zs: move to the serial subsystem

This is a reimplementation of the zs driver for the serial subsystem.  Any
resemblance to the old driver is purely coincidential.  ;-) I do hope I got
the handling of modem lines right -- better do not tackle me about the
issue unless you feel too good...

Any users of the old driver: please note the numbers of the serial lines
have now been swapped, i.e.  ttyS0 <-> ttyS1 and ttyS2 <-> ttyS3.  It has
to do with the modem lines mentioned above; basically the port A in a given
chip has to be initialised before the port B if you want to use the latter
as the serial console (which is usually the case), as operations on modem
lines of the serial line associated with the port B access both ports (see
the comment at the top of the driver for the details of wiring used).
Please update your scripts.

This is also the reason each SCC now requests an IRQ once only (as seen in
"/proc/interrupts") -- the handler takes care of both ports at once as the
line associated with the port B has to take status update interrupts from
both ports (and yet the line of the port A takes its own for itself too).
The old driver never got it right...

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1287 insertions, 0 deletions

diff --git a/drivers/serial/zs.c b/drivers/serial/zs.c
new file mode 100644
index 000000000000..65f1294fd27b
--- /dev/null
+++ b/drivers/serial/zs.c
@@ -0,0 +1,1287 @@
+/*
+ * zs.c: Serial port driver for IOASIC DECstations.
+ *
+ * Derived from drivers/sbus/char/sunserial.c by Paul Mackerras.
+ * Derived from drivers/macintosh/macserial.c by Harald Koerfgen.
+ *
+ * DECstation changes
+ * Copyright (C) 1998-2000 Harald Koerfgen
+ * Copyright (C) 2000, 2001, 2002, 2003, 2004, 2005, 2007  Maciej W. Rozycki
+ *
+ * For the rest of the code the original Copyright applies:
+ * Copyright (C) 1996 Paul Mackerras (Paul.Mackerras@cs.anu.edu.au)
+ * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
+ *
+ *
+ * Note: for IOASIC systems the wiring is as follows:
+ *
+ * mouse/keyboard:
+ * DIN-7 MJ-4  signal        SCC
+ * 2     1     TxD       <-  A.TxD
+ * 3     4     RxD       ->  A.RxD
+ *
+ * EIA-232/EIA-423:
+ * DB-25 MMJ-6 signal        SCC
+ * 2     2     TxD       <-  B.TxD
+ * 3     5     RxD       ->  B.RxD
+ * 4           RTS       <- ~A.RTS
+ * 5           CTS       -> ~B.CTS
+ * 6     6     DSR       -> ~A.SYNC
+ * 8           CD        -> ~B.DCD
+ * 12          DSRS(DCE) -> ~A.CTS  (*)
+ * 15          TxC       ->  B.TxC
+ * 17          RxC       ->  B.RxC
+ * 20    1     DTR       <- ~A.DTR
+ * 22          RI        -> ~A.DCD
+ * 23          DSRS(DTE) <- ~B.RTS
+ *
+ * (*) EIA-232 defines the signal at this pin to be SCD, while DSRS(DCE)
+ *     is shared with DSRS(DTE) at pin 23.
+ *
+ * As you can immediately notice the wiring of the RTS, DTR and DSR signals
+ * is a bit odd.  This makes the handling of port B unnecessarily
+ * complicated and prevents the use of some automatic modes of operation.
+ */
+
+#if defined(CONFIG_SERIAL_ZS_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
+#define SUPPORT_SYSRQ
+#endif
+
+#include <linux/bug.h>
+#include <linux/console.h>
+#include <linux/delay.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/ioport.h>
+#include <linux/irqflags.h>
+#include <linux/kernel.h>
+#include <linux/major.h>
+#include <linux/serial.h>
+#include <linux/serial_core.h>
+#include <linux/spinlock.h>
+#include <linux/sysrq.h>
+#include <linux/tty.h>
+#include <linux/types.h>
+
+#include <asm/atomic.h>
+#include <asm/system.h>
+
+#include <asm/dec/interrupts.h>
+#include <asm/dec/ioasic_addrs.h>
+#include <asm/dec/system.h>
+
+#include "zs.h"
+
+
+MODULE_AUTHOR("Maciej W. Rozycki <macro@linux-mips.org>");
+MODULE_DESCRIPTION("DECstation Z85C30 serial driver");
+MODULE_LICENSE("GPL");
+
+
+static char zs_name[] __initdata = "DECstation Z85C30 serial driver version ";
+static char zs_version[] __initdata = "0.10";
+
+/*
+ * It would be nice to dynamically allocate everything that
+ * depends on ZS_NUM_SCCS, so we could support any number of
+ * Z85C30s, but for now...
+ */
+#define ZS_NUM_SCCS	2		/* Max # of ZS chips supported.  */
+#define ZS_NUM_CHAN	2		/* 2 channels per chip.  */
+#define ZS_CHAN_A	0		/* Index of the channel A.  */
+#define ZS_CHAN_B	1		/* Index of the channel B.  */
+#define ZS_CHAN_IO_SIZE 8		/* IOMEM space size.  */
+#define ZS_CHAN_IO_STRIDE 4		/* Register alignment.  */
+#define ZS_CHAN_IO_OFFSET 1		/* The SCC resides on the high byte
+					   of the 16-bit IOBUS.  */
+#define ZS_CLOCK        7372800 	/* Z85C30 PCLK input clock rate.  */
+
+#define to_zport(uport) container_of(uport, struct zs_port, port)
+
+struct zs_parms {
+	resource_size_t scc[ZS_NUM_SCCS];
+	int irq[ZS_NUM_SCCS];
+};
+
+static struct zs_scc zs_sccs[ZS_NUM_SCCS];
+
+static u8 zs_init_regs[ZS_NUM_REGS] __initdata = {
+	0,				/* write 0 */
+	PAR_SPEC,			/* write 1 */
+	0,				/* write 2 */
+	0,				/* write 3 */
+	X16CLK | SB1,			/* write 4 */
+	0,				/* write 5 */
+	0, 0, 0,			/* write 6, 7, 8 */
+	MIE | DLC | NV,			/* write 9 */
+	NRZ,				/* write 10 */
+	TCBR | RCBR,			/* write 11 */
+	0, 0,				/* BRG time constant, write 12 + 13 */
+	BRSRC | BRENABL,		/* write 14 */
+	0,				/* write 15 */
+};
+
+/*
+ * Debugging.
