sunzilog.c

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/*
 * sunzilog.c
 *
 * Driver for Zilog serial chips found on Sun workstations and
 * servers.  This driver could actually be made more generic.
 *
 * This is based on the old drivers/sbus/char/zs.c code.  A lot
 * of code has been simply moved over directly from there but
 * much has been rewritten.  Credits therefore go out to Eddie
 * C. Dost, Pete Zaitcev, Ted Ts'o and Alex Buell for their
 * work there.
 *
 *  Copyright (C) 2002 David S. Miller ([e-mail])
 */

#include <linux/config.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/delay.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/major.h>
#include <linux/string.h>
#include <linux/ptrace.h>
#include <linux/ioport.h>
#include <linux/slab.h>
#include <linux/circ_buf.h>
#include <linux/serial.h>
#include <linux/sysrq.h>
#include <linux/console.h>
#include <linux/spinlock.h>
#ifdef CONFIG_SERIO
#include <linux/serio.h>
#endif
#include <linux/init.h>

#include <asm/io.h>
#include <asm/irq.h>
#ifdef CONFIG_SPARC64
#include <asm/fhc.h>
#endif
#include <asm/sbus.h>

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

#include <linux/serial_core.h>

#include "suncore.h"
#include "sunzilog.h"

/* On 32-bit sparcs we need to delay after register accesses
 * to accommodate sun4 systems, but we do not need to flush writes.
 * On 64-bit sparc we only need to flush single writes to ensure
 * completion.
 */
#ifndef CONFIG_SPARC64
#define ZSDELAY()		udelay(5)
#define ZSDELAY_LONG()		udelay(20)
#define ZS_WSYNC(channel)	do { } while (0)
#else
#define ZSDELAY()
#define ZSDELAY_LONG()
#define ZS_WSYNC(__channel) \
	sbus_readb(&((__channel)->control))
#endif

static int num_sunzilog;
#define NUM_SUNZILOG	num_sunzilog
#define NUM_CHANNELS	(NUM_SUNZILOG * 2)

#define KEYBOARD_LINE 0x2
#define MOUSE_LINE    0x3

#define ZS_CLOCK		4915200 /* Zilog input clock rate. */
#define ZS_CLOCK_DIVISOR	16      /* Divisor this driver uses. */

/*
 * We wrap our port structure around the generic uart_port.
 */
struct uart_sunzilog_port {
	struct uart_port		port;

	/* IRQ servicing chain.  */
	struct uart_sunzilog_port	*next;

	/* Current values of Zilog write registers.  */
	unsigned char			curregs[NUM_ZSREGS];

	unsigned int			flags;
#define SUNZILOG_FLAG_CONS_KEYB		0x00000001
#define SUNZILOG_FLAG_CONS_MOUSE	0x00000002
#define SUNZILOG_FLAG_IS_CONS		0x00000004
#define SUNZILOG_FLAG_IS_KGDB		0x00000008
#define SUNZILOG_FLAG_MODEM_STATUS	0x00000010
#define SUNZILOG_FLAG_IS_CHANNEL_A	0x00000020
#define SUNZILOG_FLAG_REGS_HELD		0x00000040
#define SUNZILOG_FLAG_TX_STOPPED	0x00000080
#define SUNZILOG_FLAG_TX_ACTIVE		0x00000100

	unsigned int cflag;

	unsigned char			parity_mask;
	unsigned char			prev_status;

#ifdef CONFIG_SERIO
	struct serio			*serio;
	int				serio_open;
#endif
};

#define ZILOG_CHANNEL_FROM_PORT(PORT)	((struct zilog_channel *)((PORT)->membase))
#define UART_ZILOG(PORT)		((struct uart_sunzilog_port *)(PORT))

