/*
 *  Serial Port driver for a NWP uart device
 *
 *    Copyright (C) 2008 IBM Corp., Benjamin Krill <ben@codiert.org>
 *
 *  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.
 *
 */
#include <linux/init.h>
#include <linux/export.h>
#include <linux/console.h>
#include <linux/serial.h>
#include <linux/serial_reg.h>
#include <linux/serial_core.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/irqreturn.h>
#include <linux/mutex.h>
#include <linux/of_platform.h>
#include <linux/of_device.h>
#include <linux/nwpserial.h>
#include <asm/prom.h>
#include <asm/dcr.h>

#define NWPSERIAL_NR               2

#define NWPSERIAL_STATUS_RXVALID 0x1
#define NWPSERIAL_STATUS_TXFULL  0x2

struct nwpserial_port {
        struct uart_port port;
        dcr_host_t dcr_host;
        unsigned int ier;
        unsigned int mcr;
};

static DEFINE_MUTEX(nwpserial_mutex);
static struct nwpserial_port nwpserial_ports[NWPSERIAL_NR];

static void wait_for_bits(struct nwpserial_port *up, int bits)
{
        unsigned int status, tmout = 10000;

        /* Wait up to 10ms for the character(s) to be sent. */
        do {
                status = dcr_read(up->dcr_host, UART_LSR);

                if (--tmout == 0)
                        break;
                udelay(1);
        } while ((status & bits) != bits);
}

#ifdef CONFIG_SERIAL_OF_PLATFORM_NWPSERIAL_CONSOLE
static void nwpserial_console_putchar(struct uart_port *port, int c)
{
        struct nwpserial_port *up;
        up = container_of(port, struct nwpserial_port, port);
        /* check if tx buffer is full */
        wait_for_bits(up, UART_LSR_THRE);
        dcr_write(up->dcr_host, UART_TX, c);
        up->port.icount.tx++;
}

static void
nwpserial_console_write(struct console *co, const char *s, unsigned int count)
{
        struct nwpserial_port *up = &nwpserial_ports[co->index];
        unsigned long flags;
        int locked = 1;

        if (oops_in_progress)
                locked = spin_trylock_irqsave(&up->port.lock, flags);
        else
                spin_lock_irqsave(&up->port.lock, flags);

        /* save and disable interrupt */
        up->ier = dcr_read(up->dcr_host, UART_IER);
        dcr_write(up->dcr_host, UART_IER, up->ier & ~UART_IER_RDI);

        uart_console_write(&up->port, s, count, nwpserial_console_putchar);

        /* wait for transmitter to become empty */
        while ((dcr_read(up->dcr_host, UART_LSR) & UART_LSR_THRE) == 0)
                cpu_relax();

        /* restore interrupt state */
        dcr_write(up->dcr_host, UART_IER, up->ier);

        if (locked)
                spin_unlock_irqrestore(&up->port.lock, flags);
}

static struct uart_driver nwpserial_reg;
static struct console nwpserial_console = {
        .name           = "ttySQ",
        .write          = nwpserial_console_write,
        .device         = uart_console_device,
        .flags          = CON_PRINTBUFFER,
        .index          = -1,
        .data           = &nwpserial_reg,
};
#define NWPSERIAL_CONSOLE       (&nwpserial_console)
#else
#define NWPSERIAL_CONSOLE       NULL
#endif /* CONFIG_SERIAL_OF_PLATFORM_NWPSERIAL_CONSOLE */

/**************************************************************************/

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

static void nwpserial_release_port(struct uart_port *port)
{
        /* N/A */
}

static void nwpserial_config_port(struct uart_port *port, int flags)
{
        port->type = PORT_NWPSERIAL;
}

static irqreturn_t nwpserial_interrupt(int irq, void *dev_id)
{
        struct nwpserial_port *up = dev_id;
        struct tty_struct *tty = up->port.state->port.tty;
        irqreturn_t ret;
        unsigned int iir;
        unsigned char ch;

        spin_lock(&up->port.lock);

        /* check if the uart was the interrupt source. */
        iir = dcr_read(up->dcr_host, UART_IIR);
        if (!iir) {
                ret = IRQ_NONE;
                goto out;
        }

        do {
                up->port.icount.rx++;
                ch = dcr_read(up->dcr_host, UART_RX);
                if (up->port.ignore_status_mask != NWPSERIAL_STATUS_RXVALID)
                        tty_insert_flip_char(tty, ch, TTY_NORMAL);
        } while (dcr_read(up->dcr_host, UART_LSR) & UART_LSR_DR);

        tty_flip_buffer_push(tty);
        ret = IRQ_HANDLED;

        /* clear interrupt */
        dcr_write(up->dcr_host, UART_IIR, 1);
out:
        spin_unlock(&up->port.lock);
        return ret;
}

static int nwpserial_startup(struct uart_port *port)
{
        struct nwpserial_port *up;
        int err;

        up = container_of(port, struct nwpserial_port, port);