+ */
+#undef ZS_DEBUG_REGS
+
+
+/*
+ * Reading and writing Z85C30 registers.
+ */
+static void recovery_delay(void)
+{
+	udelay(2);
+}
+
+static u8 read_zsreg(struct zs_port *zport, int reg)
+{
+	void __iomem *control = zport->port.membase + ZS_CHAN_IO_OFFSET;
+	u8 retval;
+
+	if (reg != 0) {
+		writeb(reg & 0xf, control);
+		fast_iob();
+		recovery_delay();
+	}
+	retval = readb(control);
+	recovery_delay();
+	return retval;
+}
+
+static void write_zsreg(struct zs_port *zport, int reg, u8 value)
+{
+	void __iomem *control = zport->port.membase + ZS_CHAN_IO_OFFSET;
+
+	if (reg != 0) {
+		writeb(reg & 0xf, control);
+		fast_iob(); recovery_delay();
+	}
+	writeb(value, control);
+	fast_iob();
+	recovery_delay();
+	return;
+}
+
+static u8 read_zsdata(struct zs_port *zport)
+{
+	void __iomem *data = zport->port.membase +
+			     ZS_CHAN_IO_STRIDE + ZS_CHAN_IO_OFFSET;
+	u8 retval;
+
+	retval = readb(data);
+	recovery_delay();
+	return retval;
+}
+
+static void write_zsdata(struct zs_port *zport, u8 value)
+{
+	void __iomem *data = zport->port.membase +
+			     ZS_CHAN_IO_STRIDE + ZS_CHAN_IO_OFFSET;
+
+	writeb(value, data);
+	fast_iob();
+	recovery_delay();
+	return;
+}
+
+#ifdef ZS_DEBUG_REGS
+void zs_dump(void)
+{
+	struct zs_port *zport;
+	int i, j;
+
+	for (i = 0; i < ZS_NUM_SCCS * ZS_NUM_CHAN; i++) {
+		zport = &zs_sccs[i / ZS_NUM_CHAN].zport[i % ZS_NUM_CHAN];
+
+		if (!zport->scc)
+			continue;
+
+		for (j = 0; j < 16; j++)
+			printk("W%-2d = 0x%02x\t", j, zport->regs[j]);
+		printk("\n");
+		for (j = 0; j < 16; j++)
+			printk("R%-2d = 0x%02x\t", j, read_zsreg(zport, j));
+		printk("\n\n");
+	}
+}
+#endif
+
+
+static void zs_spin_lock_cond_irq(spinlock_t *lock, int irq)
+{
+	if (irq)
+		spin_lock_irq(lock);
+	else
+		spin_lock(lock);
+}
+
+static void zs_spin_unlock_cond_irq(spinlock_t *lock, int irq)
+{
+	if (irq)
+		spin_unlock_irq(lock);
+	else
+		spin_unlock(lock);
+}
+
+static int zs_receive_drain(struct zs_port *zport)
+{
+	int loops = 10000;
+
+	while ((read_zsreg(zport, R0) & Rx_CH_AV) && loops--)
+		read_zsdata(zport);
+	return loops;
+}
+
+static int zs_transmit_drain(struct zs_port *zport, int irq)
+{
+	struct zs_scc *scc = zport->scc;
+	int loops = 10000;
+
+	while (!(read_zsreg(zport, R0) & Tx_BUF_EMP) && loops--) {
+		zs_spin_unlock_cond_irq(&scc->zlock, irq);
+		udelay(2);
+		zs_spin_lock_cond_irq(&scc->zlock, irq);
+	}
+	return loops;
+}
+
+static int zs_line_drain(struct zs_port *zport, int irq)
+{
+	struct zs_scc *scc = zport->scc;
+	int loops = 10000;
+
+	while (!(read_zsreg(zport, R1) & ALL_SNT) && loops--) {
+		zs_spin_unlock_cond_irq(&scc->zlock, irq);
+		udelay(2);
+		zs_spin_lock_cond_irq(&scc->zlock, irq);
+	}
+	return loops;
+}
+
+
+static void load_zsregs(struct zs_port *zport, u8 *regs, int irq)
+{
+	/* Let the current transmission finish.  */
+	zs_line_drain(zport, irq);
+	/* Load 'em up.  */
+	write_zsreg(zport, R3, regs[3] & ~RxENABLE);
+	write_zsreg(zport, R5, regs[5] & ~TxENAB);
+	write_zsreg(zport, R4, regs[4]);
+	write_zsreg(zport, R9, regs[9]);
+	write_zsreg(zport, R1, regs[1]);
+	write_zsreg(zport, R2, regs[2]);
+	write_zsreg(zport, R10, regs[10]);
+	write_zsreg(zport, R14, regs[14] & ~BRENABL);
+	write_zsreg(zport, R11, regs[11]);
+	write_zsreg(zport, R12, regs[12]);
+	write_zsreg(zport, R13, regs[13]);
+	write_zsreg(zport, R14, regs[14]);
+	write_zsreg(zport, R15, regs[15]);
+	if (regs[3] & RxENABLE)
+		write_zsreg(zport, R3, regs[3]);
+	if (regs[5] & TxENAB)
+		write_zsreg(zport, R5, regs[5]);
+	return;
+}
+
+
+/*
+ * Status handling routines.
