ar933x_uart.c

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/*
 *  Atheros AR933X SoC built-in UART driver
 *
 *  Copyright (C) 2011 Gabor Juhos <[email protected]>
 *
 *  Based on drivers/char/serial.c, by Linus Torvalds, Theodore Ts'o.
 *
 *  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.
 */

#include <linux/module.h>
#include <linux/ioport.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/sysrq.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/serial_core.h>
#include <linux/serial.h>
#include <linux/slab.h>
#include <linux/io.h>
#include <linux/irq.h>

#include <asm/mach-ath79/ar933x_uart.h>
#include <asm/mach-ath79/ar933x_uart_platform.h>

#define DRIVER_NAME "ar933x-uart"

#define AR933X_DUMMY_STATUS_RD  0x01

static struct uart_driver ar933x_uart_driver;

struct ar933x_uart_port {
    struct uart_port    port;
    unsigned int        ier;    /* shadow Interrupt Enable Register */
};

static inline unsigned int ar933x_uart_read(struct ar933x_uart_port *up,
                        int offset)
{
    return readl(up->port.membase + offset);
}

static inline void ar933x_uart_write(struct ar933x_uart_port *up,
                     int offset, unsigned int value)
{
    writel(value, up->port.membase + offset);
}

static inline void ar933x_uart_rmw(struct ar933x_uart_port *up,
                  unsigned int offset,
                  unsigned int mask,
                  unsigned int val)
{
    unsigned int t;

    t = ar933x_uart_read(up, offset);
    t &= ~mask;
    t |= val;
    ar933x_uart_write(up, offset, t);
}

static inline void ar933x_uart_rmw_set(struct ar933x_uart_port *up,
                       unsigned int offset,
                       unsigned int val)
{
    ar933x_uart_rmw(up, offset, 0, val);
}

static inline void ar933x_uart_rmw_clear(struct ar933x_uart_port *up,
                     unsigned int offset,
                     unsigned int val)
{
    ar933x_uart_rmw(up, offset, val, 0);
}

static inline void ar933x_uart_start_tx_interrupt(struct ar933x_uart_port *up)
{
    up->ier |= AR933X_UART_INT_TX_EMPTY;
    ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
}

static inline void ar933x_uart_stop_tx_interrupt(struct ar933x_uart_port *up)
{
    up->ier &= ~AR933X_UART_INT_TX_EMPTY;
    ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
}

static inline void ar933x_uart_putc(struct ar933x_uart_port *up, int ch)
{
    unsigned int rdata;

    rdata = ch & AR933X_UART_DATA_TX_RX_MASK;
    rdata |= AR933X_UART_DATA_TX_CSR;
    ar933x_uart_write(up, AR933X_UART_DATA_REG, rdata);
}

static unsigned int ar933x_uart_tx_empty(struct uart_port *port)
{
    struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
    unsigned long flags;
    unsigned int rdata;

    spin_lock_irqsave(&up->port.lock, flags);
    rdata = ar933x_uart_read(up, AR933X_UART_DATA_REG);
    spin_unlock_irqrestore(&up->port.lock, flags);

    return (rdata & AR933X_UART_DATA_TX_CSR) ? 0 : TIOCSER_TEMT;
}

static unsigned int ar933x_uart_get_mctrl(struct uart_port *port)
{
    return TIOCM_CAR;
}

static void ar933x_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
}

static void ar933x_uart_start_tx(struct uart_port *port)
{
    struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;

    ar933x_uart_start_tx_interrupt(up);
}

static void ar933x_uart_stop_tx(struct uart_port *port)
{
    struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;

    ar933x_uart_stop_tx_interrupt(up);
}

static void ar933x_uart_stop_rx(struct uart_port *port)
{
    struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;

    up->ier &= ~AR933X_UART_INT_RX_VALID;
    ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
}

static void ar933x_uart_break_ctl(struct uart_port *port, int break_state)
{
    struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
    unsigned long flags;