        /* disable flow control by default */
        up->mcr = dcr_read(up->dcr_host, UART_MCR) & ~UART_MCR_AFE;
        dcr_write(up->dcr_host, UART_MCR, up->mcr);

        /* register interrupt handler */
        err = request_irq(up->port.irq, nwpserial_interrupt,
                        IRQF_SHARED, "nwpserial", up);
        if (err)
                return err;

        /* enable interrupts */
        up->ier = UART_IER_RDI;
        dcr_write(up->dcr_host, UART_IER, up->ier);

        /* enable receiving */
        up->port.ignore_status_mask &= ~NWPSERIAL_STATUS_RXVALID;

        return 0;
}

static void nwpserial_shutdown(struct uart_port *port)
{
        struct nwpserial_port *up;
        up = container_of(port, struct nwpserial_port, port);

        /* disable receiving */
        up->port.ignore_status_mask |= NWPSERIAL_STATUS_RXVALID;

        /* disable interrupts from this port */
        up->ier = 0;
        dcr_write(up->dcr_host, UART_IER, up->ier);

        /* free irq */
        free_irq(up->port.irq, port);
}

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

static const char *nwpserial_type(struct uart_port *port)
{
        return port->type == PORT_NWPSERIAL ? "nwpserial" : NULL;
}

static void nwpserial_set_termios(struct uart_port *port,
                        struct ktermios *termios, struct ktermios *old)
{
        struct nwpserial_port *up;
        up = container_of(port, struct nwpserial_port, port);

        up->port.read_status_mask = NWPSERIAL_STATUS_RXVALID
                                | NWPSERIAL_STATUS_TXFULL;

        up->port.ignore_status_mask = 0;
        /* ignore all characters if CREAD is not set */
        if ((termios->c_cflag & CREAD) == 0)
                up->port.ignore_status_mask |= NWPSERIAL_STATUS_RXVALID;

        /* Copy back the old hardware settings */
        if (old)
                tty_termios_copy_hw(termios, old);
}

static void nwpserial_break_ctl(struct uart_port *port, int ctl)
{
        /* N/A */
}

static void nwpserial_enable_ms(struct uart_port *port)
{
        /* N/A */
}

static void nwpserial_stop_rx(struct uart_port *port)
{
        struct nwpserial_port *up;
        up = container_of(port, struct nwpserial_port, port);
        /* don't forward any more data (like !CREAD) */
        up->port.ignore_status_mask = NWPSERIAL_STATUS_RXVALID;
}

static void nwpserial_putchar(struct nwpserial_port *up, unsigned char c)
{
        /* check if tx buffer is full */
        wait_for_bits(up, UART_LSR_THRE);
        dcr_write(up->dcr_host, UART_TX, c);
        up->port.icount.tx++;
}

static void nwpserial_start_tx(struct uart_port *port)
{
        struct nwpserial_port *up;
        struct circ_buf *xmit;
        up = container_of(port, struct nwpserial_port, port);
        xmit  = &up->port.state->xmit;

        if (port->x_char) {
                nwpserial_putchar(up, up->port.x_char);
                port->x_char = 0;
        }

        while (!(uart_circ_empty(xmit) || uart_tx_stopped(&up->port))) {
                nwpserial_putchar(up, xmit->buf[xmit->tail]);
                xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE-1);
        }
}

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

static void nwpserial_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
        /* N/A */
}

static void nwpserial_stop_tx(struct uart_port *port)
{
        /* N/A */
}

static unsigned int nwpserial_tx_empty(struct uart_port *port)
{
        struct nwpserial_port *up;
        unsigned long flags;
        int ret;
        up = container_of(port, struct nwpserial_port, port);

        spin_lock_irqsave(&up->port.lock, flags);
        ret = dcr_read(up->dcr_host, UART_LSR);
        spin_unlock_irqrestore(&up->port.lock, flags);

        return ret & UART_LSR_TEMT ? TIOCSER_TEMT : 0;
}

static struct uart_ops nwpserial_pops = {
        .tx_empty     = nwpserial_tx_empty,
        .set_mctrl    = nwpserial_set_mctrl,
        .get_mctrl    = nwpserial_get_mctrl,
        .stop_tx      = nwpserial_stop_tx,
        .start_tx     = nwpserial_start_tx,
        .stop_rx      = nwpserial_stop_rx,
        .enable_ms    = nwpserial_enable_ms,
        .break_ctl    = nwpserial_break_ctl,
        .startup      = nwpserial_startup,
        .shutdown     = nwpserial_shutdown,
        .set_termios  = nwpserial_set_termios,
        .type         = nwpserial_type,
        .release_port = nwpserial_release_port,
        .request_port = nwpserial_request_port,
        .config_port  = nwpserial_config_port,
        .verify_port  = nwpserial_verify_port,
};