+ */
+
+/*
+ * zs_tx_empty() -- get the transmitter empty status
+ *
+ * Purpose: Let user call ioctl() to get info when the UART physically
+ * 	    is emptied.  On bus types like RS485, the transmitter must
+ * 	    release the bus after transmitting.  This must be done when
+ * 	    the transmit shift register is empty, not be done when the
+ * 	    transmit holding register is empty.  This functionality
+ * 	    allows an RS485 driver to be written in user space.
+ */
+static unsigned int zs_tx_empty(struct uart_port *uport)
+{
+	struct zs_port *zport = to_zport(uport);
+	struct zs_scc *scc = zport->scc;
+	unsigned long flags;
+	u8 status;
+
+	spin_lock_irqsave(&scc->zlock, flags);
+	status = read_zsreg(zport, R1);
+	spin_unlock_irqrestore(&scc->zlock, flags);
+
+	return status & ALL_SNT ? TIOCSER_TEMT : 0;
+}
+
+static unsigned int zs_raw_get_ab_mctrl(struct zs_port *zport_a,
+					struct zs_port *zport_b)
+{
+	u8 status_a, status_b;
+	unsigned int mctrl;
+
+	status_a = read_zsreg(zport_a, R0);
+	status_b = read_zsreg(zport_b, R0);
+
+	mctrl = ((status_b & CTS) ? TIOCM_CTS : 0) |
+		((status_b & DCD) ? TIOCM_CAR : 0) |
+		((status_a & DCD) ? TIOCM_RNG : 0) |
+		((status_a & SYNC_HUNT) ? TIOCM_DSR : 0);
+
+	return mctrl;
+}
+
+static unsigned int zs_raw_get_mctrl(struct zs_port *zport)
+{
+	struct zs_port *zport_a = &zport->scc->zport[ZS_CHAN_A];
+
+	return zport != zport_a ? zs_raw_get_ab_mctrl(zport_a, zport) : 0;
+}
+
+static unsigned int zs_raw_xor_mctrl(struct zs_port *zport)
+{
+	struct zs_port *zport_a = &zport->scc->zport[ZS_CHAN_A];
+	unsigned int mmask, mctrl, delta;
+	u8 mask_a, mask_b;
+
+	if (zport == zport_a)
+		return 0;
+
+	mask_a = zport_a->regs[15];
+	mask_b = zport->regs[15];
+
+	mmask = ((mask_b & CTSIE) ? TIOCM_CTS : 0) |
+		((mask_b & DCDIE) ? TIOCM_CAR : 0) |
+		((mask_a & DCDIE) ? TIOCM_RNG : 0) |
+		((mask_a & SYNCIE) ? TIOCM_DSR : 0);
+
+	mctrl = zport->mctrl;
+	if (mmask) {
+		mctrl &= ~mmask;
+		mctrl |= zs_raw_get_ab_mctrl(zport_a, zport) & mmask;
+	}
+
+	delta = mctrl ^ zport->mctrl;
+	if (delta)
+		zport->mctrl = mctrl;
+
+	return delta;
+}
+
+static unsigned int zs_get_mctrl(struct uart_port *uport)
+{
+	struct zs_port *zport = to_zport(uport);
+	struct zs_scc *scc = zport->scc;
+	unsigned int mctrl;
+
+	spin_lock(&scc->zlock);
+	mctrl = zs_raw_get_mctrl(zport);
+	spin_unlock(&scc->zlock);
+
+	return mctrl;
+}
+
+static void zs_set_mctrl(struct uart_port *uport, unsigned int mctrl)
+{
+	struct zs_port *zport = to_zport(uport);
+	struct zs_scc *scc = zport->scc;
+	struct zs_port *zport_a = &scc->zport[ZS_CHAN_A];
+	u8 oldloop, newloop;
+
+	spin_lock(&scc->zlock);
+	if (zport != zport_a) {
+		if (mctrl & TIOCM_DTR)
+			zport_a->regs[5] |= DTR;
+		else
+			zport_a->regs[5] &= ~DTR;
+		if (mctrl & TIOCM_RTS)
+			zport_a->regs[5] |= RTS;
+		else
+			zport_a->regs[5] &= ~RTS;
+		write_zsreg(zport_a, R5, zport_a->regs[5]);
+	}
+
+	/* Rarely modified, so don't poke at hardware unless necessary. */
+	oldloop = zport->regs[14];
+	newloop = oldloop;
+	if (mctrl & TIOCM_LOOP)
+		newloop |= LOOPBAK;
+	else
+		newloop &= ~LOOPBAK;
+	if (newloop != oldloop) {
+		zport->regs[14] = newloop;
+		write_zsreg(zport, R14, zport->regs[14]);
+	}
+	spin_unlock(&scc->zlock);
+}
+
+static void zs_raw_stop_tx(struct zs_port *zport)
+{
+	write_zsreg(zport, R0, RES_Tx_P);
+	zport->tx_stopped = 1;
+}
+
+static void zs_stop_tx(struct uart_port *uport)
+{
+	struct zs_port *zport = to_zport(uport);
+	struct zs_scc *scc = zport->scc;
+
+	spin_lock(&scc->zlock);
+	zs_raw_stop_tx(zport);
+	spin_unlock(&scc->zlock);
+}
+
+static void zs_raw_transmit_chars(struct zs_port *);
+
+static void zs_start_tx(struct uart_port *uport)
+{
+	struct zs_port *zport = to_zport(uport);
+	struct zs_scc *scc = zport->scc;
+
+	spin_lock(&scc->zlock);
+	if (zport->tx_stopped) {
+		zs_transmit_drain(zport, 0);
+		zport->tx_stopped = 0;