    spin_lock_irqsave(&up->port.lock, flags);
    if (break_state == -1)
        ar933x_uart_rmw_set(up, AR933X_UART_CS_REG,
                    AR933X_UART_CS_TX_BREAK);
    else
        ar933x_uart_rmw_clear(up, AR933X_UART_CS_REG,
                      AR933X_UART_CS_TX_BREAK);
    spin_unlock_irqrestore(&up->port.lock, flags);
}

static void ar933x_uart_enable_ms(struct uart_port *port)
{
}

static void ar933x_uart_set_termios(struct uart_port *port,
                    struct ktermios *new,
                    struct ktermios *old)
{
    struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
    unsigned int cs;
    unsigned long flags;
    unsigned int baud, scale;

    /* Only CS8 is supported */
    new->c_cflag &= ~CSIZE;
    new->c_cflag |= CS8;

    /* Only one stop bit is supported */
    new->c_cflag &= ~CSTOPB;

    cs = 0;
    if (new->c_cflag & PARENB) {
        if (!(new->c_cflag & PARODD))
            cs |= AR933X_UART_CS_PARITY_EVEN;
        else
            cs |= AR933X_UART_CS_PARITY_ODD;
    } else {
        cs |= AR933X_UART_CS_PARITY_NONE;
    }

    /* Mark/space parity is not supported */
    new->c_cflag &= ~CMSPAR;

    baud = uart_get_baud_rate(port, new, old, 0, port->uartclk / 16);
    scale = (port->uartclk / (16 * baud)) - 1;

    /*
     * Ok, we're now changing the port state. Do it with
     * interrupts disabled.
     */
    spin_lock_irqsave(&up->port.lock, flags);

    /* Update the per-port timeout. */
    uart_update_timeout(port, new->c_cflag, baud);

    up->port.ignore_status_mask = 0;

    /* ignore all characters if CREAD is not set */
    if ((new->c_cflag & CREAD) == 0)
        up->port.ignore_status_mask |= AR933X_DUMMY_STATUS_RD;

    ar933x_uart_write(up, AR933X_UART_CLOCK_REG,
              scale << AR933X_UART_CLOCK_SCALE_S | 8192);

    /* setup configuration register */
    ar933x_uart_rmw(up, AR933X_UART_CS_REG, AR933X_UART_CS_PARITY_M, cs);

    /* enable host interrupt */
    ar933x_uart_rmw_set(up, AR933X_UART_CS_REG,
                AR933X_UART_CS_HOST_INT_EN);

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

    if (tty_termios_baud_rate(new))
        tty_termios_encode_baud_rate(new, baud, baud);
}

static void ar933x_uart_rx_chars(struct ar933x_uart_port *up)
{
    struct tty_struct *tty;
    int max_count = 256;

    tty = tty_port_tty_get(&up->port.state->port);
    do {
        unsigned int rdata;
        unsigned char ch;

        rdata = ar933x_uart_read(up, AR933X_UART_DATA_REG);
        if ((rdata & AR933X_UART_DATA_RX_CSR) == 0)
            break;

        /* remove the character from the FIFO */
        ar933x_uart_write(up, AR933X_UART_DATA_REG,
                  AR933X_UART_DATA_RX_CSR);

        if (!tty) {
            /* discard the data if no tty available */
            continue;
        }

        up->port.icount.rx++;
        ch = rdata & AR933X_UART_DATA_TX_RX_MASK;

        if (uart_handle_sysrq_char(&up->port, ch))
            continue;

        if ((up->port.ignore_status_mask & AR933X_DUMMY_STATUS_RD) == 0)
            tty_insert_flip_char(tty, ch, TTY_NORMAL);
    } while (max_count-- > 0);

    if (tty) {
        tty_flip_buffer_push(tty);
        tty_kref_put(tty);
    }
}

static void ar933x_uart_tx_chars(struct ar933x_uart_port *up)
{
    struct circ_buf *xmit = &up->port.state->xmit;
    int count;

    if (uart_tx_stopped(&up->port))
        return;

    count = up->port.fifosize;
    do {
        unsigned int rdata;

