ip22zilog.c

linux 内核源代码

/*
 * Driver for Zilog serial chips found on SGI workstations and
 * servers.  This driver could actually be made more generic.
 *
 * This is based on the drivers/serial/sunzilog.c code as of 2.6.0-test7 and the
 * old drivers/sgi/char/sgiserial.c code which itself is based of the original
 * 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 David S. Miller, Eddie C. Dost, Pete Zaitcev, Ted Ts'o and Alex Buell
 * for their work there.
 *
 *  Copyright (C) 2002 Ralf Baechle ([e-mail])
 *  Copyright (C) 2002 David S. Miller ([e-mail])
 */
#include <linux/module.h>
#include <linux/kernel.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>
#include <linux/init.h>

#include <asm/io.h>
#include <asm/irq.h>
#include <asm/sgialib.h>
#include <asm/sgi/ioc.h>
#include <asm/sgi/hpc3.h>
#include <asm/sgi/ip22.h>

#if defined(CONFIG_SERIAL_IP22_ZILOG_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
#define SUPPORT_SYSRQ
#endif

#include <linux/serial_core.h>

#include "ip22zilog.h"

/*
 * On IP22 we need to delay after register accesses but we do not need to
 * flush writes.
 */
#define ZSDELAY()		udelay(5)
#define ZSDELAY_LONG()		udelay(20)
#define ZS_WSYNC(channel)	do { } while (0)

#define NUM_IP22ZILOG		1
#define NUM_CHANNELS		(NUM_IP22ZILOG * 2)

#define ZS_CLOCK		3672000	/* 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_ip22zilog_port {
	struct uart_port		port;

	/* IRQ servicing chain.  */
	struct uart_ip22zilog_port	*next;

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

	unsigned int			flags;
#define IP22ZILOG_FLAG_IS_CONS		0x00000004
#define IP22ZILOG_FLAG_IS_KGDB		0x00000008
#define IP22ZILOG_FLAG_MODEM_STATUS	0x00000010
#define IP22ZILOG_FLAG_IS_CHANNEL_A	0x00000020
#define IP22ZILOG_FLAG_REGS_HELD	0x00000040
#define IP22ZILOG_FLAG_TX_STOPPED	0x00000080
#define IP22ZILOG_FLAG_TX_ACTIVE	0x00000100
#define IP22ZILOG_FLAG_RESET_DONE	0x00000200

	unsigned int			tty_break;

	unsigned char			parity_mask;
	unsigned char			prev_status;
};

#define ZILOG_CHANNEL_FROM_PORT(PORT)	((struct zilog_channel *)((PORT)->membase))
#define UART_ZILOG(PORT)		((struct uart_ip22zilog_port *)(PORT))
#define IP22ZILOG_GET_CURR_REG(PORT, REGNUM)		\
	(UART_ZILOG(PORT)->curregs[REGNUM])
#define IP22ZILOG_SET_CURR_REG(PORT, REGNUM, REGVAL)	\
	((UART_ZILOG(PORT)->curregs[REGNUM]) = (REGVAL))
#define ZS_IS_CONS(UP)	((UP)->flags & IP22ZILOG_FLAG_IS_CONS)
#define ZS_IS_KGDB(UP)	((UP)->flags & IP22ZILOG_FLAG_IS_KGDB)
#define ZS_WANTS_MODEM_STATUS(UP)	((UP)->flags & IP22ZILOG_FLAG_MODEM_STATUS)
#define ZS_IS_CHANNEL_A(UP)	((UP)->flags & IP22ZILOG_FLAG_IS_CHANNEL_A)
#define ZS_REGS_HELD(UP)	((UP)->flags & IP22ZILOG_FLAG_REGS_HELD)
#define ZS_TX_STOPPED(UP)	((UP)->flags & IP22ZILOG_FLAG_TX_STOPPED)
#define ZS_TX_ACTIVE(UP)	((UP)->flags & IP22ZILOG_FLAG_TX_ACTIVE)

