mm owner: fix race between swapoff and exit

[linux-2.6/next.git] / drivers / serial / sunhv.c

/* sunhv.c: Serial driver for SUN4V hypervisor console.
 *
 * Copyright (C) 2006, 2007 David S. Miller (davem@davemloft.net)
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/major.h>
#include <linux/circ_buf.h>
#include <linux/serial.h>
#include <linux/sysrq.h>
#include <linux/console.h>
#include <linux/spinlock.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/of_device.h>

#include <asm/hypervisor.h>
#include <asm/spitfire.h>
#include <asm/prom.h>
#include <asm/irq.h>

#if defined(CONFIG_MAGIC_SYSRQ)
#define SUPPORT_SYSRQ
#endif

#include <linux/serial_core.h>

#include "suncore.h"

#define CON_BREAK       ((long)-1)
#define CON_HUP         ((long)-2)

#define IGNORE_BREAK    0x1
#define IGNORE_ALL      0x2

static char *con_write_page;
static char *con_read_page;

static int hung_up = 0;

static void transmit_chars_putchar(struct uart_port *port, struct circ_buf *xmit)
{
        while (!uart_circ_empty(xmit)) {
                long status = sun4v_con_putchar(xmit->buf[xmit->tail]);

                if (status != HV_EOK)
                        break;

                xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
                port->icount.tx++;
        }
}

static void transmit_chars_write(struct uart_port *port, struct circ_buf *xmit)
{
        while (!uart_circ_empty(xmit)) {
                unsigned long ra = __pa(xmit->buf + xmit->tail);
                unsigned long len, status, sent;

                len = CIRC_CNT_TO_END(xmit->head, xmit->tail,
                                      UART_XMIT_SIZE);
                status = sun4v_con_write(ra, len, &sent);
                if (status != HV_EOK)
                        break;
                xmit->tail = (xmit->tail + sent) & (UART_XMIT_SIZE - 1);
                port->icount.tx += sent;
        }
}

static int receive_chars_getchar(struct uart_port *port, struct tty_struct *tty)
{
        int saw_console_brk = 0;
        int limit = 10000;

        while (limit-- > 0) {
                long status;
                long c = sun4v_con_getchar(&status);

                if (status == HV_EWOULDBLOCK)
                        break;

                if (c == CON_BREAK) {
                        if (uart_handle_break(port))
                                continue;
                        saw_console_brk = 1;
                        c = 0;
                }

                if (c == CON_HUP) {
                        hung_up = 1;
                        uart_handle_dcd_change(port, 0);
                } else if (hung_up) {
                        hung_up = 0;
                        uart_handle_dcd_change(port, 1);
                }

                if (tty == NULL) {
                        uart_handle_sysrq_char(port, c);
                        continue;
                }

                port->icount.rx++;

                if (uart_handle_sysrq_char(port, c))
                        continue;

                tty_insert_flip_char(tty, c, TTY_NORMAL);
        }

        return saw_console_brk;
}

static int receive_chars_read(struct uart_port *port, struct tty_struct *tty)
{
        int saw_console_brk = 0;
        int limit = 10000;

        while (limit-- > 0) {
                unsigned long ra = __pa(con_read_page);
                unsigned long bytes_read, i;
                long stat = sun4v_con_read(ra, PAGE_SIZE, &bytes_read);

                if (stat != HV_EOK) {
                        bytes_read = 0;

                        if (stat == CON_BREAK) {
                                if (uart_handle_break(port))
                                        continue;
                                saw_console_brk = 1;
                                *con_read_page = 0;
                                bytes_read = 1;
                        } else if (stat == CON_HUP) {
                                hung_up = 1;
                                uart_handle_dcd_change(port, 0);
                                continue;
                        } else {
                                /* HV_EWOULDBLOCK, etc.  */
                                break;
                        }
                }

                if (hung_up) {
                        hung_up = 0;
                        uart_handle_dcd_change(port, 1);
                }

                for (i = 0; i < bytes_read; i++)
                        uart_handle_sysrq_char(port, con_read_page[i]);

                if (tty == NULL)
                        continue;

                port->icount.rx += bytes_read;