+		zs_raw_transmit_chars(zport);
+	}
+	spin_unlock(&scc->zlock);
+}
+
+static void zs_stop_rx(struct uart_port *uport)
+{
+	struct zs_port *zport = to_zport(uport);
+	struct zs_scc *scc = zport->scc;
+	struct zs_port *zport_a = &scc->zport[ZS_CHAN_A];
+
+	spin_lock(&scc->zlock);
+	zport->regs[15] &= ~BRKIE;
+	zport->regs[1] &= ~(RxINT_MASK | TxINT_ENAB);
+	zport->regs[1] |= RxINT_DISAB;
+
+	if (zport != zport_a) {
+		/* A-side DCD tracks RI and SYNC tracks DSR.  */
+		zport_a->regs[15] &= ~(DCDIE | SYNCIE);
+		write_zsreg(zport_a, R15, zport_a->regs[15]);
+		if (!(zport_a->regs[15] & BRKIE)) {
+			zport_a->regs[1] &= ~EXT_INT_ENAB;
+			write_zsreg(zport_a, R1, zport_a->regs[1]);
+		}
+
+		/* This-side DCD tracks DCD and CTS tracks CTS.  */
+		zport->regs[15] &= ~(DCDIE | CTSIE);
+		zport->regs[1] &= ~EXT_INT_ENAB;
+	} else {
+		/* DCD tracks RI and SYNC tracks DSR for the B side.  */
+		if (!(zport->regs[15] & (DCDIE | SYNCIE)))
+			zport->regs[1] &= ~EXT_INT_ENAB;
+	}
+
+	write_zsreg(zport, R15, zport->regs[15]);
+	write_zsreg(zport, R1, zport->regs[1]);
+	spin_unlock(&scc->zlock);
+}
+
+static void zs_enable_ms(struct uart_port *uport)
+{
+	struct zs_port *zport = to_zport(uport);
+	struct zs_scc *scc = zport->scc;
+	struct zs_port *zport_a = &scc->zport[ZS_CHAN_A];
+
+	if (zport == zport_a)
+		return;
+
+	spin_lock(&scc->zlock);
+
+	/* Clear Ext interrupts if not being handled already.  */
+	if (!(zport_a->regs[1] & EXT_INT_ENAB))
+		write_zsreg(zport_a, R0, RES_EXT_INT);
+
+	/* A-side DCD tracks RI and SYNC tracks DSR.  */
+	zport_a->regs[1] |= EXT_INT_ENAB;
+	zport_a->regs[15] |= DCDIE | SYNCIE;
+
+	/* This-side DCD tracks DCD and CTS tracks CTS.  */
+	zport->regs[15] |= DCDIE | CTSIE;
+
+	zs_raw_xor_mctrl(zport);
+
+	write_zsreg(zport_a, R1, zport_a->regs[1]);
+	write_zsreg(zport_a, R15, zport_a->regs[15]);
+	write_zsreg(zport, R15, zport->regs[15]);
+	spin_unlock(&scc->zlock);
+}
+
+static void zs_break_ctl(struct uart_port *uport, int break_state)
+{
+	struct zs_port *zport = to_zport(uport);
+	struct zs_scc *scc = zport->scc;
+	unsigned long flags;
+
+	spin_lock_irqsave(&scc->zlock, flags);
+	if (break_state == -1)
+		zport->regs[5] |= SND_BRK;
+	else
+		zport->regs[5] &= ~SND_BRK;
+	write_zsreg(zport, R5, zport->regs[5]);
+	spin_unlock_irqrestore(&scc->zlock, flags);
+}
+
+
+/*
+ * Interrupt handling routines.
+ */
+#define Rx_BRK 0x0100			/* BREAK event software flag.  */
+#define Rx_SYS 0x0200			/* SysRq event software flag.  */
+
+static void zs_receive_chars(struct zs_port *zport)
+{
+	struct uart_port *uport = &zport->port;
+	struct zs_scc *scc = zport->scc;
+	struct uart_icount *icount;
+	unsigned int avail, status, ch, flag;
+	int count;
+
+	for (count = 16; count; count--) {
+		spin_lock(&scc->zlock);
+		avail = read_zsreg(zport, R0) & Rx_CH_AV;
+		spin_unlock(&scc->zlock);
+		if (!avail)
+			break;
+
+		spin_lock(&scc->zlock);
+		status = read_zsreg(zport, R1) & (Rx_OVR | FRM_ERR | PAR_ERR);
+		ch = read_zsdata(zport);
+		spin_unlock(&scc->zlock);
+
+		flag = TTY_NORMAL;
+
+		icount = &uport->icount;
+		icount->rx++;
+
+		/* Handle the null char got when BREAK is removed.  */
+		if (!ch)
+			status |= zport->tty_break;
+		if (unlikely(status &
+			     (Rx_OVR | FRM_ERR | PAR_ERR | Rx_SYS | Rx_BRK))) {
+			zport->tty_break = 0;
+
+			/* Reset the error indication.  */
+			if (status & (Rx_OVR | FRM_ERR | PAR_ERR)) {
+				spin_lock(&scc->zlock);
+				write_zsreg(zport, R0, ERR_RES);
+				spin_unlock(&scc->zlock);
+			}
+
+			if (status & (Rx_SYS | Rx_BRK)) {
+				icount->brk++;
+				/* SysRq discards the null char.  */
+				if (status & Rx_SYS)
+					continue;
+			} else if (status & FRM_ERR)
+				icount->frame++;
+			else if (status & PAR_ERR)
+				icount->parity++;
+			if (status & Rx_OVR)
+				icount->overrun++;
+
+			status &= uport->read_status_mask;
+			if (status & Rx_BRK)
+				flag = TTY_BREAK;
