/*
 * timbuart.c timberdale FPGA UART driver
 * Copyright (c) 2009 Intel Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * 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., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

/* Supports:
 * Timberdale FPGA UART
 */

#include <linux/pci.h>
#include <linux/interrupt.h>
#include <linux/serial_core.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <linux/ioport.h>
#include <linux/slab.h>
#include <linux/module.h>

#include "timbuart.h"

struct timbuart_port {
        struct uart_port        port;
        struct tasklet_struct   tasklet;
        int                     usedma;
        u32                     last_ier;
        struct platform_device  *dev;
};

static int baudrates[] = {9600, 19200, 38400, 57600, 115200, 230400, 460800,
        921600, 1843200, 3250000};

static void timbuart_mctrl_check(struct uart_port *port, u32 isr, u32 *ier);

static irqreturn_t timbuart_handleinterrupt(int irq, void *devid);

static void timbuart_stop_rx(struct uart_port *port)
{
        /* spin lock held by upper layer, disable all RX interrupts */
        u32 ier = ioread32(port->membase + TIMBUART_IER) & ~RXFLAGS;
        iowrite32(ier, port->membase + TIMBUART_IER);
}

static void timbuart_stop_tx(struct uart_port *port)
{
        /* spinlock held by upper layer, disable TX interrupt */
        u32 ier = ioread32(port->membase + TIMBUART_IER) & ~TXBAE;
        iowrite32(ier, port->membase + TIMBUART_IER);
}

static void timbuart_start_tx(struct uart_port *port)
{
        struct timbuart_port *uart =
                container_of(port, struct timbuart_port, port);

        /* do not transfer anything here -> fire off the tasklet */
        tasklet_schedule(&uart->tasklet);
}

static unsigned int timbuart_tx_empty(struct uart_port *port)
{
        u32 isr = ioread32(port->membase + TIMBUART_ISR);

        return (isr & TXBE) ? TIOCSER_TEMT : 0;
}

static void timbuart_flush_buffer(struct uart_port *port)
{
        if (!timbuart_tx_empty(port)) {
                u8 ctl = ioread8(port->membase + TIMBUART_CTRL) |
                        TIMBUART_CTRL_FLSHTX;

                iowrite8(ctl, port->membase + TIMBUART_CTRL);
                iowrite32(TXBF, port->membase + TIMBUART_ISR);
        }
}

static void timbuart_rx_chars(struct uart_port *port)
{
        struct tty_port *tport = &port->state->port;

        while (ioread32(port->membase + TIMBUART_ISR) & RXDP) {
                u8 ch = ioread8(port->membase + TIMBUART_RXFIFO);
                port->icount.rx++;
                tty_insert_flip_char(tport, ch, TTY_NORMAL);
        }

        spin_unlock(&port->lock);
        tty_flip_buffer_push(tport);
        spin_lock(&port->lock);

        dev_dbg(port->dev, "%s - total read %d bytes\n",
                __func__, port->icount.rx);
}

static void timbuart_tx_chars(struct uart_port *port)
{
        struct circ_buf *xmit = &port->state->xmit;

        while (!(ioread32(port->membase + TIMBUART_ISR) & TXBF) &&
                !uart_circ_empty(xmit)) {
                iowrite8(xmit->buf[xmit->tail],
                        port->membase + TIMBUART_TXFIFO);
                xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
                port->icount.tx++;
        }

        dev_dbg(port->dev,
                "%s - total written %d bytes, CTL: %x, RTS: %x, baud: %x\n",
                 __func__,
                port->icount.tx,
                ioread8(port->membase + TIMBUART_CTRL),
                port->mctrl & TIOCM_RTS,
                ioread8(port->membase + TIMBUART_BAUDRATE));
}

static void timbuart_handle_tx_port(struct uart_port *port, u32 isr, u32 *ier)
{
        struct timbuart_port *uart =
                container_of(port, struct timbuart_port, port);
        struct circ_buf *xmit = &port->state->xmit;

        if (uart_circ_empty(xmit) || uart_tx_stopped(port))
                return;

        if (port->x_char)
                return;

        if (isr & TXFLAGS) {
                timbuart_tx_chars(port);
                /* clear all TX interrupts */
                iowrite32(TXFLAGS, port->membase + TIMBUART_ISR);

                if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
                        uart_write_wakeup(port);
        } else
                /* Re-enable any tx interrupt */
                *ier |= uart->last_ier & TXFLAGS;