                tty_insert_flip_string(tty, con_read_page, bytes_read);
        }

        return saw_console_brk;
}

struct sunhv_ops {
        void (*transmit_chars)(struct uart_port *port, struct circ_buf *xmit);
        int (*receive_chars)(struct uart_port *port, struct tty_struct *tty);
};

static struct sunhv_ops bychar_ops = {
        .transmit_chars = transmit_chars_putchar,
        .receive_chars = receive_chars_getchar,
};

static struct sunhv_ops bywrite_ops = {
        .transmit_chars = transmit_chars_write,
        .receive_chars = receive_chars_read,
};

static struct sunhv_ops *sunhv_ops = &bychar_ops;

static struct tty_struct *receive_chars(struct uart_port *port)
{
        struct tty_struct *tty = NULL;

        if (port->info != NULL)         /* Unopened serial console */
                tty = port->info->port.tty;

        if (sunhv_ops->receive_chars(port, tty))
                sun_do_break();

        return tty;
}

static void transmit_chars(struct uart_port *port)
{
        struct circ_buf *xmit;

        if (!port->info)
                return;

        xmit = &port->info->xmit;
        if (uart_circ_empty(xmit) || uart_tx_stopped(port))
                return;

        sunhv_ops->transmit_chars(port, xmit);

        if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
                uart_write_wakeup(port);
}

static irqreturn_t sunhv_interrupt(int irq, void *dev_id)
{
        struct uart_port *port = dev_id;
        struct tty_struct *tty;
        unsigned long flags;

        spin_lock_irqsave(&port->lock, flags);
        tty = receive_chars(port);
        transmit_chars(port);
        spin_unlock_irqrestore(&port->lock, flags);

        if (tty)
                tty_flip_buffer_push(tty);

        return IRQ_HANDLED;
}

/* port->lock is not held.  */
static unsigned int sunhv_tx_empty(struct uart_port *port)
{
        /* Transmitter is always empty for us.  If the circ buffer
         * is non-empty or there is an x_char pending, our caller
         * will do the right thing and ignore what we return here.
         */
        return TIOCSER_TEMT;
}

/* port->lock held by caller.  */
static void sunhv_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
        return;
}

/* port->lock is held by caller and interrupts are disabled.  */
static unsigned int sunhv_get_mctrl(struct uart_port *port)
{
        return TIOCM_DSR | TIOCM_CAR | TIOCM_CTS;
}

/* port->lock held by caller.  */
static void sunhv_stop_tx(struct uart_port *port)
{
        return;
}

/* port->lock held by caller.  */
static void sunhv_start_tx(struct uart_port *port)
{
        transmit_chars(port);
}

/* port->lock is not held.  */
static void sunhv_send_xchar(struct uart_port *port, char ch)
{
        unsigned long flags;
        int limit = 10000;

        spin_lock_irqsave(&port->lock, flags);

        while (limit-- > 0) {
                long status = sun4v_con_putchar(ch);
                if (status == HV_EOK)
                        break;
                udelay(1);
        }

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

/* port->lock held by caller.  */
static void sunhv_stop_rx(struct uart_port *port)
{
}

/* port->lock held by caller.  */
static void sunhv_enable_ms(struct uart_port *port)
{
}

/* port->lock is not held.  */
static void sunhv_break_ctl(struct uart_port *port, int break_state)
{
        if (break_state) {
                unsigned long flags;
                int limit = 10000;

                spin_lock_irqsave(&port->lock, flags);

                while (limit-- > 0) {
                        long status = sun4v_con_putchar(CON_BREAK);
                        if (status == HV_EOK)
                                break;
                        udelay(1);
                }

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

/* port->lock is not held.  */
static int sunhv_startup(struct uart_port *port)
{
        return 0;
}

/* port->lock is not held.  */
static void sunhv_shutdown(struct uart_port *port)
{
}

/* port->lock is not held.  */
static void sunhv_set_termios(struct uart_port *port, struct ktermios *termios,
                              struct ktermios *old)
{
        unsigned int baud = uart_get_baud_rate(port, termios, old, 0, 4000000);
        unsigned int quot = uart_get_divisor(port, baud);
        unsigned int iflag, cflag;
        unsigned long flags;

        spin_lock_irqsave(&port->lock, flags);

        iflag = termios->c_iflag;
        cflag = termios->c_cflag;

        port->ignore_status_mask = 0;
        if (iflag & IGNBRK)
                port->ignore_status_mask |= IGNORE_BREAK;
        if ((cflag & CREAD) == 0)
                port->ignore_status_mask |= IGNORE_ALL;

