[CPUFREQ] Fix the p4-clockmod N60 errata workaround.

[linux-2.6/mini2440.git] / drivers / serial / at91_serial.c

/*
 *  linux/drivers/char/at91_serial.c
 *
 *  Driver for Atmel AT91RM9200 Serial ports
 *
 *  Copyright (C) 2003 Rick Bronson
 *
 *  Based on drivers/char/serial_sa1100.c, by Deep Blue Solutions Ltd.
 *  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 as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */
#include <linux/config.h>
#include <linux/module.h>
#include <linux/tty.h>
#include <linux/ioport.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/serial.h>
#include <linux/console.h>
#include <linux/sysrq.h>
#include <linux/tty_flip.h>

#include <asm/io.h>

#include <asm/arch/at91rm9200_usart.h>
#include <asm/mach/serial_at91rm9200.h>
#include <asm/arch/board.h>
#include <asm/arch/pio.h>


#if defined(CONFIG_SERIAL_AT91_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
#define SUPPORT_SYSRQ
#endif

#include <linux/serial_core.h>

#ifdef CONFIG_SERIAL_AT91_TTYAT

/* Use device name ttyAT, major 204 and minor 154-169.  This is necessary if we
 * should coexist with the 8250 driver, such as if we have an external 16C550
 * UART. */
#define SERIAL_AT91_MAJOR       204
#define MINOR_START             154
#define AT91_DEVICENAME         "ttyAT"

#else

/* Use device name ttyS, major 4, minor 64-68.  This is the usual serial port
 * name, but it is legally reserved for the 8250 driver. */
#define SERIAL_AT91_MAJOR       TTY_MAJOR
#define MINOR_START             64
#define AT91_DEVICENAME         "ttyS"

#endif

#define AT91_VA_BASE_DBGU       ((unsigned long) AT91_VA_BASE_SYS + AT91_DBGU)
#define AT91_ISR_PASS_LIMIT     256

#define UART_PUT_CR(port,v)     writel(v, (port)->membase + AT91_US_CR)
#define UART_GET_MR(port)       readl((port)->membase + AT91_US_MR)
#define UART_PUT_MR(port,v)     writel(v, (port)->membase + AT91_US_MR)
#define UART_PUT_IER(port,v)    writel(v, (port)->membase + AT91_US_IER)
#define UART_PUT_IDR(port,v)    writel(v, (port)->membase + AT91_US_IDR)
#define UART_GET_IMR(port)      readl((port)->membase + AT91_US_IMR)
#define UART_GET_CSR(port)      readl((port)->membase + AT91_US_CSR)
#define UART_GET_CHAR(port)     readl((port)->membase + AT91_US_RHR)
#define UART_PUT_CHAR(port,v)   writel(v, (port)->membase + AT91_US_THR)
#define UART_GET_BRGR(port)     readl((port)->membase + AT91_US_BRGR)
#define UART_PUT_BRGR(port,v)   writel(v, (port)->membase + AT91_US_BRGR)
#define UART_PUT_RTOR(port,v)   writel(v, (port)->membase + AT91_US_RTOR)

// #define UART_GET_CR(port)    readl((port)->membase + AT91_US_CR)             // is write-only

 /* PDC registers */
#define UART_PUT_PTCR(port,v)   writel(v, (port)->membase + AT91_PDC_PTCR)
#define UART_PUT_RPR(port,v)    writel(v, (port)->membase + AT91_PDC_RPR)
#define UART_PUT_RCR(port,v)    writel(v, (port)->membase + AT91_PDC_RCR)
#define UART_GET_RCR(port)      readl((port)->membase + AT91_PDC_RCR)
#define UART_PUT_RNPR(port,v)   writel(v, (port)->membase + AT91_PDC_RNPR)
#define UART_PUT_RNCR(port,v)   writel(v, (port)->membase + AT91_PDC_RNCR)


static int (*at91_open)(struct uart_port *);
static void (*at91_close)(struct uart_port *);

