        if (c == '\0') {
            hp->sysrq = 1;
            continue;
        } else if (hp->sysrq) {
            handle_sysrq(c);
            hp->sysrq = 0;
            continue;
        }
#endif /* CONFIG_MAGIC_SYSRQ */
        tty_insert_flip_char(tty, c, 0);
    }
}

/*
 * We could get 252 bytes of data at once here. But the tty layer only
 * throttles us at TTY_THRESHOLD_THROTTLE (128) bytes, so we could overflow
 * it. Accordingly we won't send more than 128 bytes at a time to the flip
 * buffer, which will give the tty buffer a chance to throttle us. Should the
 * value of TTY_THRESHOLD_THROTTLE change in n_tty.c, this code should be
 * revisited.
 */
#define TTY_THRESHOLD_THROTTLE 128
static bool hvsi_recv_data(struct hvsi_struct *hp, struct tty_struct *tty,
        const uint8_t *packet)
{
    const struct hvsi_header *header = (const struct hvsi_header *)packet;
    const uint8_t *data = packet + sizeof(struct hvsi_header);
    int datalen = header->len - sizeof(struct hvsi_header);
    int overflow = datalen - TTY_THRESHOLD_THROTTLE;

    pr_debug("queueing %i chars '%.*s'\n", datalen, datalen, data);

    if (datalen == 0)
        return false;

    if (overflow > 0) {
        pr_debug("%s: got >TTY_THRESHOLD_THROTTLE bytes\n", __func__);
        datalen = TTY_THRESHOLD_THROTTLE;
    }

    hvsi_insert_chars(hp, tty, data, datalen);

    if (overflow > 0) {
        /*
         * we still have more data to deliver, so we need to save off the
         * overflow and send it later
         */
        pr_debug("%s: deferring overflow\n", __func__);
        memcpy(hp->throttle_buf, data + TTY_THRESHOLD_THROTTLE, overflow);
        hp->n_throttle = overflow;
    }

    return true;
}

/*
 * Returns true/false indicating data successfully read from hypervisor.
 * Used both to get packets for tty connections and to advance the state
 * machine during console handshaking (in which case tty = NULL and we ignore
 * incoming data).
 */
static int hvsi_load_chunk(struct hvsi_struct *hp, struct tty_struct *tty,
        struct hvsi_struct **handshake)
{
    uint8_t *packet = hp->inbuf;
    int chunklen;
    bool flip = false;

    *handshake = NULL;

    chunklen = hvsi_read(hp, hp->inbuf_end, HVSI_MAX_READ);
    if (chunklen == 0) {
        pr_debug("%s: 0-length read\n", __func__);
        return 0;
    }

    pr_debug("%s: got %i bytes\n", __func__, chunklen);
    dbg_dump_hex(hp->inbuf_end, chunklen);

    hp->inbuf_end += chunklen;

    /* handle all completed packets */
    while ((packet < hp->inbuf_end) && got_packet(hp, packet)) {
        struct hvsi_header *header = (struct hvsi_header *)packet;

        if (!is_header(packet)) {
            printk(KERN_ERR "hvsi%i: got malformed packet\n", hp->index);
            /* skip bytes until we find a header or run out of data */
            while ((packet < hp->inbuf_end) && (!is_header(packet)))
                packet++;
            continue;
        }

        pr_debug("%s: handling %i-byte packet\n", __func__,
                len_packet(packet));
        dbg_dump_packet(packet);

        switch (header->type) {
            case VS_DATA_PACKET_HEADER:
                if (!is_open(hp))
                    break;
                if (tty == NULL)
                    break; /* no tty buffer to put data in */
                flip = hvsi_recv_data(hp, tty, packet);
                break;
            case VS_CONTROL_PACKET_HEADER:
                hvsi_recv_control(hp, packet, tty, handshake);
                break;
            case VS_QUERY_RESPONSE_PACKET_HEADER:
                hvsi_recv_response(hp, packet);
                break;
            case VS_QUERY_PACKET_HEADER:
                hvsi_recv_query(hp, packet);
                break;
            default:
                printk(KERN_ERR "hvsi%i: unknown HVSI packet type 0x%x\n",
                        hp->index, header->type);
                dump_packet(packet);
                break;
        }

