Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

[cris-mirror.git] / drivers / tty / serial / etraxfs-uart.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/module.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/platform_device.h>
#include <linux/serial_core.h>
#include <linux/tty_flip.h>
#include <linux/of.h>
#include <linux/gpio.h>
#include <linux/of_irq.h>
#include <linux/of_address.h>
#include <hwregs/ser_defs.h>

#include "serial_mctrl_gpio.h"

#define DRV_NAME "etraxfs-uart"
#define UART_NR CONFIG_ETRAX_SERIAL_PORTS

#define MODIFY_REG(instance, reg, var)                          \
        do {                                                    \
                if (REG_RD_INT(ser, instance, reg) !=           \
                    REG_TYPE_CONV(int, reg_ser_##reg, var))     \
                        REG_WR(ser, instance, reg, var);        \
        } while (0)

struct uart_cris_port {
        struct uart_port port;

        int initialized;
        int irq;

        void __iomem *regi_ser;

        struct mctrl_gpios *gpios;

        int write_ongoing;
};

static struct uart_driver etraxfs_uart_driver;
static struct uart_port *console_port;
static int console_baud = 115200;
static struct uart_cris_port *etraxfs_uart_ports[UART_NR];

static void cris_serial_port_init(struct uart_port *port, int line);
static void etraxfs_uart_stop_rx(struct uart_port *port);
static inline void etraxfs_uart_start_tx_bottom(struct uart_port *port);

#ifdef CONFIG_SERIAL_ETRAXFS_CONSOLE
static void
cris_console_write(struct console *co, const char *s, unsigned int count)
{
        struct uart_cris_port *up;
        int i;
        reg_ser_r_stat_din stat;
        reg_ser_rw_tr_dma_en tr_dma_en, old;

        up = etraxfs_uart_ports[co->index];

        if (!up)
                return;

        /* Switch to manual mode. */
        tr_dma_en = old = REG_RD(ser, up->regi_ser, rw_tr_dma_en);
        if (tr_dma_en.en == regk_ser_yes) {
                tr_dma_en.en = regk_ser_no;
                REG_WR(ser, up->regi_ser, rw_tr_dma_en, tr_dma_en);
        }

        /* Send data. */
        for (i = 0; i < count; i++) {
                /* LF -> CRLF */
                if (s[i] == '\n') {
                        do {
                                stat = REG_RD(ser, up->regi_ser, r_stat_din);
                        } while (!stat.tr_rdy);
                        REG_WR_INT(ser, up->regi_ser, rw_dout, '\r');
                }
                /* Wait until transmitter is ready and send. */
                do {
                        stat = REG_RD(ser, up->regi_ser, r_stat_din);
                } while (!stat.tr_rdy);
                REG_WR_INT(ser, up->regi_ser, rw_dout, s[i]);
        }

        /* Restore mode. */
        if (tr_dma_en.en != old.en)
                REG_WR(ser, up->regi_ser, rw_tr_dma_en, old);
}

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

        if (co->index < 0 || co->index >= UART_NR)
                co->index = 0;
        port = &etraxfs_uart_ports[co->index]->port;
        console_port = port;

        co->flags |= CON_CONSDEV;

        if (options)
                uart_parse_options(options, &baud, &parity, &bits, &flow);
        console_baud = baud;
        cris_serial_port_init(port, co->index);
        uart_set_options(port, co, baud, parity, bits, flow);

        return 0;
}

static struct console cris_console = {
        .name = "ttyS",
        .write = cris_console_write,
        .device = uart_console_device,
        .setup = cris_console_setup,
        .flags = CON_PRINTBUFFER,
        .index = -1,
        .data = &etraxfs_uart_driver,
};
#endif /* CONFIG_SERIAL_ETRAXFS_CONSOLE */

static struct uart_driver etraxfs_uart_driver = {
        .owner = THIS_MODULE,
        .driver_name = "serial",
        .dev_name = "ttyS",
        .major = TTY_MAJOR,
        .minor = 64,
        .nr = UART_NR,
#ifdef CONFIG_SERIAL_ETRAXFS_CONSOLE
        .cons = &cris_console,
#endif /* CONFIG_SERIAL_ETRAXFS_CONSOLE */
};