static struct uart_driver nwpserial_reg = {
        .owner       = THIS_MODULE,
        .driver_name = "nwpserial",
        .dev_name    = "ttySQ",
        .major       = TTY_MAJOR,
        .minor       = 68,
        .nr          = NWPSERIAL_NR,
        .cons        = NWPSERIAL_CONSOLE,
};

int nwpserial_register_port(struct uart_port *port)
{
        struct nwpserial_port *up = NULL;
        int ret = -1;
        int i;
        static int first = 1;
        int dcr_len;
        int dcr_base;
        struct device_node *dn;

        mutex_lock(&nwpserial_mutex);

        dn = port->dev->of_node;
        if (dn == NULL)
                goto out;

        /* get dcr base. */
        dcr_base = dcr_resource_start(dn, 0);

        /* find matching entry */
        for (i = 0; i < NWPSERIAL_NR; i++)
                if (nwpserial_ports[i].port.iobase == dcr_base) {
                        up = &nwpserial_ports[i];
                        break;
                }

        /* we didn't find a mtching entry, search for a free port */
        if (up == NULL)
                for (i = 0; i < NWPSERIAL_NR; i++)
                        if (nwpserial_ports[i].port.type == PORT_UNKNOWN &&
                                nwpserial_ports[i].port.iobase == 0) {
                                up = &nwpserial_ports[i];
                                break;
                        }

        if (up == NULL) {
                ret = -EBUSY;
                goto out;
        }

        if (first)
                uart_register_driver(&nwpserial_reg);
        first = 0;

        up->port.membase      = port->membase;
        up->port.irq          = port->irq;
        up->port.uartclk      = port->uartclk;
        up->port.fifosize     = port->fifosize;
        up->port.regshift     = port->regshift;
        up->port.iotype       = port->iotype;
        up->port.flags        = port->flags;
        up->port.mapbase      = port->mapbase;
        up->port.private_data = port->private_data;

        if (port->dev)
                up->port.dev = port->dev;

        if (up->port.iobase != dcr_base) {
                up->port.ops          = &nwpserial_pops;
                up->port.fifosize     = 16;

                spin_lock_init(&up->port.lock);

                up->port.iobase = dcr_base;
                dcr_len = dcr_resource_len(dn, 0);

                up->dcr_host = dcr_map(dn, dcr_base, dcr_len);
                if (!DCR_MAP_OK(up->dcr_host)) {
                        printk(KERN_ERR "Cannot map DCR resources for NWPSERIAL");
                        goto out;
                }
        }

        ret = uart_add_one_port(&nwpserial_reg, &up->port);
        if (ret == 0)
                ret = up->port.line;

out:
        mutex_unlock(&nwpserial_mutex);

        return ret;
}
EXPORT_SYMBOL(nwpserial_register_port);

void nwpserial_unregister_port(int line)
{
        struct nwpserial_port *up = &nwpserial_ports[line];
        mutex_lock(&nwpserial_mutex);
        uart_remove_one_port(&nwpserial_reg, &up->port);

        up->port.type = PORT_UNKNOWN;

        mutex_unlock(&nwpserial_mutex);
}
EXPORT_SYMBOL(nwpserial_unregister_port);

#ifdef CONFIG_SERIAL_OF_PLATFORM_NWPSERIAL_CONSOLE
static int __init nwpserial_console_init(void)
{
        struct nwpserial_port *up = NULL;
        struct device_node *dn;
        const char *name;
        int dcr_base;
        int dcr_len;
        int i;

        /* search for a free port */
        for (i = 0; i < NWPSERIAL_NR; i++)
                if (nwpserial_ports[i].port.type == PORT_UNKNOWN) {
                        up = &nwpserial_ports[i];
                        break;
                }

        if (up == NULL)
                return -1;

        name = of_get_property(of_chosen, "linux,stdout-path", NULL);
        if (name == NULL)
                return -1;

        dn = of_find_node_by_path(name);
        if (!dn)
                return -1;

        spin_lock_init(&up->port.lock);
        up->port.ops = &nwpserial_pops;
        up->port.type = PORT_NWPSERIAL;
        up->port.fifosize = 16;

        dcr_base = dcr_resource_start(dn, 0);
        dcr_len = dcr_resource_len(dn, 0);
        up->port.iobase = dcr_base;

        up->dcr_host = dcr_map(dn, dcr_base, dcr_len);
        if (!DCR_MAP_OK(up->dcr_host)) {
                printk("Cannot map DCR resources for SERIAL");
                return -1;
        }
        register_console(&nwpserial_console);
        return 0;
}
console_initcall(nwpserial_console_init);
#endif /* CONFIG_SERIAL_OF_PLATFORM_NWPSERIAL_CONSOLE */