// SPDX-License-Identifier: GPL-2.0
/*
 * Simulated Serial Driver (fake serial)
 *
 * This driver is mostly used for bringup purposes and will go away.
 * It has a strong dependency on the system console. All outputs
 * are rerouted to the same facility as the one used by printk which, in our
 * case means sys_sim.c console (goes via the simulator).
 *
 * Copyright (C) 1999-2000, 2002-2003 Hewlett-Packard Co
 *      Stephane Eranian <eranian@hpl.hp.com>
 *      David Mosberger-Tang <davidm@hpl.hp.com>
 */

#include <linux/init.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/major.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/capability.h>
#include <linux/circ_buf.h>
#include <linux/console.h>
#include <linux/irq.h>
#include <linux/module.h>
#include <linux/serial.h>
#include <linux/sysrq.h>
#include <linux/uaccess.h>

#include <asm/hpsim.h>

#include "hpsim_ssc.h"

#undef SIMSERIAL_DEBUG  /* define this to get some debug information */

#define KEYBOARD_INTR   3       /* must match with simulator! */

#define NR_PORTS        1       /* only one port for now */

struct serial_state {
        struct tty_port port;
        struct circ_buf xmit;
        int irq;
        int x_char;
};

static struct serial_state rs_table[NR_PORTS];

struct tty_driver *hp_simserial_driver;

static struct console *console;

static void receive_chars(struct tty_port *port)
{
        unsigned char ch;
        static unsigned char seen_esc = 0;

        while ( (ch = ia64_ssc(0, 0, 0, 0, SSC_GETCHAR)) ) {
                if (ch == 27 && seen_esc == 0) {
                        seen_esc = 1;
                        continue;
                } else if (seen_esc == 1 && ch == 'O') {
                        seen_esc = 2;
                        continue;
                } else if (seen_esc == 2) {
                        if (ch == 'P') /* F1 */
                                show_state();
#ifdef CONFIG_MAGIC_SYSRQ
                        if (ch == 'S') { /* F4 */
                                do {
                                        ch = ia64_ssc(0, 0, 0, 0, SSC_GETCHAR);
                                } while (!ch);
                                handle_sysrq(ch);
                        }
#endif
                        seen_esc = 0;
                        continue;
                }
                seen_esc = 0;

                if (tty_insert_flip_char(port, ch, TTY_NORMAL) == 0)
                        break;
        }
        tty_flip_buffer_push(port);
}

/*
 * This is the serial driver's interrupt routine for a single port
 */
static irqreturn_t rs_interrupt_single(int irq, void *dev_id)
{
        struct serial_state *info = dev_id;

        receive_chars(&info->port);

        return IRQ_HANDLED;
}

/*
 * -------------------------------------------------------------------
 * Here ends the serial interrupt routines.
 * -------------------------------------------------------------------
 */

static int rs_put_char(struct tty_struct *tty, unsigned char ch)
{
        struct serial_state *info = tty->driver_data;
        unsigned long flags;

        if (!info->xmit.buf)
                return 0;

        local_irq_save(flags);
        if (CIRC_SPACE(info->xmit.head, info->xmit.tail, SERIAL_XMIT_SIZE) == 0) {
                local_irq_restore(flags);
                return 0;
        }
        info->xmit.buf[info->xmit.head] = ch;
        info->xmit.head = (info->xmit.head + 1) & (SERIAL_XMIT_SIZE-1);
        local_irq_restore(flags);
        return 1;
}

static void transmit_chars(struct tty_struct *tty, struct serial_state *info,
                int *intr_done)
{
        int count;
        unsigned long flags;

        local_irq_save(flags);

        if (info->x_char) {
                char c = info->x_char;

                console->write(console, &c, 1);

                info->x_char = 0;

                goto out;
        }

        if (info->xmit.head == info->xmit.tail || tty->stopped) {
#ifdef SIMSERIAL_DEBUG
                printk("transmit_chars: head=%d, tail=%d, stopped=%d\n",
                       info->xmit.head, info->xmit.tail, tty->stopped);
#endif
                goto out;
        }
        /*
         * We removed the loop and try to do it in to chunks. We need
         * 2 operations maximum because it's a ring buffer.
         *
         * First from current to tail if possible.
         * Then from the beginning of the buffer until necessary
         */

        count = min(CIRC_CNT(info->xmit.head, info->xmit.tail, SERIAL_XMIT_SIZE),
                    SERIAL_XMIT_SIZE - info->xmit.tail);
        console->write(console, info->xmit.buf+info->xmit.tail, count);

        info->xmit.tail = (info->xmit.tail+count) & (SERIAL_XMIT_SIZE-1);