#ifdef SUPPORT_SYSRQ
static struct console at91_console;
#endif

/*
 * Return TIOCSER_TEMT when transmitter FIFO and Shift register is empty.
 */
static u_int at91_tx_empty(struct uart_port *port)
{
        return (UART_GET_CSR(port) & AT91_US_TXEMPTY) ? TIOCSER_TEMT : 0;
}

/*
 * Set state of the modem control output lines
 */
static void at91_set_mctrl(struct uart_port *port, u_int mctrl)
{
        unsigned int control = 0;

        /*
         * Errata #39: RTS0 is not internally connected to PA21.  We need to drive
         *  the pin manually.
         */
        if (port->mapbase == AT91_VA_BASE_US0) {
                if (mctrl & TIOCM_RTS)
                        at91_sys_write(AT91_PIOA + PIO_CODR, AT91_PA21_RTS0);
                else
                        at91_sys_write(AT91_PIOA + PIO_SODR, AT91_PA21_RTS0);
        }

        if (mctrl & TIOCM_RTS)
                control |= AT91_US_RTSEN;
        else
                control |= AT91_US_RTSDIS;

        if (mctrl & TIOCM_DTR)
                control |= AT91_US_DTREN;
        else
                control |= AT91_US_DTRDIS;

        UART_PUT_CR(port,control);
}

/*
 * Get state of the modem control input lines
 */
static u_int at91_get_mctrl(struct uart_port *port)
{
        unsigned int status, ret = 0;

        status = UART_GET_CSR(port);

        /*
         * The control signals are active low.
         */
        if (!(status & AT91_US_DCD))
                ret |= TIOCM_CD;
        if (!(status & AT91_US_CTS))
                ret |= TIOCM_CTS;
        if (!(status & AT91_US_DSR))
                ret |= TIOCM_DSR;
        if (!(status & AT91_US_RI))
                ret |= TIOCM_RI;

        return ret;
}

/*
 * Stop transmitting.
 */
static void at91_stop_tx(struct uart_port *port)
{
        UART_PUT_IDR(port, AT91_US_TXRDY);
        port->read_status_mask &= ~AT91_US_TXRDY;
}

/*
 * Start transmitting.
 */
static void at91_start_tx(struct uart_port *port)
{
        port->read_status_mask |= AT91_US_TXRDY;
        UART_PUT_IER(port, AT91_US_TXRDY);
}

/*
 * Stop receiving - port is in process of being closed.
 */
static void at91_stop_rx(struct uart_port *port)
{
        UART_PUT_IDR(port, AT91_US_RXRDY);
}

/*
 * Enable modem status interrupts
 */
static void at91_enable_ms(struct uart_port *port)
{
        port->read_status_mask |= (AT91_US_RIIC | AT91_US_DSRIC | AT91_US_DCDIC | AT91_US_CTSIC);
        UART_PUT_IER(port, AT91_US_RIIC | AT91_US_DSRIC | AT91_US_DCDIC | AT91_US_CTSIC);
}

/*
 * Control the transmission of a break signal
 */
static void at91_break_ctl(struct uart_port *port, int break_state)
{
        if (break_state != 0)
                UART_PUT_CR(port, AT91_US_STTBRK);      /* start break */
        else
                UART_PUT_CR(port, AT91_US_STPBRK);      /* stop break */
}

/*
 * Characters received (called from interrupt handler)
 */
static void at91_rx_chars(struct uart_port *port, struct pt_regs *regs)
{
        struct tty_struct *tty = port->info->tty;
        unsigned int status, ch, flg;

        status = UART_GET_CSR(port) & port->read_status_mask;
        while (status & (AT91_US_RXRDY)) {
                ch = UART_GET_CHAR(port);

                port->icount.rx++;

                flg = TTY_NORMAL;

                /*
                 * note that the error handling code is
                 * out of the main execution path
                 */
                if (unlikely(status & (AT91_US_PARE | AT91_US_FRAME | AT91_US_OVRE))) {
                        UART_PUT_CR(port, AT91_US_RSTSTA);      /* clear error */
                        if (status & (AT91_US_PARE))
                                port->icount.parity++;
                        if (status & (AT91_US_FRAME))
                                port->icount.frame++;
                        if (status & (AT91_US_OVRE))
                                port->icount.overrun++;