static inline int crisv32_serial_get_rts(struct uart_cris_port *up)
{
        void __iomem *regi_ser = up->regi_ser;
        /*
         * Return what the user has controlled rts to or
         * what the pin is? (if auto_rts is used it differs during tx)
         */
        reg_ser_r_stat_din rstat = REG_RD(ser, regi_ser, r_stat_din);

        return !(rstat.rts_n == regk_ser_active);
}

/*
 * A set = 0 means 3.3V on the pin, bitvalue: 0=active, 1=inactive
 *                                            0=0V    , 1=3.3V
 */
static inline void crisv32_serial_set_rts(struct uart_cris_port *up,
                                          int set, int force)
{
        void __iomem *regi_ser = up->regi_ser;

        unsigned long flags;
        reg_ser_rw_rec_ctrl rec_ctrl;

        local_irq_save(flags);
        rec_ctrl = REG_RD(ser, regi_ser, rw_rec_ctrl);

        if (set)
                rec_ctrl.rts_n = regk_ser_active;
        else
                rec_ctrl.rts_n = regk_ser_inactive;
        REG_WR(ser, regi_ser, rw_rec_ctrl, rec_ctrl);
        local_irq_restore(flags);
}

static inline int crisv32_serial_get_cts(struct uart_cris_port *up)
{
        void __iomem *regi_ser = up->regi_ser;
        reg_ser_r_stat_din rstat = REG_RD(ser, regi_ser, r_stat_din);

        return (rstat.cts_n == regk_ser_active);
}

/*
 * Send a single character for XON/XOFF purposes.  We do it in this separate
 * function instead of the alternative support port.x_char, in the ...start_tx
 * function, so we don't mix up this case with possibly enabling transmission
 * of queued-up data (in case that's disabled after *receiving* an XOFF or
 * negative CTS).  This function is used for both DMA and non-DMA case; see HW
 * docs specifically blessing sending characters manually when DMA for
 * transmission is enabled and running.  We may be asked to transmit despite
 * the transmitter being disabled by a ..._stop_tx call so we need to enable
 * it temporarily but restore the state afterwards.
 */
static void etraxfs_uart_send_xchar(struct uart_port *port, char ch)
{
        struct uart_cris_port *up = (struct uart_cris_port *)port;
        reg_ser_rw_dout dout = { .data = ch };
        reg_ser_rw_ack_intr ack_intr = { .tr_rdy = regk_ser_yes };
        reg_ser_r_stat_din rstat;
        reg_ser_rw_tr_ctrl prev_tr_ctrl, tr_ctrl;
        void __iomem *regi_ser = up->regi_ser;
        unsigned long flags;

        /*
         * Wait for tr_rdy in case a character is already being output.  Make
         * sure we have integrity between the register reads and the writes
         * below, but don't busy-wait with interrupts off and the port lock
         * taken.
         */
        spin_lock_irqsave(&port->lock, flags);
        do {
                spin_unlock_irqrestore(&port->lock, flags);
                spin_lock_irqsave(&port->lock, flags);
                prev_tr_ctrl = tr_ctrl = REG_RD(ser, regi_ser, rw_tr_ctrl);
                rstat = REG_RD(ser, regi_ser, r_stat_din);
        } while (!rstat.tr_rdy);

        /*
         * Ack an interrupt if one was just issued for the previous character
         * that was output.  This is required for non-DMA as the interrupt is
         * used as the only indicator that the transmitter is ready and it
         * isn't while this x_char is being transmitted.
         */
        REG_WR(ser, regi_ser, rw_ack_intr, ack_intr);

        /* Enable the transmitter in case it was disabled. */
        tr_ctrl.stop = 0;
        REG_WR(ser, regi_ser, rw_tr_ctrl, tr_ctrl);

        /*
         * Finally, send the blessed character; nothing should stop it now,
         * except for an xoff-detected state, which we'll handle below.
         */
        REG_WR(ser, regi_ser, rw_dout, dout);
        up->port.icount.tx++;

        /* There might be an xoff state to clear. */
        rstat = REG_RD(ser, up->regi_ser, r_stat_din);

        /*
         * Clear any xoff state that *may* have been there to
         * inhibit transmission of the character.
         */
        if (rstat.xoff_detect) {
                reg_ser_rw_xoff_clr xoff_clr = { .clr = 1 };
                reg_ser_rw_tr_dma_en tr_dma_en;