+			else if (status & FRM_ERR)
+				flag = TTY_FRAME;
+			else if (status & PAR_ERR)
+				flag = TTY_PARITY;
+		}
+
+		if (uart_handle_sysrq_char(uport, ch))
+			continue;
+
+		uart_insert_char(uport, status, Rx_OVR, ch, flag);
+	}
+
+	tty_flip_buffer_push(uport->info->tty);
+}
+
+static void zs_raw_transmit_chars(struct zs_port *zport)
+{
+	struct circ_buf *xmit = &zport->port.info->xmit;
+
+	/* XON/XOFF chars.  */
+	if (zport->port.x_char) {
+		write_zsdata(zport, zport->port.x_char);
+		zport->port.icount.tx++;
+		zport->port.x_char = 0;
+		return;
+	}
+
+	/* If nothing to do or stopped or hardware stopped.  */
+	if (uart_circ_empty(xmit) || uart_tx_stopped(&zport->port)) {
+		zs_raw_stop_tx(zport);
+		return;
+	}
+
+	/* Send char.  */
+	write_zsdata(zport, xmit->buf[xmit->tail]);
+	xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
+	zport->port.icount.tx++;
+
+	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+		uart_write_wakeup(&zport->port);
+
+	/* Are we are done?  */
+	if (uart_circ_empty(xmit))
+		zs_raw_stop_tx(zport);
+}
+
+static void zs_transmit_chars(struct zs_port *zport)
+{
+	struct zs_scc *scc = zport->scc;
+
+	spin_lock(&scc->zlock);
+	zs_raw_transmit_chars(zport);
+	spin_unlock(&scc->zlock);
+}
+
+static void zs_status_handle(struct zs_port *zport, struct zs_port *zport_a)
+{
+	struct uart_port *uport = &zport->port;
+	struct zs_scc *scc = zport->scc;
+	unsigned int delta;
+	u8 status, brk;
+
+	spin_lock(&scc->zlock);
+
+	/* Get status from Read Register 0.  */
+	status = read_zsreg(zport, R0);
+
+	if (zport->regs[15] & BRKIE) {
+		brk = status & BRK_ABRT;
+		if (brk && !zport->brk) {
+			spin_unlock(&scc->zlock);
+			if (uart_handle_break(uport))
+				zport->tty_break = Rx_SYS;
+			else
+				zport->tty_break = Rx_BRK;
+			spin_lock(&scc->zlock);
+		}
+		zport->brk = brk;
+	}
+
+	if (zport != zport_a) {
+		delta = zs_raw_xor_mctrl(zport);
+		spin_unlock(&scc->zlock);
+
+		if (delta & TIOCM_CTS)
+			uart_handle_cts_change(uport,
+					       zport->mctrl & TIOCM_CTS);
+		if (delta & TIOCM_CAR)
+			uart_handle_dcd_change(uport,
+					       zport->mctrl & TIOCM_CAR);
+		if (delta & TIOCM_RNG)
+			uport->icount.dsr++;
+		if (delta & TIOCM_DSR)
+			uport->icount.rng++;
+
+		if (delta)
+			wake_up_interruptible(&uport->info->delta_msr_wait);
+
+		spin_lock(&scc->zlock);
+	}
+
+	/* Clear the status condition...  */
+	write_zsreg(zport, R0, RES_EXT_INT);
+
+	spin_unlock(&scc->zlock);
+}
+
+/*
+ * This is the Z85C30 driver's generic interrupt routine.
+ */
+static irqreturn_t zs_interrupt(int irq, void *dev_id)
+{
+	struct zs_scc *scc = dev_id;
+	struct zs_port *zport_a = &scc->zport[ZS_CHAN_A];
+	struct zs_port *zport_b = &scc->zport[ZS_CHAN_B];
+	irqreturn_t status = IRQ_NONE;
+	u8 zs_intreg;
+	int count;
+
+	/*
+	 * NOTE: The read register 3, which holds the irq status,
+	 *       does so for both channels on each chip.  Although
+	 *       the status value itself must be read from the A
+	 *       channel and is only valid when read from channel A.
+	 *       Yes... broken hardware...
+	 */
+	for (count = 16; count; count--) {
+		spin_lock(&scc->zlock);
+		zs_intreg = read_zsreg(zport_a, R3);
+		spin_unlock(&scc->zlock);
+		if (!zs_intreg)
+			break;
+
+		/*
+		 * We do not like losing characters, so we prioritise
+		 * interrupt sources a little bit differently than
+		 * the SCC would, was it allowed to.
+		 */
+		if (zs_intreg & CHBRxIP)
+			zs_receive_chars(zport_b);
+		if (zs_intreg & CHARxIP)
+			zs_receive_chars(zport_a);
+		if (zs_intreg & CHBEXT)
+			zs_status_handle(zport_b, zport_a);
+		if (zs_intreg & CHAEXT)
+			zs_status_handle(zport_a, zport_a);
+		if (zs_intreg & CHBTxIP)
+			zs_transmit_chars(zport_b);
+		if (zs_intreg & CHATxIP)
+			zs_transmit_chars(zport_a);
+
+		status = IRQ_HANDLED;
+	}
+
+	return status;
+}
+
+
+/*
+ * Finally, routines used to initialize the serial port.