#define ZS_IS_KEYB(UP)	((UP)->flags & SUNZILOG_FLAG_CONS_KEYB)
#define ZS_IS_MOUSE(UP)	((UP)->flags & SUNZILOG_FLAG_CONS_MOUSE)
#define ZS_IS_CONS(UP)	((UP)->flags & SUNZILOG_FLAG_IS_CONS)
#define ZS_IS_KGDB(UP)	((UP)->flags & SUNZILOG_FLAG_IS_KGDB)
#define ZS_WANTS_MODEM_STATUS(UP)	((UP)->flags & SUNZILOG_FLAG_MODEM_STATUS)
#define ZS_IS_CHANNEL_A(UP)	((UP)->flags & SUNZILOG_FLAG_IS_CHANNEL_A)
#define ZS_REGS_HELD(UP)	((UP)->flags & SUNZILOG_FLAG_REGS_HELD)
#define ZS_TX_STOPPED(UP)	((UP)->flags & SUNZILOG_FLAG_TX_STOPPED)
#define ZS_TX_ACTIVE(UP)	((UP)->flags & SUNZILOG_FLAG_TX_ACTIVE)

/* Reading and writing Zilog8530 registers.  The delays are to make this
 * driver work on the Sun4 which needs a settling delay after each chip
 * register access, other machines handle this in hardware via auxiliary
 * flip-flops which implement the settle time we do in software.
 *
 * The port lock must be held and local IRQs must be disabled
 * when {read,write}_zsreg is invoked.
 */
static unsigned char read_zsreg(struct zilog_channel *channel,
				unsigned char reg)
{
	unsigned char retval;

	sbus_writeb(reg, &channel->control);
	ZSDELAY();
	retval = sbus_readb(&channel->control);
	ZSDELAY();

	return retval;
}

static void write_zsreg(struct zilog_channel *channel,
			unsigned char reg, unsigned char value)
{
	sbus_writeb(reg, &channel->control);
	ZSDELAY();
	sbus_writeb(value, &channel->control);
	ZSDELAY();
}

static void sunzilog_clear_fifo(struct zilog_channel *channel)
{
	int i;

	for (i = 0; i < 32; i++) {
		unsigned char regval;

		regval = sbus_readb(&channel->control);
		ZSDELAY();
		if (regval & Rx_CH_AV)
			break;

		regval = read_zsreg(channel, R1);
		sbus_readb(&channel->data);
		ZSDELAY();

		if (regval & (PAR_ERR | Rx_OVR | CRC_ERR)) {
			sbus_writeb(ERR_RES, &channel->control);
			ZSDELAY();
			ZS_WSYNC(channel);
		}
	}
}

/* This function must only be called when the TX is not busy.  The UART
 * port lock must be held and local interrupts disabled.
 */
static void __load_zsregs(struct zilog_channel *channel, unsigned char *regs)
{
	int i;

	/* Let pending transmits finish.  */
	for (i = 0; i < 1000; i++) {
		unsigned char stat = read_zsreg(channel, R1);
		if (stat & ALL_SNT)
			break;
		udelay(100);
	}

	sbus_writeb(ERR_RES, &channel->control);
	ZSDELAY();
	ZS_WSYNC(channel);

	sunzilog_clear_fifo(channel);

	/* Disable all interrupts.  */
	write_zsreg(channel, R1,
		    regs[R1] & ~(RxINT_MASK | TxINT_ENAB | EXT_INT_ENAB));

	/* Set parity, sync config, stop bits, and clock divisor.  */
	write_zsreg(channel, R4, regs[R4]);

	/* Set misc. TX/RX control bits.  */
	write_zsreg(channel, R10, regs[R10]);

	/* Set TX/RX controls sans the enable bits.  */
	write_zsreg(channel, R3, regs[R3] & ~RxENAB);
	write_zsreg(channel, R5, regs[R5] & ~TxENAB);

	/* Synchronous mode config.  */
	write_zsreg(channel, R6, regs[R6]);
	write_zsreg(channel, R7, regs[R7]);

	/* Don't mess with the interrupt vector (R2, unused by us) and
	 * master interrupt control (R9).  We make sure this is setup
	 * properly at probe time then never touch it again.
	 */

	/* Disable baud generator.  */
	write_zsreg(channel, R14, regs[R14] & ~BRENAB);