                REG_WR(ser, regi_ser, rw_xoff_clr, xoff_clr);
                tr_dma_en = REG_RD(ser, regi_ser, rw_tr_dma_en);

                /*
                 * If we had an xoff state but cleared it, instead sneak in a
                 * disabled state for the transmitter, after the character we
                 * sent.  Thus we keep the port disabled, just as if the xoff
                 * state was still in effect (or actually, as if stop_tx had
                 * been called, as we stop DMA too).
                 */
                prev_tr_ctrl.stop = 1;

                tr_dma_en.en = 0;
                REG_WR(ser, regi_ser, rw_tr_dma_en, tr_dma_en);
        }

        /* Restore "previous" enabled/disabled state of the transmitter. */
        REG_WR(ser, regi_ser, rw_tr_ctrl, prev_tr_ctrl);

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

/*
 * Do not spin_lock_irqsave or disable interrupts by other means here; it's
 * already done by the caller.
 */
static void etraxfs_uart_start_tx(struct uart_port *port)
{
        struct uart_cris_port *up = (struct uart_cris_port *)port;

        /* we have already done below if a write is ongoing */
        if (up->write_ongoing)
                return;

        /* Signal that write is ongoing */
        up->write_ongoing = 1;

        etraxfs_uart_start_tx_bottom(port);
}

static inline void etraxfs_uart_start_tx_bottom(struct uart_port *port)
{
        struct uart_cris_port *up = (struct uart_cris_port *)port;
        void __iomem *regi_ser = up->regi_ser;
        reg_ser_rw_tr_ctrl tr_ctrl;
        reg_ser_rw_intr_mask intr_mask;

        tr_ctrl = REG_RD(ser, regi_ser, rw_tr_ctrl);
        tr_ctrl.stop = regk_ser_no;
        REG_WR(ser, regi_ser, rw_tr_ctrl, tr_ctrl);
        intr_mask = REG_RD(ser, regi_ser, rw_intr_mask);
        intr_mask.tr_rdy = regk_ser_yes;
        REG_WR(ser, regi_ser, rw_intr_mask, intr_mask);
}

/*
 * This function handles both the DMA and non-DMA case by ordering the
 * transmitter to stop of after the current character.  We don't need to wait
 * for any such character to be completely transmitted; we do that where it
 * matters, like in etraxfs_uart_set_termios.  Don't busy-wait here; see
 * Documentation/serial/driver: this function is called within
 * spin_lock_irq{,save} and thus separate ones would be disastrous (when SMP).
 * There's no documented need to set the txd pin to any particular value;
 * break setting is controlled solely by etraxfs_uart_break_ctl.
 */
static void etraxfs_uart_stop_tx(struct uart_port *port)
{
        struct uart_cris_port *up = (struct uart_cris_port *)port;
        void __iomem *regi_ser = up->regi_ser;
        reg_ser_rw_tr_ctrl tr_ctrl;
        reg_ser_rw_intr_mask intr_mask;
        reg_ser_rw_tr_dma_en tr_dma_en = {0};
        reg_ser_rw_xoff_clr xoff_clr = {0};

        /*
         * For the non-DMA case, we'd get a tr_rdy interrupt that we're not
         * interested in as we're not transmitting any characters.  For the
         * DMA case, that interrupt is already turned off, but no reason to
         * waste code on conditionals here.
         */
        intr_mask = REG_RD(ser, regi_ser, rw_intr_mask);
        intr_mask.tr_rdy = regk_ser_no;
        REG_WR(ser, regi_ser, rw_intr_mask, intr_mask);

        tr_ctrl = REG_RD(ser, regi_ser, rw_tr_ctrl);
        tr_ctrl.stop = 1;
        REG_WR(ser, regi_ser, rw_tr_ctrl, tr_ctrl);

        /*
         * Always clear possible hardware xoff-detected state here, no need to
         * unnecessary consider mctrl settings and when they change.  We clear
         * it here rather than in start_tx: both functions are called as the
         * effect of XOFF processing, but start_tx is also called when upper
         * levels tell the driver that there are more characters to send, so
         * avoid adding code there.
         */
        xoff_clr.clr = 1;
        REG_WR(ser, regi_ser, rw_xoff_clr, xoff_clr);