        /*
         * We have more at the beginning of the buffer
         */
        count = CIRC_CNT(info->xmit.head, info->xmit.tail, SERIAL_XMIT_SIZE);
        if (count) {
                console->write(console, info->xmit.buf, count);
                info->xmit.tail += count;
        }
out:
        local_irq_restore(flags);
}

static void rs_flush_chars(struct tty_struct *tty)
{
        struct serial_state *info = tty->driver_data;

        if (info->xmit.head == info->xmit.tail || tty->stopped ||
                        !info->xmit.buf)
                return;

        transmit_chars(tty, info, NULL);
}

static int rs_write(struct tty_struct * tty,
                    const unsigned char *buf, int count)
{
        struct serial_state *info = tty->driver_data;
        int     c, ret = 0;
        unsigned long flags;

        if (!info->xmit.buf)
                return 0;

        local_irq_save(flags);
        while (1) {
                c = CIRC_SPACE_TO_END(info->xmit.head, info->xmit.tail, SERIAL_XMIT_SIZE);
                if (count < c)
                        c = count;
                if (c <= 0) {
                        break;
                }
                memcpy(info->xmit.buf + info->xmit.head, buf, c);
                info->xmit.head = ((info->xmit.head + c) &
                                   (SERIAL_XMIT_SIZE-1));
                buf += c;
                count -= c;
                ret += c;
        }
        local_irq_restore(flags);
        /*
         * Hey, we transmit directly from here in our case
         */
        if (CIRC_CNT(info->xmit.head, info->xmit.tail, SERIAL_XMIT_SIZE) &&
                        !tty->stopped)
                transmit_chars(tty, info, NULL);

        return ret;
}

static int rs_write_room(struct tty_struct *tty)
{
        struct serial_state *info = tty->driver_data;

        return CIRC_SPACE(info->xmit.head, info->xmit.tail, SERIAL_XMIT_SIZE);
}

static int rs_chars_in_buffer(struct tty_struct *tty)
{
        struct serial_state *info = tty->driver_data;

        return CIRC_CNT(info->xmit.head, info->xmit.tail, SERIAL_XMIT_SIZE);
}

static void rs_flush_buffer(struct tty_struct *tty)
{
        struct serial_state *info = tty->driver_data;
        unsigned long flags;

        local_irq_save(flags);
        info->xmit.head = info->xmit.tail = 0;
        local_irq_restore(flags);

        tty_wakeup(tty);
}

/*
 * This function is used to send a high-priority XON/XOFF character to
 * the device
 */
static void rs_send_xchar(struct tty_struct *tty, char ch)
{
        struct serial_state *info = tty->driver_data;

        info->x_char = ch;
        if (ch) {
                /*
                 * I guess we could call console->write() directly but
                 * let's do that for now.
                 */
                transmit_chars(tty, info, NULL);
        }
}

/*
 * ------------------------------------------------------------
 * rs_throttle()
 *
 * This routine is called by the upper-layer tty layer to signal that
 * incoming characters should be throttled.
 * ------------------------------------------------------------
 */
static void rs_throttle(struct tty_struct * tty)
{
        if (I_IXOFF(tty))
                rs_send_xchar(tty, STOP_CHAR(tty));

        printk(KERN_INFO "simrs_throttle called\n");
}

static void rs_unthrottle(struct tty_struct * tty)
{
        struct serial_state *info = tty->driver_data;

        if (I_IXOFF(tty)) {
                if (info->x_char)
                        info->x_char = 0;
                else
                        rs_send_xchar(tty, START_CHAR(tty));
        }
        printk(KERN_INFO "simrs_unthrottle called\n");
}

static int rs_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
{
        if ((cmd != TIOCGSERIAL) && (cmd != TIOCSSERIAL) &&
            (cmd != TIOCSERCONFIG) && (cmd != TIOCSERGSTRUCT) &&
            (cmd != TIOCMIWAIT)) {
                if (tty_io_error(tty))
                    return -EIO;
        }

        switch (cmd) {
        case TIOCGSERIAL:
        case TIOCSSERIAL:
        case TIOCSERGSTRUCT:
        case TIOCMIWAIT:
                return 0;
        case TIOCSERCONFIG:
        case TIOCSERGETLSR: /* Get line status register */
                return -EINVAL;
        case TIOCSERGWILD:
        case TIOCSERSWILD:
                /* "setserial -W" is called in Debian boot */
                printk (KERN_INFO "TIOCSER?WILD ioctl obsolete, ignored.\n");
                return 0;
        }
        return -ENOIOCTLCMD;
}

#define RELEVANT_IFLAG(iflag) (iflag & (IGNBRK|BRKINT|IGNPAR|PARMRK|INPCK))