+ */
+static int zs_startup(struct uart_port *uport)
+{
+	struct zs_port *zport = to_zport(uport);
+	struct zs_scc *scc = zport->scc;
+	unsigned long flags;
+	int irq_guard;
+	int ret;
+
+	irq_guard = atomic_add_return(1, &scc->irq_guard);
+	if (irq_guard == 1) {
+		ret = request_irq(zport->port.irq, zs_interrupt,
+				  IRQF_SHARED, "scc", scc);
+		if (ret) {
+			atomic_add(-1, &scc->irq_guard);
+			printk(KERN_ERR "zs: can't get irq %d\n",
+			       zport->port.irq);
+			return ret;
+		}
+	}
+
+	spin_lock_irqsave(&scc->zlock, flags);
+
+	/* Clear the receive FIFO.  */
+	zs_receive_drain(zport);
+
+	/* Clear the interrupt registers.  */
+	write_zsreg(zport, R0, ERR_RES);
+	write_zsreg(zport, R0, RES_Tx_P);
+	/* But Ext only if not being handled already.  */
+	if (!(zport->regs[1] & EXT_INT_ENAB))
+		write_zsreg(zport, R0, RES_EXT_INT);
+
+	/* Finally, enable sequencing and interrupts.  */
+	zport->regs[1] &= ~RxINT_MASK;
+	zport->regs[1] |= RxINT_ALL | TxINT_ENAB | EXT_INT_ENAB;
+	zport->regs[3] |= RxENABLE;
+	zport->regs[5] |= TxENAB;
+	zport->regs[15] |= BRKIE;
+	write_zsreg(zport, R1, zport->regs[1]);
+	write_zsreg(zport, R3, zport->regs[3]);
+	write_zsreg(zport, R5, zport->regs[5]);
+	write_zsreg(zport, R15, zport->regs[15]);
+
+	/* Record the current state of RR0.  */
+	zport->mctrl = zs_raw_get_mctrl(zport);
+	zport->brk = read_zsreg(zport, R0) & BRK_ABRT;
+
+	zport->tx_stopped = 1;
+
+	spin_unlock_irqrestore(&scc->zlock, flags);
+
+	return 0;
+}
+
+static void zs_shutdown(struct uart_port *uport)
+{
+	struct zs_port *zport = to_zport(uport);
+	struct zs_scc *scc = zport->scc;
+	unsigned long flags;
+	int irq_guard;
+
+	spin_lock_irqsave(&scc->zlock, flags);
+
+	zport->regs[5] &= ~TxENAB;
+	zport->regs[3] &= ~RxENABLE;
+	write_zsreg(zport, R5, zport->regs[5]);
+	write_zsreg(zport, R3, zport->regs[3]);
+
+	spin_unlock_irqrestore(&scc->zlock, flags);
+
+	irq_guard = atomic_add_return(-1, &scc->irq_guard);
+	if (!irq_guard)
+		free_irq(zport->port.irq, scc);
+}
+
+
+static void zs_reset(struct zs_port *zport)
+{
+	struct zs_scc *scc = zport->scc;
+	int irq;
+	unsigned long flags;
+
+	spin_lock_irqsave(&scc->zlock, flags);
+	irq = !irqs_disabled_flags(flags);
+	if (!scc->initialised) {
+		/* Reset the pointer first, just in case...  */
+		read_zsreg(zport, R0);
+		/* And let the current transmission finish.  */
+		zs_line_drain(zport, irq);
+		write_zsreg(zport, R9, FHWRES);
+		udelay(10);
+		write_zsreg(zport, R9, 0);
+		scc->initialised = 1;
+	}
+	load_zsregs(zport, zport->regs, irq);
+	spin_unlock_irqrestore(&scc->zlock, flags);
+}
+
+static void zs_set_termios(struct uart_port *uport, struct ktermios *termios,
+			   struct ktermios *old_termios)
+{
+	struct zs_port *zport = to_zport(uport);
+	struct zs_scc *scc = zport->scc;
+	struct zs_port *zport_a = &scc->zport[ZS_CHAN_A];
+	int irq;
+	unsigned int baud, brg;
+	unsigned long flags;
+
+	spin_lock_irqsave(&scc->zlock, flags);
+	irq = !irqs_disabled_flags(flags);
+
+	/* Byte size.  */
+	zport->regs[3] &= ~RxNBITS_MASK;
+	zport->regs[5] &= ~TxNBITS_MASK;
+	switch (termios->c_cflag & CSIZE) {
+	case CS5:
+		zport->regs[3] |= Rx5;
+		zport->regs[5] |= Tx5;
+		break;
+	case CS6:
+		zport->regs[3] |= Rx6;
+		zport->regs[5] |= Tx6;
+		break;
+	case CS7:
+		zport->regs[3] |= Rx7;
+		zport->regs[5] |= Tx7;
+		break;
+	case CS8:
+	default:
+		zport->regs[3] |= Rx8;
+		zport->regs[5] |= Tx8;
+		break;
+	}
+
+	/* Parity and stop bits.  */
+	zport->regs[4] &= ~(XCLK_MASK | SB_MASK | PAR_ENA | PAR_EVEN);
+	if (termios->c_cflag & CSTOPB)
+		zport->regs[4] |= SB2;
+	else
+		zport->regs[4] |= SB1;
+	if (termios->c_cflag & PARENB)
+		zport->regs[4] |= PAR_ENA;
+	if (!(termios->c_cflag & PARODD))
+		zport->regs[4] |= PAR_EVEN;
+	switch (zport->clk_mode) {
+	case 64:
+		zport->regs[4] |= X64CLK;
+		break;
+	case 32:
+		zport->regs[4] |= X32CLK;
+		break;
+	case 16:
+		zport->regs[4] |= X16CLK;
+		break;
+	case 1:
+		zport->regs[4] |= X1CLK;
+		break;
+	default:
+		BUG();
+	}
+
+	baud = uart_get_baud_rate(uport, termios, old_termios, 0,
+				  uport->uartclk / zport->clk_mode / 4);
+
+	brg = ZS_BPS_TO_BRG(baud, uport->uartclk / zport->clk_mode);
+	zport->regs[12] = brg & 0xff;
+	zport->regs[13] = (brg >> 8) & 0xff;
+
+	uart_update_timeout(uport, termios->c_cflag, baud);
+
+	uport->read_status_mask = Rx_OVR;
+	if (termios->c_iflag & INPCK)
+		uport->read_status_mask |= FRM_ERR | PAR_ERR;
+	if (termios->c_iflag & (BRKINT | PARMRK))
+		uport->read_status_mask |= Rx_BRK;
+
+	uport->ignore_status_mask = 0;
+	if (termios->c_iflag & IGNPAR)