/* Reading and writing Zilog8530 registers.  The delays are to make this
 * driver work on the IP22 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;

	writeb(reg, &channel->control);
	ZSDELAY();
	retval = readb(&channel->control);
	ZSDELAY();

	return retval;
}

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

static void ip22zilog_clear_fifo(struct zilog_channel *channel)
{
	int i;

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

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

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

		if (regval & (PAR_ERR | Rx_OVR | CRC_ERR)) {
			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);
	}

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

	ip22zilog_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 ip22zilog_maybe_update_regs(struct uart_ip22zilog_port *up,
				       struct zilog_channel *channel)
{
	if (!ZS_REGS_HELD(up)) {
		if (ZS_TX_ACTIVE(up)) {
			up->flags |= IP22ZILOG_FLAG_REGS_HELD;
		} else {
			__load_zsregs(channel, up->curregs);
		}
	}
}

#define Rx_BRK 0x0100                   /* BREAK event software flag.  */
#define Rx_SYS 0x0200                   /* SysRq event software flag.  */

static struct tty_struct *ip22zilog_receive_chars(struct uart_ip22zilog_port *up,
						  struct zilog_channel *channel)
{
	struct tty_struct *tty;
	unsigned char ch, flag;
	unsigned int r1;

	tty = NULL;
	if (up->port.info != NULL &&
	    up->port.info->tty != NULL)
		tty = up->port.info->tty;

	for (;;) {
		ch = readb(&channel->control);
		ZSDELAY();
		if (!(ch & Rx_CH_AV))
			break;

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

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

		ch &= up->parity_mask;

		/* Handle the null char got when BREAK is removed.  */
		if (!ch)
			r1 |= up->tty_break;

		/* A real serial line, record the character and status.  */
		flag = TTY_NORMAL;
		up->port.icount.rx++;
		if (r1 & (PAR_ERR | Rx_OVR | CRC_ERR | Rx_SYS | Rx_BRK)) {
			up->tty_break = 0;

			if (r1 & (Rx_SYS | Rx_BRK)) {
				up->port.icount.brk++;
				if (r1 & Rx_SYS)
					continue;
				r1 &= ~(PAR_ERR | CRC_ERR);
			}
			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 & Rx_BRK)
				flag = TTY_BREAK;
			else if (r1 & PAR_ERR)
				flag = TTY_PARITY;
			else if (r1 & CRC_ERR)
				flag = TTY_FRAME;
		}

		if (uart_handle_sysrq_char(&up->port, ch))
			continue;

		if (tty)
			uart_insert_char(&up->port, r1, Rx_OVR, ch, flag);
	}
	return tty;
}

static void ip22zilog_status_handle(struct uart_ip22zilog_port *up,
				   struct zilog_channel *channel)
{
	unsigned char status;

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

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

	if (up->curregs[R15] & BRKIE) {
		if ((status & BRK_ABRT) && !(up->prev_status & BRK_ABRT)) {
			if (uart_handle_break(&up->port))
				up->tty_break = Rx_SYS;
			else
				up->tty_break = Rx_BRK;
		}
	}

	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 ip22zilog_transmit_chars(struct uart_ip22zilog_port *up,
				    struct zilog_channel *channel)
{
	struct circ_buf *xmit;

	if (ZS_IS_CONS(up)) {
		unsigned char status = 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 &= ~IP22ZILOG_FLAG_TX_ACTIVE;

	if (ZS_REGS_HELD(up)) {
		__load_zsregs(channel, up->curregs);
		up->flags &= ~IP22ZILOG_FLAG_REGS_HELD;
	}

	if (ZS_TX_STOPPED(up)) {
		up->flags &= ~IP22ZILOG_FLAG_TX_STOPPED;
		goto ack_tx_int;
	}

	if (up->port.x_char) {
		up->flags |= IP22ZILOG_FLAG_TX_ACTIVE;
		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;