        packet += len_packet(packet);

        if (*handshake) {
            pr_debug("%s: handshake\n", __func__);
            break;
        }
    }

    compact_inbuf(hp, packet);

    if (flip)
        tty_flip_buffer_push(tty);

    return 1;
}

static void hvsi_send_overflow(struct hvsi_struct *hp, struct tty_struct *tty)
{
    pr_debug("%s: delivering %i bytes overflow\n", __func__,
            hp->n_throttle);

    hvsi_insert_chars(hp, tty, hp->throttle_buf, hp->n_throttle);
    hp->n_throttle = 0;
}

/*
 * must get all pending data because we only get an irq on empty->non-empty
 * transition
 */
static irqreturn_t hvsi_interrupt(int irq, void *arg)
{
    struct hvsi_struct *hp = (struct hvsi_struct *)arg;
    struct hvsi_struct *handshake;
    struct tty_struct *tty;
    unsigned long flags;
    int again = 1;

    pr_debug("%s\n", __func__);

    tty = tty_port_tty_get(&hp->port);

    while (again) {
        spin_lock_irqsave(&hp->lock, flags);
        again = hvsi_load_chunk(hp, tty, &handshake);
        spin_unlock_irqrestore(&hp->lock, flags);

        if (handshake) {
            pr_debug("hvsi%i: attempting re-handshake\n", handshake->index);
            schedule_work(&handshake->handshaker);
        }
    }

    spin_lock_irqsave(&hp->lock, flags);
    if (tty && hp->n_throttle && !test_bit(TTY_THROTTLED, &tty->flags)) {
        /* we weren't hung up and we weren't throttled, so we can
         * deliver the rest now */
        hvsi_send_overflow(hp, tty);
        tty_flip_buffer_push(tty);
    }
    spin_unlock_irqrestore(&hp->lock, flags);

    tty_kref_put(tty);

    return IRQ_HANDLED;
}

/* for boot console, before the irq handler is running */
static int __init poll_for_state(struct hvsi_struct *hp, int state)
{
    unsigned long end_jiffies = jiffies + HVSI_TIMEOUT;

    for (;;) {
        hvsi_interrupt(hp->virq, (void *)hp); /* get pending data */

        if (hp->state == state)
            return 0;

        mdelay(5);
        if (time_after(jiffies, end_jiffies))
            return -EIO;
    }
}

/* wait for irq handler to change our state */
static int wait_for_state(struct hvsi_struct *hp, int state)
{
    int ret = 0;

    if (!wait_event_timeout(hp->stateq, (hp->state == state), HVSI_TIMEOUT))
        ret = -EIO;

    return ret;
}

static int hvsi_query(struct hvsi_struct *hp, uint16_t verb)
{
    struct hvsi_query packet __ALIGNED__;
    int wrote;

    packet.hdr.type = VS_QUERY_PACKET_HEADER;
    packet.hdr.len = sizeof(struct hvsi_query);
    packet.hdr.seqno = atomic_inc_return(&hp->seqno);
    packet.verb = verb;

    pr_debug("%s: sending %i bytes\n", __func__, packet.hdr.len);
    dbg_dump_hex((uint8_t*)&packet, packet.hdr.len);

    wrote = hvc_put_chars(hp->vtermno, (char *)&packet, packet.hdr.len);
    if (wrote != packet.hdr.len) {
        printk(KERN_ERR "hvsi%i: couldn't send query (%i)!\n", hp->index,
            wrote);
        return -EIO;
    }

    return 0;
}

static int hvsi_get_mctrl(struct hvsi_struct *hp)
{
    int ret;

    set_state(hp, HVSI_WAIT_FOR_MCTRL_RESPONSE);
    hvsi_query(hp, VSV_SEND_MODEM_CTL_STATUS);

    ret = hvsi_wait(hp, HVSI_OPEN);
    if (ret < 0) {
        printk(KERN_ERR "hvsi%i: didn't get modem flags\n", hp->index);
        set_state(hp, HVSI_OPEN);
        return ret;
    }