                        if (status & AT91_US_PARE)
                                flg = TTY_PARITY;
                        else if (status & AT91_US_FRAME)
                                flg = TTY_FRAME;
                        if (status & AT91_US_OVRE) {
                                /*
                                 * overrun does *not* affect the character
                                 * we read from the FIFO
                                 */
                                tty_insert_flip_char(tty, ch, flg);
                                ch = 0;
                                flg = TTY_OVERRUN;
                        }
#ifdef SUPPORT_SYSRQ
                        port->sysrq = 0;
#endif
                }

                if (uart_handle_sysrq_char(port, ch, regs))
                        goto ignore_char;

                tty_insert_flip_char(tty, ch, flg);

        ignore_char:
                status = UART_GET_CSR(port) & port->read_status_mask;
        }

        tty_flip_buffer_push(tty);
}

/*
 * Transmit characters (called from interrupt handler)
 */
static void at91_tx_chars(struct uart_port *port)
{
        struct circ_buf *xmit = &port->info->xmit;

        if (port->x_char) {
                UART_PUT_CHAR(port, port->x_char);
                port->icount.tx++;
                port->x_char = 0;
                return;
        }
        if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
                at91_stop_tx(port);
                return;
        }

        while (UART_GET_CSR(port) & AT91_US_TXRDY) {
                UART_PUT_CHAR(port, xmit->buf[xmit->tail]);
                xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
                port->icount.tx++;
                if (uart_circ_empty(xmit))
                        break;
        }

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

        if (uart_circ_empty(xmit))
                at91_stop_tx(port);
}

/*
 * Interrupt handler
 */
static irqreturn_t at91_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
        struct uart_port *port = dev_id;
        unsigned int status, pending, pass_counter = 0;

        status = UART_GET_CSR(port);
        pending = status & port->read_status_mask;
        if (pending) {
                do {
                        if (pending & AT91_US_RXRDY)
                                at91_rx_chars(port, regs);

                        /* Clear the relevent break bits */
                        if (pending & AT91_US_RXBRK) {
                                UART_PUT_CR(port, AT91_US_RSTSTA);
                                port->icount.brk++;
                                uart_handle_break(port);
                        }

                        // TODO: All reads to CSR will clear these interrupts!
                        if (pending & AT91_US_RIIC) port->icount.rng++;
                        if (pending & AT91_US_DSRIC) port->icount.dsr++;
                        if (pending & AT91_US_DCDIC)
                                uart_handle_dcd_change(port, !(status & AT91_US_DCD));
                        if (pending & AT91_US_CTSIC)
                                uart_handle_cts_change(port, !(status & AT91_US_CTS));
                        if (pending & (AT91_US_RIIC | AT91_US_DSRIC | AT91_US_DCDIC | AT91_US_CTSIC))
                                wake_up_interruptible(&port->info->delta_msr_wait);

                        if (pending & AT91_US_TXRDY)
                                at91_tx_chars(port);
                        if (pass_counter++ > AT91_ISR_PASS_LIMIT)
                                break;

                        status = UART_GET_CSR(port);
                        pending = status & port->read_status_mask;
                } while (pending);
        }
        return IRQ_HANDLED;
}

/*
 * Perform initialization and enable port for reception
 */
static int at91_startup(struct uart_port *port)
{
        int retval;

        /*
         * Ensure that no interrupts are enabled otherwise when
         * request_irq() is called we could get stuck trying to
         * handle an unexpected interrupt
         */
        UART_PUT_IDR(port, -1);

        /*
         * Allocate the IRQ
         */
        retval = request_irq(port->irq, at91_interrupt, SA_SHIRQ, "at91_serial", port);
        if (retval) {
                printk("at91_serial: at91_startup - Can't get irq\n");
                return retval;
        }