        /*
         * Disable transmitter DMA, so that if we're in XON/XOFF, we can send
         * those single characters without also giving go-ahead for queued up
         * DMA data.
         */
        tr_dma_en.en = 0;
        REG_WR(ser, regi_ser, rw_tr_dma_en, tr_dma_en);

        /*
         * Make sure that write_ongoing is reset when stopping tx.
         */
        up->write_ongoing = 0;
}

static void etraxfs_uart_stop_rx(struct uart_port *port)
{
        struct uart_cris_port *up = (struct uart_cris_port *)port;
        void __iomem *regi_ser = up->regi_ser;
        reg_ser_rw_rec_ctrl rec_ctrl = REG_RD(ser, regi_ser, rw_rec_ctrl);

        rec_ctrl.en = regk_ser_no;
        REG_WR(ser, regi_ser, rw_rec_ctrl, rec_ctrl);
}

static unsigned int etraxfs_uart_tx_empty(struct uart_port *port)
{
        struct uart_cris_port *up = (struct uart_cris_port *)port;
        unsigned long flags;
        unsigned int ret;
        reg_ser_r_stat_din rstat = {0};

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

        rstat = REG_RD(ser, up->regi_ser, r_stat_din);
        ret = rstat.tr_empty ? TIOCSER_TEMT : 0;

        spin_unlock_irqrestore(&up->port.lock, flags);
        return ret;
}
static unsigned int etraxfs_uart_get_mctrl(struct uart_port *port)
{
        struct uart_cris_port *up = (struct uart_cris_port *)port;
        unsigned int ret;

        ret = 0;
        if (crisv32_serial_get_rts(up))
                ret |= TIOCM_RTS;
        if (crisv32_serial_get_cts(up))
                ret |= TIOCM_CTS;
        return mctrl_gpio_get(up->gpios, &ret);
}

static void etraxfs_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
        struct uart_cris_port *up = (struct uart_cris_port *)port;

        crisv32_serial_set_rts(up, mctrl & TIOCM_RTS ? 1 : 0, 0);
        mctrl_gpio_set(up->gpios, mctrl);
}

static void etraxfs_uart_break_ctl(struct uart_port *port, int break_state)
{
        struct uart_cris_port *up = (struct uart_cris_port *)port;
        unsigned long flags;
        reg_ser_rw_tr_ctrl tr_ctrl;
        reg_ser_rw_tr_dma_en tr_dma_en;
        reg_ser_rw_intr_mask intr_mask;

        spin_lock_irqsave(&up->port.lock, flags);
        tr_ctrl = REG_RD(ser, up->regi_ser, rw_tr_ctrl);
        tr_dma_en = REG_RD(ser, up->regi_ser, rw_tr_dma_en);
        intr_mask = REG_RD(ser, up->regi_ser, rw_intr_mask);

        if (break_state != 0) { /* Send break */
                /*
                 * We need to disable DMA (if used) or tr_rdy interrupts if no
                 * DMA.  No need to make this conditional on use of DMA;
                 * disabling will be a no-op for the other mode.
                 */
                intr_mask.tr_rdy = regk_ser_no;
                tr_dma_en.en = 0;

                /*
                 * Stop transmission and set the txd pin to 0 after the
                 * current character.  The txd setting will take effect after
                 * any current transmission has completed.
                 */
                tr_ctrl.stop = 1;
                tr_ctrl.txd = 0;
        } else {
                /* Re-enable the serial interrupt. */
                intr_mask.tr_rdy = regk_ser_yes;

                tr_ctrl.stop = 0;
                tr_ctrl.txd = 1;
        }
        REG_WR(ser, up->regi_ser, rw_tr_ctrl, tr_ctrl);
        REG_WR(ser, up->regi_ser, rw_tr_dma_en, tr_dma_en);
        REG_WR(ser, up->regi_ser, rw_intr_mask, intr_mask);