+		uport->ignore_status_mask |= FRM_ERR | PAR_ERR;
+	if (termios->c_iflag & IGNBRK) {
+		uport->ignore_status_mask |= Rx_BRK;
+		if (termios->c_iflag & IGNPAR)
+			uport->ignore_status_mask |= Rx_OVR;
+	}
+
+	if (termios->c_cflag & CREAD)
+		zport->regs[3] |= RxENABLE;
+	else
+		zport->regs[3] &= ~RxENABLE;
+
+	if (zport != zport_a) {
+		if (!(termios->c_cflag & CLOCAL)) {
+			zport->regs[15] |= DCDIE;
+		} else
+			zport->regs[15] &= ~DCDIE;
+		if (termios->c_cflag & CRTSCTS) {
+			zport->regs[15] |= CTSIE;
+		} else
+			zport->regs[15] &= ~CTSIE;
+		zs_raw_xor_mctrl(zport);
+	}
+
+	/* Load up the new values.  */
+	load_zsregs(zport, zport->regs, irq);
+
+	spin_unlock_irqrestore(&scc->zlock, flags);
+}
+
+
+static const char *zs_type(struct uart_port *uport)
+{
+	return "Z85C30 SCC";
+}
+
+static void zs_release_port(struct uart_port *uport)
+{
+	iounmap(uport->membase);
+	uport->membase = 0;
+	release_mem_region(uport->mapbase, ZS_CHAN_IO_SIZE);
+}
+
+static int zs_map_port(struct uart_port *uport)
+{
+	if (!uport->membase)
+		uport->membase = ioremap_nocache(uport->mapbase,
+						 ZS_CHAN_IO_SIZE);
+	if (!uport->membase) {
+		printk(KERN_ERR "zs: Cannot map MMIO\n");
+		return -ENOMEM;
+	}
+	return 0;
+}
+
+static int zs_request_port(struct uart_port *uport)
+{
+	int ret;
+
+	if (!request_mem_region(uport->mapbase, ZS_CHAN_IO_SIZE, "scc")) {
+		printk(KERN_ERR "zs: Unable to reserve MMIO resource\n");
+		return -EBUSY;
+	}
+	ret = zs_map_port(uport);
+	if (ret) {
+		release_mem_region(uport->mapbase, ZS_CHAN_IO_SIZE);
+		return ret;
+	}
+	return 0;
+}
+
+static void zs_config_port(struct uart_port *uport, int flags)
+{
+	struct zs_port *zport = to_zport(uport);
+
+	if (flags & UART_CONFIG_TYPE) {
+		if (zs_request_port(uport))
+			return;
+
+		uport->type = PORT_ZS;
+
+		zs_reset(zport);
+	}
+}
+
+static int zs_verify_port(struct uart_port *uport, struct serial_struct *ser)
+{
+	struct zs_port *zport = to_zport(uport);
+	int ret = 0;
+
+	if (ser->type != PORT_UNKNOWN && ser->type != PORT_ZS)
+		ret = -EINVAL;
+	if (ser->irq != uport->irq)
+		ret = -EINVAL;
+	if (ser->baud_base != uport->uartclk / zport->clk_mode / 4)
+		ret = -EINVAL;
+	return ret;
+}
+
+
+static struct uart_ops zs_ops = {
+	.tx_empty	= zs_tx_empty,
+	.set_mctrl	= zs_set_mctrl,
+	.get_mctrl	= zs_get_mctrl,
+	.stop_tx	= zs_stop_tx,
+	.start_tx	= zs_start_tx,
+	.stop_rx	= zs_stop_rx,
+	.enable_ms	= zs_enable_ms,
+	.break_ctl	= zs_break_ctl,
+	.startup	= zs_startup,
+	.shutdown	= zs_shutdown,
+	.set_termios	= zs_set_termios,
+	.type		= zs_type,
+	.release_port	= zs_release_port,
+	.request_port	= zs_request_port,
+	.config_port	= zs_config_port,
+	.verify_port	= zs_verify_port,
+};
+
+/*
+ * Initialize Z85C30 port structures.
+ */
+static int __init zs_probe_sccs(void)
+{
+	static int probed;
+	struct zs_parms zs_parms;
+	int chip, side, irq;
+	int n_chips = 0;
+	int i;
+
+	if (probed)
+		return 0;
+
+	irq = dec_interrupt[DEC_IRQ_SCC0];
+	if (irq >= 0) {
+		zs_parms.scc[n_chips] = IOASIC_SCC0;
+		zs_parms.irq[n_chips] = dec_interrupt[DEC_IRQ_SCC0];
+		n_chips++;
+	}
+	irq = dec_interrupt[DEC_IRQ_SCC1];
+	if (irq >= 0) {
+		zs_parms.scc[n_chips] = IOASIC_SCC1;
+		zs_parms.irq[n_chips] = dec_interrupt[DEC_IRQ_SCC1];
+		n_chips++;
+	}
+	if (!n_chips)
+		return -ENXIO;
+
+	probed = 1;
+
+	for (chip = 0; chip < n_chips; chip++) {
+		spin_lock_init(&zs_sccs[chip].zlock);
+		for (side = 0; side < ZS_NUM_CHAN; side++) {
+			struct zs_port *zport = &zs_sccs[chip].zport[side];
+			struct uart_port *uport = &zport->port;
+
+			zport->scc	= &zs_sccs[chip];
+			zport->clk_mode	= 16;
+
+			uport->irq	= zs_parms.irq[chip];
+			uport->uartclk	= ZS_CLOCK;
+			uport->fifosize	= 1;
+			uport->iotype	= UPIO_MEM;
+			uport->flags	= UPF_BOOT_AUTOCONF;
+			uport->ops	= &zs_ops;
+			uport->line	= chip * ZS_NUM_CHAN + side;
+			uport->mapbase	= dec_kn_slot_base +
+					  zs_parms.scc[chip] +
+					  (side ^ ZS_CHAN_B) * ZS_CHAN_IO_SIZE;
+
+			for (i = 0; i < ZS_NUM_REGS; i++)
+				zport->regs[i] = zs_init_regs[i];
+		}
+	}
+
+	return 0;
+}
+
+
+#ifdef CONFIG_SERIAL_ZS_CONSOLE
+static void zs_console_putchar(struct uart_port *uport, int ch)
+{
+	struct zs_port *zport = to_zport(uport);
+	struct zs_scc *scc = zport->scc;
+	int irq;
+	unsigned long flags;
+
+	spin_lock_irqsave(&scc->zlock, flags);
+	irq = !irqs_disabled_flags(flags);
+	if (zs_transmit_drain(zport, irq))
+		write_zsdata(zport, ch);
+	spin_unlock_irqrestore(&scc->zlock, flags);
+}
+
+/*
+ * Print a string to the serial port trying not to disturb
+ * any possible real use of the port...