        rdata = ar933x_uart_read(up, AR933X_UART_DATA_REG);
        if ((rdata & AR933X_UART_DATA_TX_CSR) == 0)
            break;

        if (up->port.x_char) {
            ar933x_uart_putc(up, up->port.x_char);
            up->port.icount.tx++;
            up->port.x_char = 0;
            continue;
        }

        if (uart_circ_empty(xmit))
            break;

        ar933x_uart_putc(up, xmit->buf[xmit->tail]);

        xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
        up->port.icount.tx++;
    } while (--count > 0);

    if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
        uart_write_wakeup(&up->port);

    if (!uart_circ_empty(xmit))
        ar933x_uart_start_tx_interrupt(up);
}

static irqreturn_t ar933x_uart_interrupt(int irq, void *dev_id)
{
    struct ar933x_uart_port *up = dev_id;
    unsigned int status;

    status = ar933x_uart_read(up, AR933X_UART_CS_REG);
    if ((status & AR933X_UART_CS_HOST_INT) == 0)
        return IRQ_NONE;

    spin_lock(&up->port.lock);

    status = ar933x_uart_read(up, AR933X_UART_INT_REG);
    status &= ar933x_uart_read(up, AR933X_UART_INT_EN_REG);

    if (status & AR933X_UART_INT_RX_VALID) {
        ar933x_uart_write(up, AR933X_UART_INT_REG,
                  AR933X_UART_INT_RX_VALID);
        ar933x_uart_rx_chars(up);
    }

    if (status & AR933X_UART_INT_TX_EMPTY) {
        ar933x_uart_write(up, AR933X_UART_INT_REG,
                  AR933X_UART_INT_TX_EMPTY);
        ar933x_uart_stop_tx_interrupt(up);
        ar933x_uart_tx_chars(up);
    }

    spin_unlock(&up->port.lock);

    return IRQ_HANDLED;
}

static int ar933x_uart_startup(struct uart_port *port)
{
    struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;
    unsigned long flags;
    int ret;

    ret = request_irq(up->port.irq, ar933x_uart_interrupt,
              up->port.irqflags, dev_name(up->port.dev), up);
    if (ret)
        return ret;

    spin_lock_irqsave(&up->port.lock, flags);

    /* Enable HOST interrupts */
    ar933x_uart_rmw_set(up, AR933X_UART_CS_REG,
                AR933X_UART_CS_HOST_INT_EN);

    /* Enable RX interrupts */
    up->ier = AR933X_UART_INT_RX_VALID;
    ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);

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

    return 0;
}

static void ar933x_uart_shutdown(struct uart_port *port)
{
    struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;

    /* Disable all interrupts */
    up->ier = 0;
    ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);

    /* Disable break condition */
    ar933x_uart_rmw_clear(up, AR933X_UART_CS_REG,
                  AR933X_UART_CS_TX_BREAK);

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

static const char *ar933x_uart_type(struct uart_port *port)
{
    return (port->type == PORT_AR933X) ? "AR933X UART" : NULL;
}

static void ar933x_uart_release_port(struct uart_port *port)
{
    /* Nothing to release ... */
}

static int ar933x_uart_request_port(struct uart_port *port)
{
    /* UARTs always present */
    return 0;
}

static void ar933x_uart_config_port(struct uart_port *port, int flags)
{
    if (flags & UART_CONFIG_TYPE)
        port->type = PORT_AR933X;
}

static int ar933x_uart_verify_port(struct uart_port *port,
                   struct serial_struct *ser)
{
    if (ser->type != PORT_UNKNOWN &&
        ser->type != PORT_AR933X)
        return -EINVAL;

    if (ser->irq < 0 || ser->irq >= NR_IRQS)
        return -EINVAL;

    if (ser->baud_base < 28800)
        return -EINVAL;