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

static void
transmit_chars_no_dma(struct uart_cris_port *up)
{
        int max_count;
        struct circ_buf *xmit = &up->port.state->xmit;

        void __iomem *regi_ser = up->regi_ser;
        reg_ser_r_stat_din rstat;
        reg_ser_rw_ack_intr ack_intr = { .tr_rdy = regk_ser_yes };

        if (uart_circ_empty(xmit) || uart_tx_stopped(&up->port)) {
                /* No more to send, so disable the interrupt. */
                reg_ser_rw_intr_mask intr_mask;

                intr_mask = REG_RD(ser, regi_ser, rw_intr_mask);
                intr_mask.tr_rdy = 0;
                intr_mask.tr_empty = 0;
                REG_WR(ser, regi_ser, rw_intr_mask, intr_mask);
                up->write_ongoing = 0;
                return;
        }

        /* If the serport is fast, we send up to max_count bytes before
           exiting the loop.  */
        max_count = 64;
        do {
                reg_ser_rw_dout dout = { .data = xmit->buf[xmit->tail] };

                REG_WR(ser, regi_ser, rw_dout, dout);
                REG_WR(ser, regi_ser, rw_ack_intr, ack_intr);
                xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE-1);
                up->port.icount.tx++;
                if (xmit->head == xmit->tail)
                        break;
                rstat = REG_RD(ser, regi_ser, r_stat_din);
        } while ((--max_count > 0) && rstat.tr_rdy);

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

static void receive_chars_no_dma(struct uart_cris_port *up)
{
        reg_ser_rs_stat_din stat_din;
        reg_ser_r_stat_din rstat;
        struct tty_port *port;
        struct uart_icount *icount;
        int max_count = 16;
        char flag;
        reg_ser_rw_ack_intr ack_intr = { 0 };

        rstat = REG_RD(ser, up->regi_ser, r_stat_din);
        icount = &up->port.icount;
        port = &up->port.state->port;

        do {
                stat_din = REG_RD(ser, up->regi_ser, rs_stat_din);

                flag = TTY_NORMAL;
                ack_intr.dav = 1;
                REG_WR(ser, up->regi_ser, rw_ack_intr, ack_intr);
                icount->rx++;

                if (stat_din.framing_err | stat_din.par_err | stat_din.orun) {
                        if (stat_din.data == 0x00 &&
                            stat_din.framing_err) {
                                /* Most likely a break. */
                                flag = TTY_BREAK;
                                icount->brk++;
                        } else if (stat_din.par_err) {
                                flag = TTY_PARITY;
                                icount->parity++;
                        } else if (stat_din.orun) {
                                flag = TTY_OVERRUN;
                                icount->overrun++;
                        } else if (stat_din.framing_err) {
                                flag = TTY_FRAME;
                                icount->frame++;
                        }
                }

                /*
                 * If this becomes important, we probably *could* handle this
                 * gracefully by keeping track of the unhandled character.
                 */
                if (!tty_insert_flip_char(port, stat_din.data, flag))
                        panic("%s: No tty buffer space", __func__);
                rstat = REG_RD(ser, up->regi_ser, r_stat_din);
        } while (rstat.dav && (max_count-- > 0));
        spin_unlock(&up->port.lock);
        tty_flip_buffer_push(port);
        spin_lock(&up->port.lock);
}

static irqreturn_t
ser_interrupt(int irq, void *dev_id)
{
        struct uart_cris_port *up = (struct uart_cris_port *)dev_id;
        void __iomem *regi_ser;
        int handled = 0;

        spin_lock(&up->port.lock);

        regi_ser = up->regi_ser;

        if (regi_ser) {
                reg_ser_r_masked_intr masked_intr;

                masked_intr = REG_RD(ser, regi_ser, r_masked_intr);
                /*
                 * Check what interrupts are active before taking
                 * actions. If DMA is used the interrupt shouldn't
                 * be enabled.
                 */
                if (masked_intr.dav) {
                        receive_chars_no_dma(up);
                        handled = 1;
                }

                if (masked_intr.tr_rdy) {
                        transmit_chars_no_dma(up);
                        handled = 1;
                }
        }
        spin_unlock(&up->port.lock);
        return IRQ_RETVAL(handled);
}

#ifdef CONFIG_CONSOLE_POLL
static int etraxfs_uart_get_poll_char(struct uart_port *port)
{
        reg_ser_rs_stat_din stat;
        reg_ser_rw_ack_intr ack_intr = { 0 };
        struct uart_cris_port *up = (struct uart_cris_port *)port;

        do {
                stat = REG_RD(ser, up->regi_ser, rs_stat_din);
        } while (!stat.dav);

