serial: driver for ETRAX FS UART

This is the last missing piece to get a kernel booting to a prompt in qemu-cris.

Signed-off-by: Niklas Cassel <nks@flawful.org>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 996 insertions, 0 deletions

diff --git a/drivers/tty/serial/etraxfs-uart.c b/drivers/tty/serial/etraxfs-uart.c
new file mode 100644
index 000000000000..a57301a6fe42
--- /dev/null
+++ b/drivers/tty/serial/etraxfs-uart.c
@@ -0,0 +1,996 @@
+#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>
+
+#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 gpio_desc *dtr_pin;
+	struct gpio_desc *dsr_pin;
+	struct gpio_desc *ri_pin;
+	struct gpio_desc *cd_pin;
+
+	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 tty_driver *cris_console_device(struct console *co, int *index)
+{
+	struct uart_driver *p = co->data;
+	*index = co->index;
+	return p->tty_driver;
+}
+
+static struct console cris_console = {
+	.name = "ttyS",
+	.write = cris_console_write,
+	.device = cris_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 void etraxfs_uart_enable_ms(struct uart_port *port)
+{
+}
+
+static void check_modem_status(struct uart_cris_port *up)
+{
+}
+
+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;
+	/* DTR is active low */
+	if (up->dtr_pin && !gpiod_get_raw_value(up->dtr_pin))
+		ret |= TIOCM_DTR;
+	/* CD is active low */
+	if (up->cd_pin && !gpiod_get_raw_value(up->cd_pin))
+		ret |= TIOCM_CD;
+	/* RI is active low */
+	if (up->ri_pin && !gpiod_get_raw_value(up->ri_pin))
+		ret |= TIOCM_RI;
+	/* DSR is active low */
+	if (up->dsr_pin && !gpiod_get_raw_value(up->dsr_pin))
+		ret |= TIOCM_DSR;
+	if (crisv32_serial_get_cts(up))
+		ret |= TIOCM_CTS;
+	return 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);
+	/* DTR is active low */
+	if (up->dtr_pin)
+		gpiod_set_raw_value(up->dtr_pin, mctrl & TIOCM_DTR ? 0 : 1);
+	/* RI is active low */
+	if (up->ri_pin)
+		gpiod_set_raw_value(up->ri_pin, mctrl & TIOCM_RNG ? 0 : 1);
+	/* CD is active low */
+	if (up->cd_pin)
+		gpiod_set_raw_value(up->cd_pin, mctrl & TIOCM_CD ? 0 : 1);
+}
+
+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;
+		}
+		check_modem_status(up);
+
+		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,
+	.enable_ms = etraxfs_uart_enable_ms,
+	.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->dtr_pin = devm_gpiod_get_optional(&pdev->dev, "dtr");
+	up->dsr_pin = devm_gpiod_get_optional(&pdev->dev, "dsr");
+	up->ri_pin = devm_gpiod_get_optional(&pdev->dev, "ri");
+	up->cd_pin = devm_gpiod_get_optional(&pdev->dev, "cd");
+	up->port.dev = &pdev->dev;
+	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[pdev->id] = 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);