        /* enable interrupts if there are chars in the transmit buffer,
         * Or if we delivered some bytes and want the almost empty interrupt
         * we wake up the upper layer later when we got the interrupt
         * to give it some time to go out...
         */
        if (!uart_circ_empty(xmit))
                *ier |= TXBAE;

        dev_dbg(port->dev, "%s - leaving\n", __func__);
}

static void timbuart_handle_rx_port(struct uart_port *port, u32 isr, u32 *ier)
{
        if (isr & RXFLAGS) {
                /* Some RX status is set */
                if (isr & RXBF) {
                        u8 ctl = ioread8(port->membase + TIMBUART_CTRL) |
                                TIMBUART_CTRL_FLSHRX;
                        iowrite8(ctl, port->membase + TIMBUART_CTRL);
                        port->icount.overrun++;
                } else if (isr & (RXDP))
                        timbuart_rx_chars(port);

                /* ack all RX interrupts */
                iowrite32(RXFLAGS, port->membase + TIMBUART_ISR);
        }

        /* always have the RX interrupts enabled */
        *ier |= RXBAF | RXBF | RXTT;

        dev_dbg(port->dev, "%s - leaving\n", __func__);
}

static void timbuart_tasklet(unsigned long arg)
{
        struct timbuart_port *uart = (struct timbuart_port *)arg;
        u32 isr, ier = 0;

        spin_lock(&uart->port.lock);

        isr = ioread32(uart->port.membase + TIMBUART_ISR);
        dev_dbg(uart->port.dev, "%s ISR: %x\n", __func__, isr);

        if (!uart->usedma)
                timbuart_handle_tx_port(&uart->port, isr, &ier);

        timbuart_mctrl_check(&uart->port, isr, &ier);

        if (!uart->usedma)
                timbuart_handle_rx_port(&uart->port, isr, &ier);

        iowrite32(ier, uart->port.membase + TIMBUART_IER);

        spin_unlock(&uart->port.lock);
        dev_dbg(uart->port.dev, "%s leaving\n", __func__);
}

static unsigned int timbuart_get_mctrl(struct uart_port *port)
{
        u8 cts = ioread8(port->membase + TIMBUART_CTRL);
        dev_dbg(port->dev, "%s - cts %x\n", __func__, cts);

        if (cts & TIMBUART_CTRL_CTS)
                return TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
        else
                return TIOCM_DSR | TIOCM_CAR;
}

static void timbuart_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
        dev_dbg(port->dev, "%s - %x\n", __func__, mctrl);

        if (mctrl & TIOCM_RTS)
                iowrite8(TIMBUART_CTRL_RTS, port->membase + TIMBUART_CTRL);
        else
                iowrite8(0, port->membase + TIMBUART_CTRL);
}

static void timbuart_mctrl_check(struct uart_port *port, u32 isr, u32 *ier)
{
        unsigned int cts;

        if (isr & CTS_DELTA) {
                /* ack */
                iowrite32(CTS_DELTA, port->membase + TIMBUART_ISR);
                cts = timbuart_get_mctrl(port);
                uart_handle_cts_change(port, cts & TIOCM_CTS);
                wake_up_interruptible(&port->state->port.delta_msr_wait);
        }