	/* Clock mode control.  */
	write_zsreg(channel, R11, regs[R11]);

	/* Lower and upper byte of baud rate generator divisor.  */
	write_zsreg(channel, R12, regs[R12]);
	write_zsreg(channel, R13, regs[R13]);
	
	/* Now rewrite R14, with BRENAB (if set).  */
	write_zsreg(channel, R14, regs[R14]);

	/* External status interrupt control.  */
	write_zsreg(channel, R15, regs[R15]);

	/* Reset external status interrupts.  */
	write_zsreg(channel, R0, RES_EXT_INT);
	write_zsreg(channel, R0, RES_EXT_INT);

	/* Rewrite R3/R5, this time without enables masked.  */
	write_zsreg(channel, R3, regs[R3]);
	write_zsreg(channel, R5, regs[R5]);

	/* Rewrite R1, this time without IRQ enabled masked.  */
	write_zsreg(channel, R1, regs[R1]);
}

/* Reprogram the Zilog channel HW registers with the copies found in the
 * software state struct.  If the transmitter is busy, we defer this update
 * until the next TX complete interrupt.  Else, we do it right now.
 *
 * The UART port lock must be held and local interrupts disabled.
 */
static void sunzilog_maybe_update_regs(struct uart_sunzilog_port *up,
				       struct zilog_channel *channel)
{
	if (!ZS_REGS_HELD(up)) {
		if (ZS_TX_ACTIVE(up)) {
			up->flags |= SUNZILOG_FLAG_REGS_HELD;
		} else {
			__load_zsregs(channel, up->curregs);
		}
	}
}

static void sunzilog_change_mouse_baud(struct uart_sunzilog_port *up)
{
	unsigned int cur_cflag = up->cflag;
	int brg, new_baud;

	up->cflag &= ~CBAUD;
	up->cflag |= suncore_mouse_baud_cflag_next(cur_cflag, &new_baud);

	brg = BPS_TO_BRG(new_baud, ZS_CLOCK / ZS_CLOCK_DIVISOR);
	up->curregs[R12] = (brg & 0xff);
	up->curregs[R13] = (brg >> 8) & 0xff;
	sunzilog_maybe_update_regs(up, ZILOG_CHANNEL_FROM_PORT(&up->port));
}

static void sunzilog_kbdms_receive_chars(struct uart_sunzilog_port *up,
					 unsigned char ch, int is_break,
					 struct pt_regs *regs)
{
	if (ZS_IS_KEYB(up)) {
		/* Stop-A is handled by drivers/char/keyboard.c now. */
#ifdef CONFIG_SERIO
		if (up->serio_open)
			serio_interrupt(up->serio, ch, 0, regs);
#endif
	} else if (ZS_IS_MOUSE(up)) {
		int ret = suncore_mouse_baud_detection(ch, is_break);

		switch (ret) {
		case 2:
			sunzilog_change_mouse_baud(up);
			/* fallthru */
		case 1:
			break;

		case 0:
#ifdef CONFIG_SERIO
			if (up->serio_open)
				serio_interrupt(up->serio, ch, 0, regs);
#endif
			break;
		};
	}
}

static struct tty_struct *
sunzilog_receive_chars(struct uart_sunzilog_port *up,
		       struct zilog_channel *channel,
		       struct pt_regs *regs)
{
	struct tty_struct *tty;
	unsigned char ch, r1;

	tty = NULL;
	if (up->port.info != NULL &&		/* Unopened serial console */
	    up->port.info->tty != NULL)		/* Keyboard || mouse */
		tty = up->port.info->tty;

	for (;;) {

		r1 = read_zsreg(channel, R1);
		if (r1 & (PAR_ERR | Rx_OVR | CRC_ERR)) {
			sbus_writeb(ERR_RES, &channel->control);
			ZSDELAY();
			ZS_WSYNC(channel);
		}

		ch = sbus_readb(&channel->control);
		ZSDELAY();