        /*
         * If there is a specific "open" function (to register
         * control line interrupts)
         */
        if (at91_open) {
                retval = at91_open(port);
                if (retval) {
                        free_irq(port->irq, port);
                        return retval;
                }
        }

        port->read_status_mask = AT91_US_RXRDY | AT91_US_TXRDY | AT91_US_OVRE
                        | AT91_US_FRAME | AT91_US_PARE | AT91_US_RXBRK;
        /*
         * Finally, enable the serial port
         */
        UART_PUT_CR(port, AT91_US_RSTSTA | AT91_US_RSTRX);
        UART_PUT_CR(port, AT91_US_TXEN | AT91_US_RXEN);         /* enable xmit & rcvr */
        UART_PUT_IER(port, AT91_US_RXRDY);                      /* do receive only */
        return 0;
}

/*
 * Disable the port
 */
static void at91_shutdown(struct uart_port *port)
{
        /*
         * Disable all interrupts, port and break condition.
         */
        UART_PUT_CR(port, AT91_US_RSTSTA);
        UART_PUT_IDR(port, -1);

        /*
         * Free the interrupt
         */
        free_irq(port->irq, port);

        /*
         * If there is a specific "close" function (to unregister
         * control line interrupts)
         */
        if (at91_close)
                at91_close(port);
}

/*
 * Power / Clock management.
 */
static void at91_serial_pm(struct uart_port *port, unsigned int state, unsigned int oldstate)
{
        switch (state) {
                case 0:
                        /*
                         * Enable the peripheral clock for this serial port.
                         * This is called on uart_open() or a resume event.
                         */
                        at91_sys_write(AT91_PMC_PCER, 1 << port->irq);
                        break;
                case 3:
                        /*
                         * Disable the peripheral clock for this serial port.
                         * This is called on uart_close() or a suspend event.
                         */
                        if (port->irq != AT91_ID_SYS)                   /* is this a shared clock? */
                                at91_sys_write(AT91_PMC_PCDR, 1 << port->irq);
                        break;
                default:
                        printk(KERN_ERR "at91_serial: unknown pm %d\n", state);
        }
}

/*
 * Change the port parameters
 */
static void at91_set_termios(struct uart_port *port, struct termios * termios, struct termios * old)
{
        unsigned long flags;
        unsigned int mode, imr, quot, baud;

        baud = uart_get_baud_rate(port, termios, old, 0, port->uartclk/16);
        quot = uart_get_divisor(port, baud);

        /* Get current mode register */
        mode = UART_GET_MR(port) & ~(AT91_US_CHRL | AT91_US_NBSTOP | AT91_US_PAR);

        /* byte size */
        switch (termios->c_cflag & CSIZE) {
        case CS5:
                mode |= AT91_US_CHRL_5;
                break;
        case CS6:
                mode |= AT91_US_CHRL_6;
                break;
        case CS7:
                mode |= AT91_US_CHRL_7;
                break;
        default:
                mode |= AT91_US_CHRL_8;
                break;
        }

        /* stop bits */
        if (termios->c_cflag & CSTOPB)
                mode |= AT91_US_NBSTOP_2;

        /* parity */
        if (termios->c_cflag & PARENB) {
                if (termios->c_cflag & CMSPAR) {                        /* Mark or Space parity */
                        if (termios->c_cflag & PARODD)
                                mode |= AT91_US_PAR_MARK;
                        else
                                mode |= AT91_US_PAR_SPACE;
                }
                else if (termios->c_cflag & PARODD)
                        mode |= AT91_US_PAR_ODD;
                else
                        mode |= AT91_US_PAR_EVEN;
        }
        else
                mode |= AT91_US_PAR_NONE;

        spin_lock_irqsave(&port->lock, flags);

        port->read_status_mask |= AT91_US_OVRE;
        if (termios->c_iflag & INPCK)
                port->read_status_mask |= AT91_US_FRAME | AT91_US_PARE;
        if (termios->c_iflag & (BRKINT | PARMRK))
                port->read_status_mask |= AT91_US_RXBRK;

        /*
         * Characters to ignore
         */
        port->ignore_status_mask = 0;
        if (termios->c_iflag & IGNPAR)
                port->ignore_status_mask |= (AT91_US_FRAME | AT91_US_PARE);
        if (termios->c_iflag & IGNBRK) {
                port->ignore_status_mask |= AT91_US_RXBRK;
                /*
                 * If we're ignoring parity and break indicators,
                 * ignore overruns too (for real raw support).
                 */
                if (termios->c_iflag & IGNPAR)
                        port->ignore_status_mask |= AT91_US_OVRE;
        }

        // TODO: Ignore all characters if CREAD is set.