        *ier |= CTS_DELTA;
}

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

static int timbuart_startup(struct uart_port *port)
{
        struct timbuart_port *uart =
                container_of(port, struct timbuart_port, port);

        dev_dbg(port->dev, "%s\n", __func__);

        iowrite8(TIMBUART_CTRL_FLSHRX, port->membase + TIMBUART_CTRL);
        iowrite32(0x1ff, port->membase + TIMBUART_ISR);
        /* Enable all but TX interrupts */
        iowrite32(RXBAF | RXBF | RXTT | CTS_DELTA,
                port->membase + TIMBUART_IER);

        return request_irq(port->irq, timbuart_handleinterrupt, IRQF_SHARED,
                "timb-uart", uart);
}

static void timbuart_shutdown(struct uart_port *port)
{
        struct timbuart_port *uart =
                container_of(port, struct timbuart_port, port);
        dev_dbg(port->dev, "%s\n", __func__);
        free_irq(port->irq, uart);
        iowrite32(0, port->membase + TIMBUART_IER);

        timbuart_flush_buffer(port);
}

static int get_bindex(int baud)
{
        int i;

        for (i = 0; i < ARRAY_SIZE(baudrates); i++)
                if (baud <= baudrates[i])
                        return i;

        return -1;
}

static void timbuart_set_termios(struct uart_port *port,
        struct ktermios *termios,
        struct ktermios *old)
{
        unsigned int baud;
        short bindex;
        unsigned long flags;

        baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk / 16);
        bindex = get_bindex(baud);
        dev_dbg(port->dev, "%s - bindex %d\n", __func__, bindex);

        if (bindex < 0)
                bindex = 0;
        baud = baudrates[bindex];

        /* The serial layer calls into this once with old = NULL when setting
           up initially */
        if (old)
                tty_termios_copy_hw(termios, old);
        tty_termios_encode_baud_rate(termios, baud, baud);

        spin_lock_irqsave(&port->lock, flags);
        iowrite8((u8)bindex, port->membase + TIMBUART_BAUDRATE);
        uart_update_timeout(port, termios->c_cflag, baud);
        spin_unlock_irqrestore(&port->lock, flags);
}

static const char *timbuart_type(struct uart_port *port)
{
        return port->type == PORT_UNKNOWN ? "timbuart" : NULL;
}

/* We do not request/release mappings of the registers here,
 * currently it's done in the proble function.
 */
static void timbuart_release_port(struct uart_port *port)
{
        struct platform_device *pdev = to_platform_device(port->dev);
        int size =
                resource_size(platform_get_resource(pdev, IORESOURCE_MEM, 0));

        if (port->flags & UPF_IOREMAP) {
                iounmap(port->membase);
                port->membase = NULL;
        }

        release_mem_region(port->mapbase, size);
}

static int timbuart_request_port(struct uart_port *port)
{
        struct platform_device *pdev = to_platform_device(port->dev);
        int size =
                resource_size(platform_get_resource(pdev, IORESOURCE_MEM, 0));

        if (!request_mem_region(port->mapbase, size, "timb-uart"))
                return -EBUSY;

        if (port->flags & UPF_IOREMAP) {
                port->membase = ioremap(port->mapbase, size);
                if (port->membase == NULL) {
                        release_mem_region(port->mapbase, size);
                        return -ENOMEM;
                }
        }

        return 0;
}

static irqreturn_t timbuart_handleinterrupt(int irq, void *devid)
{
        struct timbuart_port *uart = (struct timbuart_port *)devid;

        if (ioread8(uart->port.membase + TIMBUART_IPR)) {
                uart->last_ier = ioread32(uart->port.membase + TIMBUART_IER);

                /* disable interrupts, the tasklet enables them again */
                iowrite32(0, uart->port.membase + TIMBUART_IER);