        /* XXX */
        uart_update_timeout(port, cflag,
                            (port->uartclk / (16 * quot)));

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

static const char *sunhv_type(struct uart_port *port)
{
        return "SUN4V HCONS";
}

static void sunhv_release_port(struct uart_port *port)
{
}

static int sunhv_request_port(struct uart_port *port)
{
        return 0;
}

static void sunhv_config_port(struct uart_port *port, int flags)
{
}

static int sunhv_verify_port(struct uart_port *port, struct serial_struct *ser)
{
        return -EINVAL;
}

static struct uart_ops sunhv_pops = {
        .tx_empty       = sunhv_tx_empty,
        .set_mctrl      = sunhv_set_mctrl,
        .get_mctrl      = sunhv_get_mctrl,
        .stop_tx        = sunhv_stop_tx,
        .start_tx       = sunhv_start_tx,
        .send_xchar     = sunhv_send_xchar,
        .stop_rx        = sunhv_stop_rx,
        .enable_ms      = sunhv_enable_ms,
        .break_ctl      = sunhv_break_ctl,
        .startup        = sunhv_startup,
        .shutdown       = sunhv_shutdown,
        .set_termios    = sunhv_set_termios,
        .type           = sunhv_type,
        .release_port   = sunhv_release_port,
        .request_port   = sunhv_request_port,
        .config_port    = sunhv_config_port,
        .verify_port    = sunhv_verify_port,
};

static struct uart_driver sunhv_reg = {
        .owner                  = THIS_MODULE,
        .driver_name            = "sunhv",
        .dev_name               = "ttyS",
        .major                  = TTY_MAJOR,
};

static struct uart_port *sunhv_port;

/* Copy 's' into the con_write_page, decoding "\n" into
 * "\r\n" along the way.  We have to return two lengths
 * because the caller needs to know how much to advance
 * 's' and also how many bytes to output via con_write_page.
 */
static int fill_con_write_page(const char *s, unsigned int n,
                               unsigned long *page_bytes)
{
        const char *orig_s = s;
        char *p = con_write_page;
        int left = PAGE_SIZE;

        while (n--) {
                if (*s == '\n') {
                        if (left < 2)
                                break;
                        *p++ = '\r';
                        left--;
                } else if (left < 1)
                        break;
                *p++ = *s++;
                left--;
        }
        *page_bytes = p - con_write_page;
        return s - orig_s;
}

static void sunhv_console_write_paged(struct console *con, const char *s, unsigned n)
{
        struct uart_port *port = sunhv_port;
        unsigned long flags;
        int locked = 1;

        local_irq_save(flags);
        if (port->sysrq) {
                locked = 0;
        } else if (oops_in_progress) {
                locked = spin_trylock(&port->lock);
        } else
                spin_lock(&port->lock);

        while (n > 0) {
                unsigned long ra = __pa(con_write_page);
                unsigned long page_bytes;
                unsigned int cpy = fill_con_write_page(s, n,
                                                       &page_bytes);

                n -= cpy;
                s += cpy;
                while (page_bytes > 0) {
                        unsigned long written;
                        int limit = 1000000;

                        while (limit--) {
                                unsigned long stat;

                                stat = sun4v_con_write(ra, page_bytes,
                                                       &written);
                                if (stat == HV_EOK)
                                        break;
                                udelay(1);
                        }
                        if (limit <= 0)
                                break;
                        page_bytes -= written;
                        ra += written;
                }
        }

        if (locked)
                spin_unlock(&port->lock);
        local_irq_restore(flags);
}

static inline void sunhv_console_putchar(struct uart_port *port, char c)
{
        int limit = 1000000;

        while (limit-- > 0) {
                long status = sun4v_con_putchar(c);
                if (status == HV_EOK)
                        break;
                udelay(1);
        }
}

static void sunhv_console_write_bychar(struct console *con, const char *s, unsigned n)
{
        struct uart_port *port = sunhv_port;
        unsigned long flags;
        int i, locked = 1;