    return 0;
}

static struct uart_ops ar933x_uart_ops = {
    .tx_empty   = ar933x_uart_tx_empty,
    .set_mctrl  = ar933x_uart_set_mctrl,
    .get_mctrl  = ar933x_uart_get_mctrl,
    .stop_tx    = ar933x_uart_stop_tx,
    .start_tx   = ar933x_uart_start_tx,
    .stop_rx    = ar933x_uart_stop_rx,
    .enable_ms  = ar933x_uart_enable_ms,
    .break_ctl  = ar933x_uart_break_ctl,
    .startup    = ar933x_uart_startup,
    .shutdown   = ar933x_uart_shutdown,
    .set_termios    = ar933x_uart_set_termios,
    .type       = ar933x_uart_type,
    .release_port   = ar933x_uart_release_port,
    .request_port   = ar933x_uart_request_port,
    .config_port    = ar933x_uart_config_port,
    .verify_port    = ar933x_uart_verify_port,
};

#ifdef CONFIG_SERIAL_AR933X_CONSOLE

static struct ar933x_uart_port *
ar933x_console_ports[CONFIG_SERIAL_AR933X_NR_UARTS];

static void ar933x_uart_wait_xmitr(struct ar933x_uart_port *up)
{
    unsigned int status;
    unsigned int timeout = 60000;

    /* Wait up to 60ms for the character(s) to be sent. */
    do {
        status = ar933x_uart_read(up, AR933X_UART_DATA_REG);
        if (--timeout == 0)
            break;
        udelay(1);
    } while ((status & AR933X_UART_DATA_TX_CSR) == 0);
}

static void ar933x_uart_console_putchar(struct uart_port *port, int ch)
{
    struct ar933x_uart_port *up = (struct ar933x_uart_port *) port;

    ar933x_uart_wait_xmitr(up);
    ar933x_uart_putc(up, ch);
}

static void ar933x_uart_console_write(struct console *co, const char *s,
                      unsigned int count)
{
    struct ar933x_uart_port *up = ar933x_console_ports[co->index];
    unsigned long flags;
    unsigned int int_en;
    int locked = 1;

    local_irq_save(flags);

    if (up->port.sysrq)
        locked = 0;
    else if (oops_in_progress)
        locked = spin_trylock(&up->port.lock);
    else
        spin_lock(&up->port.lock);

    /*
     * First save the IER then disable the interrupts
     */
    int_en = ar933x_uart_read(up, AR933X_UART_INT_EN_REG);
    ar933x_uart_write(up, AR933X_UART_INT_EN_REG, 0);

    uart_console_write(&up->port, s, count, ar933x_uart_console_putchar);

    /*
     * Finally, wait for transmitter to become empty
     * and restore the IER
     */
    ar933x_uart_wait_xmitr(up);
    ar933x_uart_write(up, AR933X_UART_INT_EN_REG, int_en);

    ar933x_uart_write(up, AR933X_UART_INT_REG, AR933X_UART_INT_ALLINTS);

    if (locked)
        spin_unlock(&up->port.lock);

    local_irq_restore(flags);
}

static int ar933x_uart_console_setup(struct console *co, char *options)
{
    struct ar933x_uart_port *up;
    int baud = 115200;
    int bits = 8;
    int parity = 'n';
    int flow = 'n';

    if (co->index < 0 || co->index >= CONFIG_SERIAL_AR933X_NR_UARTS)
        return -EINVAL;

    up = ar933x_console_ports[co->index];
    if (!up)
        return -ENODEV;

    if (options)
        uart_parse_options(options, &baud, &parity, &bits, &flow);

    return uart_set_options(&up->port, co, baud, parity, bits, flow);
}

static struct console ar933x_uart_console = {
    .name       = "ttyATH",
    .write      = ar933x_uart_console_write,
    .device     = uart_console_device,
    .setup      = ar933x_uart_console_setup,
    .flags      = CON_PRINTBUFFER,
    .index      = -1,
    .data       = &ar933x_uart_driver,
};

static void ar933x_uart_add_console_port(struct ar933x_uart_port *up)
{
    ar933x_console_ports[up->port.line] = up;
}

#define AR933X_SERIAL_CONSOLE   (&ar933x_uart_console)