    pr_debug("%s: mctrl 0x%x\n", __func__, hp->mctrl);

    return 0;
}

/* note that we can only set DTR */
static int hvsi_set_mctrl(struct hvsi_struct *hp, uint16_t mctrl)
{
    struct hvsi_control packet __ALIGNED__;
    int wrote;

    packet.hdr.type = VS_CONTROL_PACKET_HEADER,
    packet.hdr.seqno = atomic_inc_return(&hp->seqno);
    packet.hdr.len = sizeof(struct hvsi_control);
    packet.verb = VSV_SET_MODEM_CTL;
    packet.mask = HVSI_TSDTR;

    if (mctrl & TIOCM_DTR)
        packet.word = HVSI_TSDTR;

    pr_debug("%s: sending %i bytes\n", __func__, packet.hdr.len);
    dbg_dump_hex((uint8_t*)&packet, packet.hdr.len);

    wrote = hvc_put_chars(hp->vtermno, (char *)&packet, packet.hdr.len);
    if (wrote != packet.hdr.len) {
        printk(KERN_ERR "hvsi%i: couldn't set DTR!\n", hp->index);
        return -EIO;
    }

    return 0;
}

static void hvsi_drain_input(struct hvsi_struct *hp)
{
    uint8_t buf[HVSI_MAX_READ] __ALIGNED__;
    unsigned long end_jiffies = jiffies + HVSI_TIMEOUT;

    while (time_before(end_jiffies, jiffies))
        if (0 == hvsi_read(hp, buf, HVSI_MAX_READ))
            break;
}

static int hvsi_handshake(struct hvsi_struct *hp)
{
    int ret;

    /*
     * We could have a CLOSE or other data waiting for us before we even try
     * to open; try to throw it all away so we don't get confused. (CLOSE
     * is the first message sent up the pipe when the FSP comes online. We
     * need to distinguish between "it came up a while ago and we're the first
     * user" and "it was just reset before it saw our handshake packet".)
     */
    hvsi_drain_input(hp);

    set_state(hp, HVSI_WAIT_FOR_VER_RESPONSE);
    ret = hvsi_query(hp, VSV_SEND_VERSION_NUMBER);
    if (ret < 0) {
        printk(KERN_ERR "hvsi%i: couldn't send version query\n", hp->index);
        return ret;
    }

    ret = hvsi_wait(hp, HVSI_OPEN);
    if (ret < 0)
        return ret;

    return 0;
}

static void hvsi_handshaker(struct work_struct *work)
{
    struct hvsi_struct *hp =
        container_of(work, struct hvsi_struct, handshaker);

    if (hvsi_handshake(hp) >= 0)
        return;

    printk(KERN_ERR "hvsi%i: re-handshaking failed\n", hp->index);
    if (is_console(hp)) {
        /*
         * ttys will re-attempt the handshake via hvsi_open, but
         * the console will not.
         */
        printk(KERN_ERR "hvsi%i: lost console!\n", hp->index);
    }
}

static int hvsi_put_chars(struct hvsi_struct *hp, const char *buf, int count)
{
    struct hvsi_data packet __ALIGNED__;
    int ret;

    BUG_ON(count > HVSI_MAX_OUTGOING_DATA);

    packet.hdr.type = VS_DATA_PACKET_HEADER;
    packet.hdr.seqno = atomic_inc_return(&hp->seqno);
    packet.hdr.len = count + sizeof(struct hvsi_header);
    memcpy(&packet.data, buf, count);

    ret = hvc_put_chars(hp->vtermno, (char *)&packet, packet.hdr.len);
    if (ret == packet.hdr.len) {
        /* return the number of chars written, not the packet length */
        return count;
    }
    return ret; /* return any errors */
}

static void hvsi_close_protocol(struct hvsi_struct *hp)
{
    struct hvsi_control packet __ALIGNED__;