		/* This funny hack depends upon BRK_ABRT not interfering
		 * with the other bits we care about in R1.
		 */
		if (ch & BRK_ABRT)
			r1 |= BRK_ABRT;

		if (!(ch & Rx_CH_AV))
			break;

		ch = sbus_readb(&channel->data);
		ZSDELAY();

		ch &= up->parity_mask;

		if (unlikely(ZS_IS_KEYB(up)) || unlikely(ZS_IS_MOUSE(up))) {
			sunzilog_kbdms_receive_chars(up, ch, 0, regs);
			continue;
		}

		if (tty == NULL) {
			uart_handle_sysrq_char(&up->port, ch, regs);
			continue;
		}

		if (unlikely(tty->flip.count >= TTY_FLIPBUF_SIZE)) {
			tty->flip.work.func((void *)tty);
			/*
			 * The 8250 bails out of the loop here,
			 * but we need to read everything, or die.
			 */
			if (tty->flip.count >= TTY_FLIPBUF_SIZE)
				continue;
		}

		/* A real serial line, record the character and status.  */
		*tty->flip.char_buf_ptr = ch;
		*tty->flip.flag_buf_ptr = TTY_NORMAL;
		up->port.icount.rx++;
		if (r1 & (BRK_ABRT | PAR_ERR | Rx_OVR | CRC_ERR)) {
			if (r1 & BRK_ABRT) {
				r1 &= ~(PAR_ERR | CRC_ERR);
				up->port.icount.brk++;
				if (uart_handle_break(&up->port))
					continue;
			}
			else if (r1 & PAR_ERR)
				up->port.icount.parity++;
			else if (r1 & CRC_ERR)
				up->port.icount.frame++;
			if (r1 & Rx_OVR)
				up->port.icount.overrun++;
			r1 &= up->port.read_status_mask;
			if (r1 & BRK_ABRT)
				*tty->flip.flag_buf_ptr = TTY_BREAK;
			else if (r1 & PAR_ERR)
				*tty->flip.flag_buf_ptr = TTY_PARITY;
			else if (r1 & CRC_ERR)
				*tty->flip.flag_buf_ptr = TTY_FRAME;
		}
		if (uart_handle_sysrq_char(&up->port, ch, regs))
			continue;

		if (up->port.ignore_status_mask == 0xff ||
		    (r1 & up->port.ignore_status_mask) == 0) {
			tty->flip.flag_buf_ptr++;
			tty->flip.char_buf_ptr++;
			tty->flip.count++;
		}
		if ((r1 & Rx_OVR) &&
		    tty->flip.count < TTY_FLIPBUF_SIZE) {
			*tty->flip.flag_buf_ptr = TTY_OVERRUN;
			tty->flip.flag_buf_ptr++;
			tty->flip.char_buf_ptr++;
			tty->flip.count++;
		}
	}

	return tty;
}

static void sunzilog_status_handle(struct uart_sunzilog_port *up,
				   struct zilog_channel *channel,
				   struct pt_regs *regs)
{
	unsigned char status;

	status = sbus_readb(&channel->control);
	ZSDELAY();

	sbus_writeb(RES_EXT_INT, &channel->control);
	ZSDELAY();
	ZS_WSYNC(channel);

	if (status & BRK_ABRT) {
		if (ZS_IS_MOUSE(up))
			sunzilog_kbdms_receive_chars(up, 0, 1, regs);
		if (ZS_IS_CONS(up)) {
			/* Wait for BREAK to deassert to avoid potentially
			 * confusing the PROM.
			 */
			while (1) {
				status = sbus_readb(&channel->control);
				ZSDELAY();
				if (!(status & BRK_ABRT))
					break;
			}
			sun_do_break();
			return;
		}
	}

	if (ZS_WANTS_MODEM_STATUS(up)) {
		if (status & SYNC)
			up->port.icount.dsr++;