        local_irq_save(flags);
        if (port->sysrq) {
                locked = 0;
        } else if (oops_in_progress) {
                locked = spin_trylock(&port->lock);
        } else
                spin_lock(&port->lock);

        for (i = 0; i < n; i++) {
                if (*s == '\n')
                        sunhv_console_putchar(port, '\r');
                sunhv_console_putchar(port, *s++);
        }

        if (locked)
                spin_unlock(&port->lock);
        local_irq_restore(flags);
}

static struct console sunhv_console = {
        .name   =       "ttyHV",
        .write  =       sunhv_console_write_bychar,
        .device =       uart_console_device,
        .flags  =       CON_PRINTBUFFER,
        .index  =       -1,
        .data   =       &sunhv_reg,
};

static int __devinit hv_probe(struct of_device *op, const struct of_device_id *match)
{
        struct uart_port *port;
        unsigned long minor;
        int err;

        if (op->irqs[0] == 0xffffffff)
                return -ENODEV;

        port = kzalloc(sizeof(struct uart_port), GFP_KERNEL);
        if (unlikely(!port))
                return -ENOMEM;

        minor = 1;
        if (sun4v_hvapi_register(HV_GRP_CORE, 1, &minor) == 0 &&
            minor >= 1) {
                err = -ENOMEM;
                con_write_page = kzalloc(PAGE_SIZE, GFP_KERNEL);
                if (!con_write_page)
                        goto out_free_port;

                con_read_page = kzalloc(PAGE_SIZE, GFP_KERNEL);
                if (!con_read_page)
                        goto out_free_con_write_page;

                sunhv_console.write = sunhv_console_write_paged;
                sunhv_ops = &bywrite_ops;
        }

        sunhv_port = port;

        port->line = 0;
        port->ops = &sunhv_pops;
        port->type = PORT_SUNHV;
        port->uartclk = ( 29491200 / 16 ); /* arbitrary */

        port->membase = (unsigned char __iomem *) __pa(port);

        port->irq = op->irqs[0];

        port->dev = &op->dev;

        err = sunserial_register_minors(&sunhv_reg, 1);
        if (err)
                goto out_free_con_read_page;

        sunserial_console_match(&sunhv_console, op->node,
                                &sunhv_reg, port->line);

        err = uart_add_one_port(&sunhv_reg, port);
        if (err)
                goto out_unregister_driver;

        err = request_irq(port->irq, sunhv_interrupt, 0, "hvcons", port);
        if (err)
                goto out_remove_port;

        dev_set_drvdata(&op->dev, port);

        return 0;

out_remove_port:
        uart_remove_one_port(&sunhv_reg, port);

out_unregister_driver:
        sunserial_unregister_minors(&sunhv_reg, 1);

out_free_con_read_page:
        kfree(con_read_page);

out_free_con_write_page:
        kfree(con_write_page);

out_free_port:
        kfree(port);
        sunhv_port = NULL;
        return err;
}

static int __devexit hv_remove(struct of_device *dev)
{
        struct uart_port *port = dev_get_drvdata(&dev->dev);

        free_irq(port->irq, port);

        uart_remove_one_port(&sunhv_reg, port);

        sunserial_unregister_minors(&sunhv_reg, 1);

        kfree(port);
        sunhv_port = NULL;

        dev_set_drvdata(&dev->dev, NULL);

        return 0;
}

static struct of_device_id hv_match[] = {
        {
                .name = "console",
                .compatible = "qcn",
        },
        {
                .name = "console",
                .compatible = "SUNW,sun4v-console",
        },
        {},
};
MODULE_DEVICE_TABLE(of, hv_match);

static struct of_platform_driver hv_driver = {
        .name           = "hv",
        .match_table    = hv_match,
        .probe          = hv_probe,
        .remove         = __devexit_p(hv_remove),
};

static int __init sunhv_init(void)
{
        if (tlb_type != hypervisor)
                return -ENODEV;

        return of_register_driver(&hv_driver, &of_bus_type);
}

static void __exit sunhv_exit(void)
{
        of_unregister_driver(&hv_driver);
}

module_init(sunhv_init);
module_exit(sunhv_exit);

MODULE_AUTHOR("David S. Miller");
MODULE_DESCRIPTION("SUN4V Hypervisor console driver");
MODULE_VERSION("2.0");
MODULE_LICENSE("GPL");