/*
 * This routine will shutdown a serial port; interrupts are disabled, and
 * DTR is dropped if the hangup on close termio flag is on.
 */
static void shutdown(struct tty_port *port)
{
        struct serial_state *info = container_of(port, struct serial_state,
                        port);
        unsigned long flags;

        local_irq_save(flags);
        if (info->irq)
                free_irq(info->irq, info);

        if (info->xmit.buf) {
                free_page((unsigned long) info->xmit.buf);
                info->xmit.buf = NULL;
        }
        local_irq_restore(flags);
}

static void rs_close(struct tty_struct *tty, struct file * filp)
{
        struct serial_state *info = tty->driver_data;

        tty_port_close(&info->port, tty, filp);
}

static void rs_hangup(struct tty_struct *tty)
{
        struct serial_state *info = tty->driver_data;

        rs_flush_buffer(tty);
        tty_port_hangup(&info->port);
}

static int activate(struct tty_port *port, struct tty_struct *tty)
{
        struct serial_state *state = container_of(port, struct serial_state,
                        port);
        unsigned long flags, page;
        int retval = 0;

        page = get_zeroed_page(GFP_KERNEL);
        if (!page)
                return -ENOMEM;

        local_irq_save(flags);

        if (state->xmit.buf)
                free_page(page);
        else
                state->xmit.buf = (unsigned char *) page;

        if (state->irq) {
                retval = request_irq(state->irq, rs_interrupt_single, 0,
                                "simserial", state);
                if (retval)
                        goto errout;
        }

        state->xmit.head = state->xmit.tail = 0;
errout:
        local_irq_restore(flags);
        return retval;
}


/*
 * This routine is called whenever a serial port is opened.  It
 * enables interrupts for a serial port, linking in its async structure into
 * the IRQ chain.   It also performs the serial-specific
 * initialization for the tty structure.
 */
static int rs_open(struct tty_struct *tty, struct file * filp)
{
        struct serial_state *info = rs_table + tty->index;
        struct tty_port *port = &info->port;

        tty->driver_data = info;
        port->low_latency = (port->flags & ASYNC_LOW_LATENCY) ? 1 : 0;

        /*
         * figure out which console to use (should be one already)
         */
        console = console_drivers;
        while (console) {
                if ((console->flags & CON_ENABLED) && console->write) break;
                console = console->next;
        }

        return tty_port_open(port, tty, filp);
}

/*
 * /proc fs routines....
 */

static int rs_proc_show(struct seq_file *m, void *v)
{
        int i;

        seq_printf(m, "simserinfo:1.0\n");
        for (i = 0; i < NR_PORTS; i++)
                seq_printf(m, "%d: uart:16550 port:3F8 irq:%d\n",
                       i, rs_table[i].irq);
        return 0;
}

static const struct tty_operations hp_ops = {
        .open = rs_open,
        .close = rs_close,
        .write = rs_write,
        .put_char = rs_put_char,
        .flush_chars = rs_flush_chars,
        .write_room = rs_write_room,
        .chars_in_buffer = rs_chars_in_buffer,
        .flush_buffer = rs_flush_buffer,
        .ioctl = rs_ioctl,
        .throttle = rs_throttle,
        .unthrottle = rs_unthrottle,
        .send_xchar = rs_send_xchar,
        .hangup = rs_hangup,
        .proc_show = rs_proc_show,
};

static const struct tty_port_operations hp_port_ops = {
        .activate = activate,
        .shutdown = shutdown,
};

static int __init simrs_init(void)
{
        struct serial_state *state;
        int retval;

        if (!ia64_platform_is("hpsim"))
                return -ENODEV;

        hp_simserial_driver = alloc_tty_driver(NR_PORTS);
        if (!hp_simserial_driver)
                return -ENOMEM;

        printk(KERN_INFO "SimSerial driver with no serial options enabled\n");

        /* Initialize the tty_driver structure */

        hp_simserial_driver->driver_name = "simserial";
        hp_simserial_driver->name = "ttyS";
        hp_simserial_driver->major = TTY_MAJOR;
        hp_simserial_driver->minor_start = 64;
        hp_simserial_driver->type = TTY_DRIVER_TYPE_SERIAL;
        hp_simserial_driver->subtype = SERIAL_TYPE_NORMAL;
        hp_simserial_driver->init_termios = tty_std_termios;
        hp_simserial_driver->init_termios.c_cflag =
                B9600 | CS8 | CREAD | HUPCL | CLOCAL;
        hp_simserial_driver->flags = TTY_DRIVER_REAL_RAW;
        tty_set_operations(hp_simserial_driver, &hp_ops);

        state = rs_table;
        tty_port_init(&state->port);
        state->port.ops = &hp_port_ops;
        state->port.close_delay = 0; /* XXX really 0? */

        retval = hpsim_get_irq(KEYBOARD_INTR);
        if (retval < 0) {
                printk(KERN_ERR "%s: out of interrupt vectors!\n",
                                __func__);
                goto err_free_tty;
        }

        state->irq = retval;

        /* the port is imaginary */
        printk(KERN_INFO "ttyS0 at 0x03f8 (irq = %d) is a 16550\n", state->irq);

        tty_port_link_device(&state->port, hp_simserial_driver, 0);
        retval = tty_register_driver(hp_simserial_driver);
        if (retval) {
                printk(KERN_ERR "Couldn't register simserial driver\n");
                goto err_free_tty;
        }

        return 0;
err_free_tty:
        put_tty_driver(hp_simserial_driver);
        tty_port_destroy(&state->port);
        return retval;
}

#ifndef MODULE
__initcall(simrs_init);
#endif