timbuart.c

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/*
 * 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_struct *tty = port->state->port.tty;

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

    spin_unlock(&port->lock);
    tty_flip_buffer_push(port->state->port.tty);
    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__);
}

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__);
}

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_enable_ms(struct uart_port *port)
{
    /* N/A */
}

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);
}

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,
    .enable_ms = timbuart_enable_ms,
    .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 __devinit 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 __devexit 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",
        .owner  = THIS_MODULE,
    },
    .probe      = timbuart_probe,
    .remove     = __devexit_p(timbuart_remove),
};

module_platform_driver(timbuart_platform_driver);

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