        /* Ack the data_avail interrupt. */
        ack_intr.dav = 1;
        REG_WR(ser, up->regi_ser, rw_ack_intr, ack_intr);

        return stat.data;
}

static void etraxfs_uart_put_poll_char(struct uart_port *port,
                                        unsigned char c)
{
        reg_ser_r_stat_din stat;
        struct uart_cris_port *up = (struct uart_cris_port *)port;

        do {
                stat = REG_RD(ser, up->regi_ser, r_stat_din);
        } while (!stat.tr_rdy);
        REG_WR_INT(ser, up->regi_ser, rw_dout, c);
}
#endif /* CONFIG_CONSOLE_POLL */

static int etraxfs_uart_startup(struct uart_port *port)
{
        struct uart_cris_port *up = (struct uart_cris_port *)port;
        unsigned long flags;
        reg_ser_rw_intr_mask ser_intr_mask = {0};

        ser_intr_mask.dav = regk_ser_yes;

        if (request_irq(etraxfs_uart_ports[port->line]->irq, ser_interrupt,
                        0, DRV_NAME, etraxfs_uart_ports[port->line]))
                panic("irq ser%d", port->line);

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

        REG_WR(ser, up->regi_ser, rw_intr_mask, ser_intr_mask);

        etraxfs_uart_set_mctrl(&up->port, up->port.mctrl);

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

        return 0;
}

static void etraxfs_uart_shutdown(struct uart_port *port)
{
        struct uart_cris_port *up = (struct uart_cris_port *)port;
        unsigned long flags;

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

        etraxfs_uart_stop_tx(port);
        etraxfs_uart_stop_rx(port);

        free_irq(etraxfs_uart_ports[port->line]->irq,
                 etraxfs_uart_ports[port->line]);

        etraxfs_uart_set_mctrl(&up->port, up->port.mctrl);

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

}

static void
etraxfs_uart_set_termios(struct uart_port *port, struct ktermios *termios,
                         struct ktermios *old)
{
        struct uart_cris_port *up = (struct uart_cris_port *)port;
        unsigned long flags;
        reg_ser_rw_xoff xoff;
        reg_ser_rw_xoff_clr xoff_clr = {0};
        reg_ser_rw_tr_ctrl tx_ctrl = {0};
        reg_ser_rw_tr_dma_en tx_dma_en = {0};
        reg_ser_rw_rec_ctrl rx_ctrl = {0};
        reg_ser_rw_tr_baud_div tx_baud_div = {0};
        reg_ser_rw_rec_baud_div rx_baud_div = {0};
        int baud;

        if (old &&
            termios->c_cflag == old->c_cflag &&
            termios->c_iflag == old->c_iflag)
                return;

        /* Tx: 8 bit, no/even parity, 1 stop bit, no cts. */
        tx_ctrl.base_freq = regk_ser_f29_493;
        tx_ctrl.en = 0;
        tx_ctrl.stop = 0;
        tx_ctrl.auto_rts = regk_ser_no;
        tx_ctrl.txd = 1;
        tx_ctrl.auto_cts = 0;
        /* Rx: 8 bit, no/even parity. */
        rx_ctrl.dma_err = regk_ser_stop;
        rx_ctrl.sampling = regk_ser_majority;
        rx_ctrl.timeout = 1;

        rx_ctrl.rts_n = regk_ser_inactive;

        /* Common for tx and rx: 8N1. */
        tx_ctrl.data_bits = regk_ser_bits8;
        rx_ctrl.data_bits = regk_ser_bits8;
        tx_ctrl.par = regk_ser_even;
        rx_ctrl.par = regk_ser_even;
        tx_ctrl.par_en = regk_ser_no;
        rx_ctrl.par_en = regk_ser_no;

        tx_ctrl.stop_bits = regk_ser_bits1;

        /*
         * Change baud-rate and write it to the hardware.
         *
         * baud_clock = base_freq / (divisor*8)
         * divisor = base_freq / (baud_clock * 8)
         * base_freq is either:
         * off, ext, 29.493MHz, 32.000 MHz, 32.768 MHz or 100 MHz
         * 20.493MHz is used for standard baudrates
         */