        /* update the per-port timeout */
        uart_update_timeout(port, termios->c_cflag, baud);

        /* disable interrupts and drain transmitter */
        imr = UART_GET_IMR(port);       /* get interrupt mask */
        UART_PUT_IDR(port, -1);         /* disable all interrupts */
        while (!(UART_GET_CSR(port) & AT91_US_TXEMPTY)) { barrier(); }

        /* disable receiver and transmitter */
        UART_PUT_CR(port, AT91_US_TXDIS | AT91_US_RXDIS);

        /* set the parity, stop bits and data size */
        UART_PUT_MR(port, mode);

        /* set the baud rate */
        UART_PUT_BRGR(port, quot);
        UART_PUT_CR(port, AT91_US_RSTSTA | AT91_US_RSTRX);
        UART_PUT_CR(port, AT91_US_TXEN | AT91_US_RXEN);

        /* restore interrupts */
        UART_PUT_IER(port, imr);

        /* CTS flow-control and modem-status interrupts */
        if (UART_ENABLE_MS(port, termios->c_cflag))
                port->ops->enable_ms(port);

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

/*
 * Return string describing the specified port
 */
static const char *at91_type(struct uart_port *port)
{
        return (port->type == PORT_AT91RM9200) ? "AT91_SERIAL" : NULL;
}

/*
 * Release the memory region(s) being used by 'port'.
 */
static void at91_release_port(struct uart_port *port)
{
        release_mem_region(port->mapbase,
                (port->mapbase == AT91_VA_BASE_DBGU) ? 512 : SZ_16K);
}

/*
 * Request the memory region(s) being used by 'port'.
 */
static int at91_request_port(struct uart_port *port)
{
        return request_mem_region(port->mapbase,
                (port->mapbase == AT91_VA_BASE_DBGU) ? 512 : SZ_16K,
                "at91_serial") != NULL ? 0 : -EBUSY;

}

/*
 * Configure/autoconfigure the port.
 */
static void at91_config_port(struct uart_port *port, int flags)
{
        if (flags & UART_CONFIG_TYPE) {
                port->type = PORT_AT91RM9200;
                at91_request_port(port);
        }
}

/*
 * Verify the new serial_struct (for TIOCSSERIAL).
 */
static int at91_verify_port(struct uart_port *port, struct serial_struct *ser)
{
        int ret = 0;
        if (ser->type != PORT_UNKNOWN && ser->type != PORT_AT91RM9200)
                ret = -EINVAL;
        if (port->irq != ser->irq)
                ret = -EINVAL;
        if (ser->io_type != SERIAL_IO_MEM)
                ret = -EINVAL;
        if (port->uartclk / 16 != ser->baud_base)
                ret = -EINVAL;
        if ((void *)port->mapbase != ser->iomem_base)
                ret = -EINVAL;
        if (port->iobase != ser->port)
                ret = -EINVAL;
        if (ser->hub6 != 0)
                ret = -EINVAL;
        return ret;
}

static struct uart_ops at91_pops = {
        .tx_empty       = at91_tx_empty,
        .set_mctrl      = at91_set_mctrl,
        .get_mctrl      = at91_get_mctrl,
        .stop_tx        = at91_stop_tx,
        .start_tx       = at91_start_tx,
        .stop_rx        = at91_stop_rx,
        .enable_ms      = at91_enable_ms,
        .break_ctl      = at91_break_ctl,
        .startup        = at91_startup,
        .shutdown       = at91_shutdown,
        .set_termios    = at91_set_termios,
        .type           = at91_type,
        .release_port   = at91_release_port,
        .request_port   = at91_request_port,
        .config_port    = at91_config_port,
        .verify_port    = at91_verify_port,
        .pm             = at91_serial_pm,
};

static struct uart_port at91_ports[AT91_NR_UART];

void __init at91_init_ports(void)
{
        static int first = 1;
        int i;

        if (!first)
                return;
        first = 0;