    packet.hdr.type = VS_CONTROL_PACKET_HEADER;
    packet.hdr.seqno = atomic_inc_return(&hp->seqno);
    packet.hdr.len = 6;
    packet.verb = VSV_CLOSE_PROTOCOL;

    pr_debug("%s: sending %i bytes\n", __func__, packet.hdr.len);
    dbg_dump_hex((uint8_t*)&packet, packet.hdr.len);

    hvc_put_chars(hp->vtermno, (char *)&packet, packet.hdr.len);
}

static int hvsi_open(struct tty_struct *tty, struct file *filp)
{
    struct hvsi_struct *hp;
    unsigned long flags;
    int ret;

    pr_debug("%s\n", __func__);

    hp = &hvsi_ports[tty->index];

    tty->driver_data = hp;

    mb();
    if (hp->state == HVSI_FSP_DIED)
        return -EIO;

    tty_port_tty_set(&hp->port, tty);
    spin_lock_irqsave(&hp->lock, flags);
    hp->port.count++;
    atomic_set(&hp->seqno, 0);
    h_vio_signal(hp->vtermno, VIO_IRQ_ENABLE);
    spin_unlock_irqrestore(&hp->lock, flags);

    if (is_console(hp))
        return 0; /* this has already been handshaked as the console */

    ret = hvsi_handshake(hp);
    if (ret < 0) {
        printk(KERN_ERR "%s: HVSI handshaking failed\n", tty->name);
        return ret;
    }

    ret = hvsi_get_mctrl(hp);
    if (ret < 0) {
        printk(KERN_ERR "%s: couldn't get initial modem flags\n", tty->name);
        return ret;
    }

    ret = hvsi_set_mctrl(hp, hp->mctrl | TIOCM_DTR);
    if (ret < 0) {
        printk(KERN_ERR "%s: couldn't set DTR\n", tty->name);
        return ret;
    }

    return 0;
}

/* wait for hvsi_write_worker to empty hp->outbuf */
static void hvsi_flush_output(struct hvsi_struct *hp)
{
    wait_event_timeout(hp->emptyq, (hp->n_outbuf <= 0), HVSI_TIMEOUT);

    /* 'writer' could still be pending if it didn't see n_outbuf = 0 yet */
    cancel_delayed_work_sync(&hp->writer);
    flush_work(&hp->handshaker);

    /*
     * it's also possible that our timeout expired and hvsi_write_worker
     * didn't manage to push outbuf. poof.
     */
    hp->n_outbuf = 0;
}

static void hvsi_close(struct tty_struct *tty, struct file *filp)
{
    struct hvsi_struct *hp = tty->driver_data;
    unsigned long flags;

    pr_debug("%s\n", __func__);

    if (tty_hung_up_p(filp))
        return;

    spin_lock_irqsave(&hp->lock, flags);

    if (--hp->port.count == 0) {
        tty_port_tty_set(&hp->port, NULL);
        hp->inbuf_end = hp->inbuf; /* discard remaining partial packets */

        /* only close down connection if it is not the console */
        if (!is_console(hp)) {
            h_vio_signal(hp->vtermno, VIO_IRQ_DISABLE); /* no more irqs */
            __set_state(hp, HVSI_CLOSED);
            /*
             * any data delivered to the tty layer after this will be
             * discarded (except for XON/XOFF)
             */
            tty->closing = 1;

            spin_unlock_irqrestore(&hp->lock, flags);

            /* let any existing irq handlers finish. no more will start. */
            synchronize_irq(hp->virq);

            /* hvsi_write_worker will re-schedule until outbuf is empty. */
            hvsi_flush_output(hp);

            /* tell FSP to stop sending data */
            hvsi_close_protocol(hp);

            /*
             * drain anything FSP is still in the middle of sending, and let
             * hvsi_handshake drain the rest on the next open.
             */
            hvsi_drain_input(hp);

            spin_lock_irqsave(&hp->lock, flags);
        }
    } else if (hp->port.count < 0)
        printk(KERN_ERR "hvsi_close %lu: oops, count is %d\n",
               hp - hvsi_ports, hp->port.count);

    spin_unlock_irqrestore(&hp->lock, flags);
}

static void hvsi_hangup(struct tty_struct *tty)
{
    struct hvsi_struct *hp = tty->driver_data;
    unsigned long flags;

    pr_debug("%s\n", __func__);

    tty_port_tty_set(&hp->port, NULL);

    spin_lock_irqsave(&hp->lock, flags);
    hp->port.count = 0;
    hp->n_outbuf = 0;
    spin_unlock_irqrestore(&hp->lock, flags);
}