		/* The Zilog just gives us an interrupt when DCD/CTS/etc. change.
		 * But it does not tell us which bit has changed, we have to keep
		 * track of this ourselves.
		 */
		if ((status ^ up->prev_status) ^ DCD)
			uart_handle_dcd_change(&up->port,
					       (status & DCD));
		if ((status ^ up->prev_status) ^ CTS)
			uart_handle_cts_change(&up->port,
					       (status & CTS));

		wake_up_interruptible(&up->port.info->delta_msr_wait);
	}

	up->prev_status = status;
}

static void sunzilog_transmit_chars(struct uart_sunzilog_port *up,
				    struct zilog_channel *channel)
{
	struct circ_buf *xmit;

	if (ZS_IS_CONS(up)) {
		unsigned char status = sbus_readb(&channel->control);
		ZSDELAY();

		/* TX still busy?  Just wait for the next TX done interrupt.
		 *
		 * It can occur because of how we do serial console writes.  It would
		 * be nice to transmit console writes just like we normally would for
		 * a TTY line. (ie. buffered and TX interrupt driven).  That is not
		 * easy because console writes cannot sleep.  One solution might be
		 * to poll on enough port->xmit space becomming free.  -DaveM
		 */
		if (!(status & Tx_BUF_EMP))
			return;
	}

	up->flags &= ~SUNZILOG_FLAG_TX_ACTIVE;

	if (ZS_REGS_HELD(up)) {
		__load_zsregs(channel, up->curregs);
		up->flags &= ~SUNZILOG_FLAG_REGS_HELD;
	}

	if (ZS_TX_STOPPED(up)) {
		up->flags &= ~SUNZILOG_FLAG_TX_STOPPED;
		goto ack_tx_int;
	}

	if (up->port.x_char) {
		up->flags |= SUNZILOG_FLAG_TX_ACTIVE;
		sbus_writeb(up->port.x_char, &channel->data);
		ZSDELAY();
		ZS_WSYNC(channel);

		up->port.icount.tx++;
		up->port.x_char = 0;
		return;
	}

	if (up->port.info == NULL)
		goto ack_tx_int;
	xmit = &up->port.info->xmit;
	if (uart_circ_empty(xmit)) {
		uart_write_wakeup(&up->port);
		goto ack_tx_int;
	}
	if (uart_tx_stopped(&up->port))
		goto ack_tx_int;

	up->flags |= SUNZILOG_FLAG_TX_ACTIVE;
	sbus_writeb(xmit->buf[xmit->tail], &channel->data);
	ZSDELAY();
	ZS_WSYNC(channel);

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

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

	return;

ack_tx_int:
	sbus_writeb(RES_Tx_P, &channel->control);
	ZSDELAY();
	ZS_WSYNC(channel);
}

static irqreturn_t sunzilog_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
	struct uart_sunzilog_port *up = dev_id;

	while (up) {
		struct zilog_channel *channel
			= ZILOG_CHANNEL_FROM_PORT(&up->port);
		struct tty_struct *tty;
		unsigned char r3;

		spin_lock(&up->port.lock);
		r3 = read_zsreg(channel, R3);

		/* Channel A */
		tty = NULL;
		if (r3 & (CHAEXT | CHATxIP | CHARxIP)) {
			sbus_writeb(RES_H_IUS, &channel->control);
			ZSDELAY();
			ZS_WSYNC(channel);

			if (r3 & CHARxIP)
				tty = sunzilog_receive_chars(up, channel, regs);
			if (r3 & CHAEXT)
				sunzilog_status_handle(up, channel, regs);
			if (r3 & CHATxIP)
				sunzilog_transmit_chars(up, channel);
		}
		spin_unlock(&up->port.lock);

		if (tty)
			tty_flip_buffer_push(tty);

		/* Channel B */
		up = up->next;
		channel = ZILOG_CHANNEL_FROM_PORT(&up->port);

		spin_lock(&up->port.lock);
		tty = NULL;
		if (r3 & (CHBEXT | CHBTxIP | CHBRxIP)) {
			sbus_writeb(RES_H_IUS, &channel->control);
			ZSDELAY();
			ZS_WSYNC(channel);

			if (r3 & CHBRxIP)
				tty = sunzilog_receive_chars(up, channel, regs);
			if (r3 & CHBEXT)