        for (i = 0; i < AT91_NR_UART; i++) {
                at91_ports[i].iotype    = UPIO_MEM;
                at91_ports[i].flags     = UPF_BOOT_AUTOCONF;
                at91_ports[i].uartclk   = at91_master_clock;
                at91_ports[i].ops       = &at91_pops;
                at91_ports[i].fifosize  = 1;
                at91_ports[i].line      = i;
        }
}

void __init at91_register_uart_fns(struct at91rm9200_port_fns *fns)
{
        if (fns->enable_ms)
                at91_pops.enable_ms = fns->enable_ms;
        if (fns->get_mctrl)
                at91_pops.get_mctrl = fns->get_mctrl;
        if (fns->set_mctrl)
                at91_pops.set_mctrl = fns->set_mctrl;
        at91_open          = fns->open;
        at91_close         = fns->close;
        at91_pops.pm       = fns->pm;
        at91_pops.set_wake = fns->set_wake;
}

/*
 * Setup ports.
 */
void __init at91_register_uart(int idx, int port)
{
        if ((idx < 0) || (idx >= AT91_NR_UART)) {
                printk(KERN_ERR "%s: bad index number %d\n", __FUNCTION__, idx);
                return;
        }

        switch (port) {
        case 0:
                at91_ports[idx].membase = (void __iomem *) AT91_VA_BASE_US0;
                at91_ports[idx].mapbase = AT91_VA_BASE_US0;
                at91_ports[idx].irq     = AT91_ID_US0;
                AT91_CfgPIO_USART0();
                break;
        case 1:
                at91_ports[idx].membase = (void __iomem *) AT91_VA_BASE_US1;
                at91_ports[idx].mapbase = AT91_VA_BASE_US1;
                at91_ports[idx].irq     = AT91_ID_US1;
                AT91_CfgPIO_USART1();
                break;
        case 2:
                at91_ports[idx].membase = (void __iomem *) AT91_VA_BASE_US2;
                at91_ports[idx].mapbase = AT91_VA_BASE_US2;
                at91_ports[idx].irq     = AT91_ID_US2;
                AT91_CfgPIO_USART2();
                break;
        case 3:
                at91_ports[idx].membase = (void __iomem *) AT91_VA_BASE_US3;
                at91_ports[idx].mapbase = AT91_VA_BASE_US3;
                at91_ports[idx].irq     = AT91_ID_US3;
                AT91_CfgPIO_USART3();
                break;
        case 4:
                at91_ports[idx].membase = (void __iomem *) AT91_VA_BASE_DBGU;
                at91_ports[idx].mapbase = AT91_VA_BASE_DBGU;
                at91_ports[idx].irq     = AT91_ID_SYS;
                AT91_CfgPIO_DBGU();
                break;
        default:
                printk(KERN_ERR  "%s : bad port number %d\n", __FUNCTION__, port);
        }
}

#ifdef CONFIG_SERIAL_AT91_CONSOLE

/*
 * Interrupts are disabled on entering
 */
static void at91_console_write(struct console *co, const char *s, u_int count)
{
        struct uart_port *port = at91_ports + co->index;
        unsigned int status, i, imr;

        /*
         *      First, save IMR and then disable interrupts
         */
        imr = UART_GET_IMR(port);       /* get interrupt mask */
        UART_PUT_IDR(port, AT91_US_RXRDY | AT91_US_TXRDY);

        /*
         *      Now, do each character
         */
        for (i = 0; i < count; i++) {
                do {
                        status = UART_GET_CSR(port);
                } while (!(status & AT91_US_TXRDY));
                UART_PUT_CHAR(port, s[i]);
                if (s[i] == '\n') {
                        do {
                                status = UART_GET_CSR(port);
                        } while (!(status & AT91_US_TXRDY));
                        UART_PUT_CHAR(port, '\r');
                }
        }

        /*
         *      Finally, wait for transmitter to become empty
         *      and restore IMR
         */
        do {
                status = UART_GET_CSR(port);
        } while (!(status & AT91_US_TXRDY));
        UART_PUT_IER(port, imr);        /* set interrupts back the way they were */
}