        /*
         * For the console port we keep the original baudrate here.  Not very
         * beautiful.
         */
        if ((port != console_port) || old)
                baud = uart_get_baud_rate(port, termios, old, 0,
                                          port->uartclk / 8);
        else
                baud = console_baud;

        tx_baud_div.div = 29493000 / (8 * baud);
        /* Rx uses same as tx. */
        rx_baud_div.div = tx_baud_div.div;
        rx_ctrl.base_freq = tx_ctrl.base_freq;

        if ((termios->c_cflag & CSIZE) == CS7) {
                /* Set 7 bit mode. */
                tx_ctrl.data_bits = regk_ser_bits7;
                rx_ctrl.data_bits = regk_ser_bits7;
        }

        if (termios->c_cflag & CSTOPB) {
                /* Set 2 stop bit mode. */
                tx_ctrl.stop_bits = regk_ser_bits2;
        }

        if (termios->c_cflag & PARENB) {
                /* Enable parity. */
                tx_ctrl.par_en = regk_ser_yes;
                rx_ctrl.par_en = regk_ser_yes;
        }

        if (termios->c_cflag & CMSPAR) {
                if (termios->c_cflag & PARODD) {
                        /* Set mark parity if PARODD and CMSPAR. */
                        tx_ctrl.par = regk_ser_mark;
                        rx_ctrl.par = regk_ser_mark;
                } else {
                        tx_ctrl.par = regk_ser_space;
                        rx_ctrl.par = regk_ser_space;
                }
        } else {
                if (termios->c_cflag & PARODD) {
                        /* Set odd parity. */
                       tx_ctrl.par = regk_ser_odd;
                       rx_ctrl.par = regk_ser_odd;
                }
        }

        if (termios->c_cflag & CRTSCTS) {
                /* Enable automatic CTS handling. */
                tx_ctrl.auto_cts = regk_ser_yes;
        }

        /* Make sure the tx and rx are enabled. */
        tx_ctrl.en = regk_ser_yes;
        rx_ctrl.en = regk_ser_yes;

        spin_lock_irqsave(&port->lock, flags);

        tx_dma_en.en = 0;
        REG_WR(ser, up->regi_ser, rw_tr_dma_en, tx_dma_en);

        /* Actually write the control regs (if modified) to the hardware. */
        uart_update_timeout(port, termios->c_cflag, port->uartclk/8);
        MODIFY_REG(up->regi_ser, rw_rec_baud_div, rx_baud_div);
        MODIFY_REG(up->regi_ser, rw_rec_ctrl, rx_ctrl);

        MODIFY_REG(up->regi_ser, rw_tr_baud_div, tx_baud_div);
        MODIFY_REG(up->regi_ser, rw_tr_ctrl, tx_ctrl);

        tx_dma_en.en = 0;
        REG_WR(ser, up->regi_ser, rw_tr_dma_en, tx_dma_en);

        xoff = REG_RD(ser, up->regi_ser, rw_xoff);

        if (up->port.state && up->port.state->port.tty &&
            (up->port.state->port.tty->termios.c_iflag & IXON)) {
                xoff.chr = STOP_CHAR(up->port.state->port.tty);
                xoff.automatic = regk_ser_yes;
        } else
                xoff.automatic = regk_ser_no;

        MODIFY_REG(up->regi_ser, rw_xoff, xoff);

        /*
         * Make sure we don't start in an automatically shut-off state due to
         * a previous early exit.
         */
        xoff_clr.clr = 1;
        REG_WR(ser, up->regi_ser, rw_xoff_clr, xoff_clr);

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

static const char *
etraxfs_uart_type(struct uart_port *port)
{
        return "CRISv32";
}

static void etraxfs_uart_release_port(struct uart_port *port)
{
}

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

static void etraxfs_uart_config_port(struct uart_port *port, int flags)
{
        struct uart_cris_port *up = (struct uart_cris_port *)port;