/* called with hp->lock held */
static void hvsi_push(struct hvsi_struct *hp)
{
    int n;

    if (hp->n_outbuf <= 0)
        return;

    n = hvsi_put_chars(hp, hp->outbuf, hp->n_outbuf);
    if (n > 0) {
        /* success */
        pr_debug("%s: wrote %i chars\n", __func__, n);
        hp->n_outbuf = 0;
    } else if (n == -EIO) {
        __set_state(hp, HVSI_FSP_DIED);
        printk(KERN_ERR "hvsi%i: service processor died\n", hp->index);
    }
}

/* hvsi_write_worker will keep rescheduling itself until outbuf is empty */
static void hvsi_write_worker(struct work_struct *work)
{
    struct hvsi_struct *hp =
        container_of(work, struct hvsi_struct, writer.work);
    struct tty_struct *tty;
    unsigned long flags;
#ifdef DEBUG
    static long start_j = 0;

    if (start_j == 0)
        start_j = jiffies;
#endif /* DEBUG */

    spin_lock_irqsave(&hp->lock, flags);

    pr_debug("%s: %i chars in buffer\n", __func__, hp->n_outbuf);

    if (!is_open(hp)) {
        /*
         * We could have a non-open connection if the service processor died
         * while we were busily scheduling ourselves. In that case, it could
         * be minutes before the service processor comes back, so only try
         * again once a second.
         */
        schedule_delayed_work(&hp->writer, HZ);
        goto out;
    }

    hvsi_push(hp);
    if (hp->n_outbuf > 0)
        schedule_delayed_work(&hp->writer, 10);
    else {
#ifdef DEBUG
        pr_debug("%s: outbuf emptied after %li jiffies\n", __func__,
                jiffies - start_j);
        start_j = 0;
#endif /* DEBUG */
        wake_up_all(&hp->emptyq);
        tty = tty_port_tty_get(&hp->port);
        if (tty) {
            tty_wakeup(tty);
            tty_kref_put(tty);
        }
    }

out:
    spin_unlock_irqrestore(&hp->lock, flags);
}

static int hvsi_write_room(struct tty_struct *tty)
{
    struct hvsi_struct *hp = tty->driver_data;

    return N_OUTBUF - hp->n_outbuf;
}

static int hvsi_chars_in_buffer(struct tty_struct *tty)
{
    struct hvsi_struct *hp = tty->driver_data;

    return hp->n_outbuf;
}

static int hvsi_write(struct tty_struct *tty,
             const unsigned char *buf, int count)
{
    struct hvsi_struct *hp = tty->driver_data;
    const char *source = buf;
    unsigned long flags;
    int total = 0;
    int origcount = count;

    spin_lock_irqsave(&hp->lock, flags);

    pr_debug("%s: %i chars in buffer\n", __func__, hp->n_outbuf);

    if (!is_open(hp)) {
        /* we're either closing or not yet open; don't accept data */
        pr_debug("%s: not open\n", __func__);
        goto out;
    }

    /*
     * when the hypervisor buffer (16K) fills, data will stay in hp->outbuf
     * and hvsi_write_worker will be scheduled. subsequent hvsi_write() calls
     * will see there is no room in outbuf and return.
     */
    while ((count > 0) && (hvsi_write_room(tty) > 0)) {
        int chunksize = min(count, hvsi_write_room(tty));