#else

static inline void ar933x_uart_add_console_port(struct ar933x_uart_port *up) {}

#define AR933X_SERIAL_CONSOLE   NULL

#endif /* CONFIG_SERIAL_AR933X_CONSOLE */

static struct uart_driver ar933x_uart_driver = {
    .owner      = THIS_MODULE,
    .driver_name    = DRIVER_NAME,
    .dev_name   = "ttyATH",
    .nr     = CONFIG_SERIAL_AR933X_NR_UARTS,
    .cons       = AR933X_SERIAL_CONSOLE,
};

static int __devinit ar933x_uart_probe(struct platform_device *pdev)
{
    struct ar933x_uart_platform_data *pdata;
    struct ar933x_uart_port *up;
    struct uart_port *port;
    struct resource *mem_res;
    struct resource *irq_res;
    int id;
    int ret;

    pdata = pdev->dev.platform_data;
    if (!pdata)
        return -EINVAL;

    id = pdev->id;
    if (id == -1)
        id = 0;

    if (id > CONFIG_SERIAL_AR933X_NR_UARTS)
        return -EINVAL;

    mem_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
    if (!mem_res) {
        dev_err(&pdev->dev, "no MEM resource\n");
        return -EINVAL;
    }

    irq_res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
    if (!irq_res) {
        dev_err(&pdev->dev, "no IRQ resource\n");
        return -EINVAL;
    }

    up = kzalloc(sizeof(struct ar933x_uart_port), GFP_KERNEL);
    if (!up)
        return -ENOMEM;

    port = &up->port;
    port->mapbase = mem_res->start;

    port->membase = ioremap(mem_res->start, AR933X_UART_REGS_SIZE);
    if (!port->membase) {
        ret = -ENOMEM;
        goto err_free_up;
    }

    port->line = id;
    port->irq = irq_res->start;
    port->dev = &pdev->dev;
    port->type = PORT_AR933X;
    port->iotype = UPIO_MEM32;
    port->uartclk = pdata->uartclk;

    port->regshift = 2;
    port->fifosize = AR933X_UART_FIFO_SIZE;
    port->ops = &ar933x_uart_ops;

    ar933x_uart_add_console_port(up);

    ret = uart_add_one_port(&ar933x_uart_driver, &up->port);
    if (ret)
        goto err_unmap;

    platform_set_drvdata(pdev, up);
    return 0;

err_unmap:
    iounmap(up->port.membase);
err_free_up:
    kfree(up);
    return ret;
}

static int __devexit ar933x_uart_remove(struct platform_device *pdev)
{
    struct ar933x_uart_port *up;

    up = platform_get_drvdata(pdev);
    platform_set_drvdata(pdev, NULL);

    if (up) {
        uart_remove_one_port(&ar933x_uart_driver, &up->port);
        iounmap(up->port.membase);
        kfree(up);
    }

    return 0;
}

static struct platform_driver ar933x_uart_platform_driver = {
    .probe      = ar933x_uart_probe,
    .remove     = __devexit_p(ar933x_uart_remove),
    .driver     = {
        .name       = DRIVER_NAME,
        .owner      = THIS_MODULE,
    },
};

static int __init ar933x_uart_init(void)
{
    int ret;

    ar933x_uart_driver.nr = CONFIG_SERIAL_AR933X_NR_UARTS;
    ret = uart_register_driver(&ar933x_uart_driver);
    if (ret)
        goto err_out;

    ret = platform_driver_register(&ar933x_uart_platform_driver);
    if (ret)
        goto err_unregister_uart_driver;

    return 0;

err_unregister_uart_driver:
    uart_unregister_driver(&ar933x_uart_driver);
err_out:
    return ret;
}

static void __exit ar933x_uart_exit(void)
{
    platform_driver_unregister(&ar933x_uart_platform_driver);
    uart_unregister_driver(&ar933x_uart_driver);
}

module_init(ar933x_uart_init);
module_exit(ar933x_uart_exit);

MODULE_DESCRIPTION("Atheros AR933X UART driver");
MODULE_AUTHOR("Gabor Juhos <[email protected]>");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("platform:" DRIVER_NAME);