                /* fire off bottom half */
                tasklet_schedule(&uart->tasklet);

                return IRQ_HANDLED;
        } else
                return IRQ_NONE;
}

/*
 * Configure/autoconfigure the port.
 */
static void timbuart_config_port(struct uart_port *port, int flags)
{
        if (flags & UART_CONFIG_TYPE) {
                port->type = PORT_TIMBUART;
                timbuart_request_port(port);
        }
}

static int timbuart_verify_port(struct uart_port *port,
        struct serial_struct *ser)
{
        /* we don't want the core code to modify any port params */
        return -EINVAL;
}

static struct uart_ops timbuart_ops = {
        .tx_empty = timbuart_tx_empty,
        .set_mctrl = timbuart_set_mctrl,
        .get_mctrl = timbuart_get_mctrl,
        .stop_tx = timbuart_stop_tx,
        .start_tx = timbuart_start_tx,
        .flush_buffer = timbuart_flush_buffer,
        .stop_rx = timbuart_stop_rx,
        .break_ctl = timbuart_break_ctl,
        .startup = timbuart_startup,
        .shutdown = timbuart_shutdown,
        .set_termios = timbuart_set_termios,
        .type = timbuart_type,
        .release_port = timbuart_release_port,
        .request_port = timbuart_request_port,
        .config_port = timbuart_config_port,
        .verify_port = timbuart_verify_port
};

static struct uart_driver timbuart_driver = {
        .owner = THIS_MODULE,
        .driver_name = "timberdale_uart",
        .dev_name = "ttyTU",
        .major = TIMBUART_MAJOR,
        .minor = TIMBUART_MINOR,
        .nr = 1
};

static int timbuart_probe(struct platform_device *dev)
{
        int err, irq;
        struct timbuart_port *uart;
        struct resource *iomem;

        dev_dbg(&dev->dev, "%s\n", __func__);

        uart = kzalloc(sizeof(*uart), GFP_KERNEL);
        if (!uart) {
                err = -EINVAL;
                goto err_mem;
        }

        uart->usedma = 0;

        uart->port.uartclk = 3250000 * 16;
        uart->port.fifosize  = TIMBUART_FIFO_SIZE;
        uart->port.regshift  = 2;
        uart->port.iotype  = UPIO_MEM;
        uart->port.ops = &timbuart_ops;
        uart->port.irq = 0;
        uart->port.flags = UPF_BOOT_AUTOCONF | UPF_IOREMAP;
        uart->port.line  = 0;
        uart->port.dev  = &dev->dev;

        iomem = platform_get_resource(dev, IORESOURCE_MEM, 0);
        if (!iomem) {
                err = -ENOMEM;
                goto err_register;
        }
        uart->port.mapbase = iomem->start;
        uart->port.membase = NULL;

        irq = platform_get_irq(dev, 0);
        if (irq < 0) {
                err = -EINVAL;
                goto err_register;
        }
        uart->port.irq = irq;

        tasklet_init(&uart->tasklet, timbuart_tasklet, (unsigned long)uart);

        err = uart_register_driver(&timbuart_driver);
        if (err)
                goto err_register;

        err = uart_add_one_port(&timbuart_driver, &uart->port);
        if (err)
                goto err_add_port;

        platform_set_drvdata(dev, uart);

        return 0;

err_add_port:
        uart_unregister_driver(&timbuart_driver);
err_register:
        kfree(uart);
err_mem:
        printk(KERN_ERR "timberdale: Failed to register Timberdale UART: %d\n",
                err);

        return err;
}

static int timbuart_remove(struct platform_device *dev)
{
        struct timbuart_port *uart = platform_get_drvdata(dev);

        tasklet_kill(&uart->tasklet);
        uart_remove_one_port(&timbuart_driver, &uart->port);
        uart_unregister_driver(&timbuart_driver);
        kfree(uart);

        return 0;
}

static struct platform_driver timbuart_platform_driver = {
        .driver = {
                .name   = "timb-uart",
        },
        .probe          = timbuart_probe,
        .remove         = timbuart_remove,
};

module_platform_driver(timbuart_platform_driver);

MODULE_DESCRIPTION("Timberdale UART driver");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:timb-uart");