        BUG_ON(hp->n_outbuf < 0);
        memcpy(hp->outbuf + hp->n_outbuf, source, chunksize);
        hp->n_outbuf += chunksize;

        total += chunksize;
        source += chunksize;
        count -= chunksize;
        hvsi_push(hp);
    }

    if (hp->n_outbuf > 0) {
        /*
         * we weren't able to write it all to the hypervisor.
         * schedule another push attempt.
         */
        schedule_delayed_work(&hp->writer, 10);
    }

out:
    spin_unlock_irqrestore(&hp->lock, flags);

    if (total != origcount)
        pr_debug("%s: wanted %i, only wrote %i\n", __func__, origcount,
            total);

    return total;
}

/*
 * I have never seen throttle or unthrottle called, so this little throttle
 * buffering scheme may or may not work.
 */
static void hvsi_throttle(struct tty_struct *tty)
{
    struct hvsi_struct *hp = tty->driver_data;

    pr_debug("%s\n", __func__);

    h_vio_signal(hp->vtermno, VIO_IRQ_DISABLE);
}

static void hvsi_unthrottle(struct tty_struct *tty)
{
    struct hvsi_struct *hp = tty->driver_data;
    unsigned long flags;

    pr_debug("%s\n", __func__);

    spin_lock_irqsave(&hp->lock, flags);
    if (hp->n_throttle) {
        hvsi_send_overflow(hp, tty);
        tty_flip_buffer_push(tty);
    }
    spin_unlock_irqrestore(&hp->lock, flags);


    h_vio_signal(hp->vtermno, VIO_IRQ_ENABLE);
}

static int hvsi_tiocmget(struct tty_struct *tty)
{
    struct hvsi_struct *hp = tty->driver_data;

    hvsi_get_mctrl(hp);
    return hp->mctrl;
}

static int hvsi_tiocmset(struct tty_struct *tty,
                unsigned int set, unsigned int clear)
{
    struct hvsi_struct *hp = tty->driver_data;
    unsigned long flags;
    uint16_t new_mctrl;

    /* we can only alter DTR */
    clear &= TIOCM_DTR;
    set &= TIOCM_DTR;

    spin_lock_irqsave(&hp->lock, flags);

    new_mctrl = (hp->mctrl & ~clear) | set;

    if (hp->mctrl != new_mctrl) {
        hvsi_set_mctrl(hp, new_mctrl);
        hp->mctrl = new_mctrl;
    }
    spin_unlock_irqrestore(&hp->lock, flags);

    return 0;
}


static const struct tty_operations hvsi_ops = {
    .open = hvsi_open,
    .close = hvsi_close,
    .write = hvsi_write,
    .hangup = hvsi_hangup,
    .write_room = hvsi_write_room,
    .chars_in_buffer = hvsi_chars_in_buffer,
    .throttle = hvsi_throttle,
    .unthrottle = hvsi_unthrottle,
    .tiocmget = hvsi_tiocmget,
    .tiocmset = hvsi_tiocmset,
};

static int __init hvsi_init(void)
{
    int i;

    hvsi_driver = alloc_tty_driver(hvsi_count);
    if (!hvsi_driver)
        return -ENOMEM;

    hvsi_driver->driver_name = "hvsi";
    hvsi_driver->name = "hvsi";
    hvsi_driver->major = HVSI_MAJOR;
    hvsi_driver->minor_start = HVSI_MINOR;
    hvsi_driver->type = TTY_DRIVER_TYPE_SYSTEM;
    hvsi_driver->init_termios = tty_std_termios;
    hvsi_driver->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL;
    hvsi_driver->init_termios.c_ispeed = 9600;
    hvsi_driver->init_termios.c_ospeed = 9600;
    hvsi_driver->flags = TTY_DRIVER_REAL_RAW;
    tty_set_operations(hvsi_driver, &hvsi_ops);

    for (i=0; i < hvsi_count; i++) {
        struct hvsi_struct *hp = &hvsi_ports[i];
        int ret = 1;

        tty_port_link_device(&hp->port, hvsi_driver, i);

        ret = request_irq(hp->virq, hvsi_interrupt, 0, "hvsi", hp);
        if (ret)
            printk(KERN_ERR "HVSI: couldn't reserve irq 0x%x (error %i)\n",
                hp->virq, ret);
    }
    hvsi_wait = wait_for_state; /* irqs active now */

    if (tty_register_driver(hvsi_driver))
        panic("Couldn't register hvsi console driver\n");

    printk(KERN_DEBUG "HVSI: registered %i devices\n", hvsi_count);

    return 0;
}
device_initcall(hvsi_init);