        up->port.type = PORT_CRIS;
}

static const struct uart_ops etraxfs_uart_pops = {
        .tx_empty = etraxfs_uart_tx_empty,
        .set_mctrl = etraxfs_uart_set_mctrl,
        .get_mctrl = etraxfs_uart_get_mctrl,
        .stop_tx = etraxfs_uart_stop_tx,
        .start_tx = etraxfs_uart_start_tx,
        .send_xchar = etraxfs_uart_send_xchar,
        .stop_rx = etraxfs_uart_stop_rx,
        .break_ctl = etraxfs_uart_break_ctl,
        .startup = etraxfs_uart_startup,
        .shutdown = etraxfs_uart_shutdown,
        .set_termios = etraxfs_uart_set_termios,
        .type = etraxfs_uart_type,
        .release_port = etraxfs_uart_release_port,
        .request_port = etraxfs_uart_request_port,
        .config_port = etraxfs_uart_config_port,
#ifdef CONFIG_CONSOLE_POLL
        .poll_get_char = etraxfs_uart_get_poll_char,
        .poll_put_char = etraxfs_uart_put_poll_char,
#endif
};

static void cris_serial_port_init(struct uart_port *port, int line)
{
        struct uart_cris_port *up = (struct uart_cris_port *)port;

        if (up->initialized)
                return;
        up->initialized = 1;
        port->line = line;
        spin_lock_init(&port->lock);
        port->ops = &etraxfs_uart_pops;
        port->irq = up->irq;
        port->iobase = (unsigned long) up->regi_ser;
        port->uartclk = 29493000;

        /*
         * We can't fit any more than 255 here (unsigned char), though
         * actually UART_XMIT_SIZE characters could be pending output.
         * At time of this writing, the definition of "fifosize" is here the
         * amount of characters that can be pending output after a start_tx call
         * until tx_empty returns 1: see serial_core.c:uart_wait_until_sent.
         * This matters for timeout calculations unfortunately, but keeping
         * larger amounts at the DMA wouldn't win much so let's just play nice.
         */
        port->fifosize = 255;
        port->flags = UPF_BOOT_AUTOCONF;
}

static int etraxfs_uart_probe(struct platform_device *pdev)
{
        struct device_node *np = pdev->dev.of_node;
        struct uart_cris_port *up;
        int dev_id;

        if (!np)
                return -ENODEV;

        dev_id = of_alias_get_id(np, "serial");
        if (dev_id < 0)
                dev_id = 0;

        if (dev_id >= UART_NR)
                return -EINVAL;

        if (etraxfs_uart_ports[dev_id])
                return -EBUSY;

        up = devm_kzalloc(&pdev->dev, sizeof(struct uart_cris_port),
                          GFP_KERNEL);
        if (!up)
                return -ENOMEM;

        up->irq = irq_of_parse_and_map(np, 0);
        up->regi_ser = of_iomap(np, 0);
        up->port.dev = &pdev->dev;

        up->gpios = mctrl_gpio_init_noauto(&pdev->dev, 0);
        if (IS_ERR(up->gpios))
                return PTR_ERR(up->gpios);

        cris_serial_port_init(&up->port, dev_id);

        etraxfs_uart_ports[dev_id] = up;
        platform_set_drvdata(pdev, &up->port);
        uart_add_one_port(&etraxfs_uart_driver, &up->port);

        return 0;
}

static int etraxfs_uart_remove(struct platform_device *pdev)
{
        struct uart_port *port;

        port = platform_get_drvdata(pdev);
        uart_remove_one_port(&etraxfs_uart_driver, port);
        etraxfs_uart_ports[port->line] = NULL;

        return 0;
}

static const struct of_device_id etraxfs_uart_dt_ids[] = {
        { .compatible = "axis,etraxfs-uart" },
        { /* sentinel */ }
};

MODULE_DEVICE_TABLE(of, etraxfs_uart_dt_ids);

static struct platform_driver etraxfs_uart_platform_driver = {
        .driver = {
                .name   = DRV_NAME,
                .of_match_table = of_match_ptr(etraxfs_uart_dt_ids),
        },
        .probe          = etraxfs_uart_probe,
        .remove         = etraxfs_uart_remove,
};

static int __init etraxfs_uart_init(void)
{
        int ret;

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

        ret = platform_driver_register(&etraxfs_uart_platform_driver);
        if (ret)
                uart_unregister_driver(&etraxfs_uart_driver);

        return ret;
}

static void __exit etraxfs_uart_exit(void)
{
        platform_driver_unregister(&etraxfs_uart_platform_driver);
        uart_unregister_driver(&etraxfs_uart_driver);
}

module_init(etraxfs_uart_init);
module_exit(etraxfs_uart_exit);