/*
 * If the port was already initialised (eg, by a boot loader), try to determine
 * the current setup.
 */
static void __init at91_console_get_options(struct uart_port *port, int *baud, int *parity, int *bits)
{
        unsigned int mr, quot;

// TODO: CR is a write-only register
//      unsigned int cr;
//
//      cr = UART_GET_CR(port) & (AT91_US_RXEN | AT91_US_TXEN);
//      if (cr == (AT91_US_RXEN | AT91_US_TXEN)) {
//              /* ok, the port was enabled */
//      }

        mr = UART_GET_MR(port) & AT91_US_CHRL;
        if (mr == AT91_US_CHRL_8)
                *bits = 8;
        else
                *bits = 7;

        mr = UART_GET_MR(port) & AT91_US_PAR;
        if (mr == AT91_US_PAR_EVEN)
                *parity = 'e';
        else if (mr == AT91_US_PAR_ODD)
                *parity = 'o';

        quot = UART_GET_BRGR(port);
        *baud = port->uartclk / (16 * (quot));
}

static int __init at91_console_setup(struct console *co, char *options)
{
        struct uart_port *port;
        int baud = 115200;
        int bits = 8;
        int parity = 'n';
        int flow = 'n';

        /*
         * Check whether an invalid uart number has been specified, and
         * if so, search for the first available port that does have
         * console support.
         */
        port = uart_get_console(at91_ports, AT91_NR_UART, co);

        /*
         * Enable the serial console, in-case bootloader did not do it.
         */
        at91_sys_write(AT91_PMC_PCER, 1 << port->irq);  /* enable clock */
        UART_PUT_IDR(port, -1);                         /* disable interrupts */
        UART_PUT_CR(port, AT91_US_RSTSTA | AT91_US_RSTRX);
        UART_PUT_CR(port, AT91_US_TXEN | AT91_US_RXEN);

        if (options)
                uart_parse_options(options, &baud, &parity, &bits, &flow);
        else
                at91_console_get_options(port, &baud, &parity, &bits);

        return uart_set_options(port, co, baud, parity, bits, flow);
}

static struct uart_driver at91_uart;

static struct console at91_console = {
        .name           = AT91_DEVICENAME,
        .write          = at91_console_write,
        .device         = uart_console_device,
        .setup          = at91_console_setup,
        .flags          = CON_PRINTBUFFER,
        .index          = -1,
        .data           = &at91_uart,
};

#define AT91_CONSOLE_DEVICE     &at91_console

static int  __init at91_console_init(void)
{
        at91_init_ports();

        at91_console.index = at91_console_port;
        register_console(&at91_console);
        return 0;
}
console_initcall(at91_console_init);

#else
#define AT91_CONSOLE_DEVICE     NULL
#endif

static struct uart_driver at91_uart = {
        .owner                  = THIS_MODULE,
        .driver_name            = AT91_DEVICENAME,
        .dev_name               = AT91_DEVICENAME,
        .devfs_name             = AT91_DEVICENAME,
        .major                  = SERIAL_AT91_MAJOR,
        .minor                  = MINOR_START,
        .nr                     = AT91_NR_UART,
        .cons                   = AT91_CONSOLE_DEVICE,
};

static int __init at91_serial_init(void)
{
        int ret, i;

        at91_init_ports();

        ret = uart_register_driver(&at91_uart);
        if (ret)
                return ret;

        for (i = 0; i < AT91_NR_UART; i++) {
                if (at91_serial_map[i] >= 0)
                        uart_add_one_port(&at91_uart, &at91_ports[i]);
        }

        return 0;
}

static void __exit at91_serial_exit(void)
{
        int i;

        for (i = 0; i < AT91_NR_UART; i++) {
                if (at91_serial_map[i] >= 0)
                        uart_remove_one_port(&at91_uart, &at91_ports[i]);
        }

        uart_unregister_driver(&at91_uart);
}

module_init(at91_serial_init);
module_exit(at91_serial_exit);

MODULE_AUTHOR("Rick Bronson");
MODULE_DESCRIPTION("AT91 generic serial port driver");
MODULE_LICENSE("GPL");