/***** console (not tty) code: *****/

static void hvsi_console_print(struct console *console, const char *buf,
        unsigned int count)
{
    struct hvsi_struct *hp = &hvsi_ports[console->index];
    char c[HVSI_MAX_OUTGOING_DATA] __ALIGNED__;
    unsigned int i = 0, n = 0;
    int ret, donecr = 0;

    mb();
    if (!is_open(hp))
        return;

    /*
     * ugh, we have to translate LF -> CRLF ourselves, in place.
     * copied from hvc_console.c:
     */
    while (count > 0 || i > 0) {
        if (count > 0 && i < sizeof(c)) {
            if (buf[n] == '\n' && !donecr) {
                c[i++] = '\r';
                donecr = 1;
            } else {
                c[i++] = buf[n++];
                donecr = 0;
                --count;
            }
        } else {
            ret = hvsi_put_chars(hp, c, i);
            if (ret < 0)
                i = 0;
            i -= ret;
        }
    }
}

static struct tty_driver *hvsi_console_device(struct console *console,
    int *index)
{
    *index = console->index;
    return hvsi_driver;
}

static int __init hvsi_console_setup(struct console *console, char *options)
{
    struct hvsi_struct *hp;
    int ret;

    if (console->index < 0 || console->index >= hvsi_count)
        return -1;
    hp = &hvsi_ports[console->index];

    /* give the FSP a chance to change the baud rate when we re-open */
    hvsi_close_protocol(hp);

    ret = hvsi_handshake(hp);
    if (ret < 0)
        return ret;

    ret = hvsi_get_mctrl(hp);
    if (ret < 0)
        return ret;

    ret = hvsi_set_mctrl(hp, hp->mctrl | TIOCM_DTR);
    if (ret < 0)
        return ret;

    hp->flags |= HVSI_CONSOLE;

    return 0;
}

static struct console hvsi_console = {
    .name       = "hvsi",
    .write      = hvsi_console_print,
    .device     = hvsi_console_device,
    .setup      = hvsi_console_setup,
    .flags      = CON_PRINTBUFFER,
    .index      = -1,
};

static int __init hvsi_console_init(void)
{
    struct device_node *vty;

    hvsi_wait = poll_for_state; /* no irqs yet; must poll */

    /* search device tree for vty nodes */
    for (vty = of_find_compatible_node(NULL, "serial", "hvterm-protocol");
            vty != NULL;
            vty = of_find_compatible_node(vty, "serial", "hvterm-protocol")) {
        struct hvsi_struct *hp;
        const uint32_t *vtermno, *irq;

        vtermno = of_get_property(vty, "reg", NULL);
        irq = of_get_property(vty, "interrupts", NULL);
        if (!vtermno || !irq)
            continue;

        if (hvsi_count >= MAX_NR_HVSI_CONSOLES) {
            of_node_put(vty);
            break;
        }

        hp = &hvsi_ports[hvsi_count];
        INIT_DELAYED_WORK(&hp->writer, hvsi_write_worker);
        INIT_WORK(&hp->handshaker, hvsi_handshaker);
        init_waitqueue_head(&hp->emptyq);
        init_waitqueue_head(&hp->stateq);
        spin_lock_init(&hp->lock);
        tty_port_init(&hp->port);
        hp->index = hvsi_count;
        hp->inbuf_end = hp->inbuf;
        hp->state = HVSI_CLOSED;
        hp->vtermno = *vtermno;
        hp->virq = irq_create_mapping(NULL, irq[0]);
        if (hp->virq == 0) {
            printk(KERN_ERR "%s: couldn't create irq mapping for 0x%x\n",
                __func__, irq[0]);
            continue;
        }

        hvsi_count++;
    }

    if (hvsi_count)
        register_console(&hvsi_console);
    return 0;
}
console_initcall(hvsi_console_init);