+ */
+static void zs_console_write(struct console *co, const char *s,
+			     unsigned int count)
+{
+	int chip = co->index / ZS_NUM_CHAN, side = co->index % ZS_NUM_CHAN;
+	struct zs_port *zport = &zs_sccs[chip].zport[side];
+	struct zs_scc *scc = zport->scc;
+	unsigned long flags;
+	u8 txint, txenb;
+	int irq;
+
+	/* Disable transmit interrupts and enable the transmitter. */
+	spin_lock_irqsave(&scc->zlock, flags);
+	txint = zport->regs[1];
+	txenb = zport->regs[5];
+	if (txint & TxINT_ENAB) {
+		zport->regs[1] = txint & ~TxINT_ENAB;
+		write_zsreg(zport, R1, zport->regs[1]);
+	}
+	if (!(txenb & TxENAB)) {
+		zport->regs[5] = txenb | TxENAB;
+		write_zsreg(zport, R5, zport->regs[5]);
+	}
+	spin_unlock_irqrestore(&scc->zlock, flags);
+
+	uart_console_write(&zport->port, s, count, zs_console_putchar);
+
+	/* Restore transmit interrupts and the transmitter enable. */
+	spin_lock_irqsave(&scc->zlock, flags);
+	irq = !irqs_disabled_flags(flags);
+	zs_line_drain(zport, irq);
+	if (!(txenb & TxENAB)) {
+		zport->regs[5] &= ~TxENAB;
+		write_zsreg(zport, R5, zport->regs[5]);
+	}
+	if (txint & TxINT_ENAB) {
+		zport->regs[1] |= TxINT_ENAB;
+		write_zsreg(zport, R1, zport->regs[1]);
+	}
+	spin_unlock_irqrestore(&scc->zlock, flags);
+}
+
+/*
+ * Setup serial console baud/bits/parity.  We do two things here:
+ * - construct a cflag setting for the first uart_open()
+ * - initialise the serial port
+ * Return non-zero if we didn't find a serial port.
+ */
+static int __init zs_console_setup(struct console *co, char *options)
+{
+	int chip = co->index / ZS_NUM_CHAN, side = co->index % ZS_NUM_CHAN;
+	struct zs_port *zport = &zs_sccs[chip].zport[side];
+	struct uart_port *uport = &zport->port;
+	int baud = 9600;
+	int bits = 8;
+	int parity = 'n';
+	int flow = 'n';
+	int ret;
+
+	ret = zs_map_port(uport);
+	if (ret)
+		return ret;
+
+	zs_reset(zport);
+
+	if (options)
+		uart_parse_options(options, &baud, &parity, &bits, &flow);
+	return uart_set_options(uport, co, baud, parity, bits, flow);
+}
+
+static struct uart_driver zs_reg;
+static struct console zs_console = {
+	.name	= "ttyS",
+	.write	= zs_console_write,
+	.device	= uart_console_device,
+	.setup	= zs_console_setup,
+	.flags	= CON_PRINTBUFFER,
+	.index	= -1,
+	.data	= &zs_reg,
+};
+
+/*
+ *	Register console.
+ */
+static int __init zs_serial_console_init(void)
+{
+	int ret;
+
+	ret = zs_probe_sccs();
+	if (ret)
+		return ret;
+	register_console(&zs_console);
+
+	return 0;
+}
+
+console_initcall(zs_serial_console_init);
+
+#define SERIAL_ZS_CONSOLE	&zs_console
+#else
+#define SERIAL_ZS_CONSOLE	NULL
+#endif /* CONFIG_SERIAL_ZS_CONSOLE */
+
+static struct uart_driver zs_reg = {
+	.owner			= THIS_MODULE,
+	.driver_name		= "serial",
+	.dev_name		= "ttyS",
+	.major			= TTY_MAJOR,
+	.minor			= 64,
+	.nr			= ZS_NUM_SCCS * ZS_NUM_CHAN,
+	.cons			= SERIAL_ZS_CONSOLE,
+};
+
+/* zs_init inits the driver. */
+static int __init zs_init(void)
+{
+	int i, ret;
+
+	pr_info("%s%s\n", zs_name, zs_version);
+
+	/* Find out how many Z85C30 SCCs we have.  */
+	ret = zs_probe_sccs();
+	if (ret)
+		return ret;
+
+	ret = uart_register_driver(&zs_reg);
+	if (ret)
+		return ret;
+
+	for (i = 0; i < ZS_NUM_SCCS * ZS_NUM_CHAN; i++) {
+		struct zs_scc *scc = &zs_sccs[i / ZS_NUM_CHAN];
+		struct zs_port *zport = &scc->zport[i % ZS_NUM_CHAN];
+		struct uart_port *uport = &zport->port;
+
+		if (zport->scc)
+			uart_add_one_port(&zs_reg, uport);
+	}
+
+	return 0;
+}
+
+static void __exit zs_exit(void)
+{
+	int i;
+
+	for (i = ZS_NUM_SCCS * ZS_NUM_CHAN - 1; i >= 0; i--) {
+		struct zs_scc *scc = &zs_sccs[i / ZS_NUM_CHAN];
+		struct zs_port *zport = &scc->zport[i % ZS_NUM_CHAN];
+		struct uart_port *uport = &zport->port;
+
+		if (zport->scc)
+			uart_remove_one_port(&zs_reg, uport);
+	}
+
+	uart_unregister_driver(&zs_reg);
+}
+
+module_init(zs_init);
+module_exit(zs_exit);