zs.c

讲述linux的初始化过程

	struct dec_serial **pp;
	int i, n, n_chips = 0, n_channels, chip, channel;

	/*
	 * did we get here by accident?
	 */
	if(!IOASIC) {
		printk("Not on JUNKIO machine, skipping probe_sccs\n");
		return;
	}
	
	/*
	 * When serial console is activated, tc_init has not been called yet
	 * and system_base is undefined. Unfortunately we have to hardcode
	 * system_base for this case :-(. HK
	 */
	switch(mips_machtype) {
	case MACH_DS5000_2X0:
		system_base = 0xbf800000;
		n_chips = 2;
		break;
	case MACH_DS5000_1XX:
		system_base = 0xbc000000;
		n_chips = 2;
		break;
	case MACH_DS5000_XX:
		system_base = 0xbc000000;
		n_chips = 1;
		break;
	}

	pp = &zs_chain;

	n_channels = 0;

	for (chip = 0; chip < n_chips; chip++) {
		for (channel = 0; channel <= 1; channel++) {
			/*
			 * The sccs reside on the high byte of the 16 bit IOBUS
			 */
			zs_channels[n_channels].control = (volatile unsigned char *)
				system_base + (0 == chip ? SCC0 : SCC1) + (0 == channel ? 1 : 9);
			zs_channels[n_channels].data = zs_channels[n_channels].control + 4;
			zs_soft[n_channels].zs_channel = &zs_channels[n_channels];
			zs_soft[n_channels].irq = SERIAL;

			if (0 == channel)
				zs_soft[n_channels].zs_chan_a = &zs_channels[n_channels+1];
			else
				zs_soft[n_channels].zs_chan_a = &zs_channels[n_channels];

			*pp = &zs_soft[n_channels];
			pp = &zs_soft[n_channels].zs_next;
			n_channels++;
		}
	}

	*pp = 0;
	zs_channels_found = n_channels;

	for (n = 0; n < zs_channels_found; n++) {
		for (i = 0; i < 16; i++) {
			zs_soft[n].zs_channel->curregs[i] = zs_init_regs[i];
		}
	}

/*	save_and_cli(flags);
	for (n = 0; n < zs_channels_found; n++) {
		if (((int)zs_channels[n].control & 0xf) == 1) {
			write_zsreg(zs_soft[channel].zs_chan_a, R9, FHWRES);
			udelay(10000);
			write_zsreg(zs_soft[channel].zs_chan_a, R9, 0);
		}
		load_zsregs(zs_soft[n].zs_channel, zs_soft[n].zs_channel->curregs);
	} 
	restore_flags(flags); */
}

/* zs_init inits the driver */
int __init zs_init(void)
{
	int channel, i;
	unsigned long flags;
	struct dec_serial *info;

	if(!IOASIC)
		return -ENODEV;

	/* Setup base handler, and timer table. */
	init_bh(SERIAL_BH, do_serial_bh);

	/* Find out how many Z8530 SCCs we have */
	if (zs_chain == 0)
		probe_sccs();

	show_serial_version();

	/* Initialize the tty_driver structure */
	/* Not all of this is exactly right for us. */

	memset(&serial_driver, 0, sizeof(struct tty_driver));
	serial_driver.magic = TTY_DRIVER_MAGIC;
	serial_driver.name = "ttyS";
	serial_driver.major = TTY_MAJOR;
	serial_driver.minor_start = 64;
	serial_driver.num = zs_channels_found;
	serial_driver.type = TTY_DRIVER_TYPE_SERIAL;
	serial_driver.subtype = SERIAL_TYPE_NORMAL;
	serial_driver.init_termios = tty_std_termios;

	serial_driver.init_termios.c_cflag =
		B9600 | CS8 | CREAD | HUPCL | CLOCAL;
	serial_driver.flags = TTY_DRIVER_REAL_RAW;
	serial_driver.refcount = &serial_refcount;
	serial_driver.table = serial_table;
	serial_driver.termios = serial_termios;
	serial_driver.termios_locked = serial_termios_locked;

	serial_driver.open = rs_open;
	serial_driver.close = rs_close;
	serial_driver.write = rs_write;
	serial_driver.flush_chars = rs_flush_chars;
	serial_driver.write_room = rs_write_room;
	serial_driver.chars_in_buffer = rs_chars_in_buffer;
	serial_driver.flush_buffer = rs_flush_buffer;
	serial_driver.ioctl = rs_ioctl;
	serial_driver.throttle = rs_throttle;
	serial_driver.unthrottle = rs_unthrottle;
	serial_driver.set_termios = rs_set_termios;
	serial_driver.stop = rs_stop;
	serial_driver.start = rs_start;
	serial_driver.hangup = rs_hangup;
	serial_driver.break_ctl = rs_break;
	serial_driver.wait_until_sent = rs_wait_until_sent;

	/*
	 * The callout device is just like normal device except for
	 * major number and the subtype code.
	 */
	callout_driver = serial_driver;
	callout_driver.name = "cua";
	callout_driver.major = TTYAUX_MAJOR;
	callout_driver.subtype = SERIAL_TYPE_CALLOUT;

	if (tty_register_driver(&serial_driver))
		panic("Couldn't register serial driver\n");
	if (tty_register_driver(&callout_driver))
		panic("Couldn't register callout driver\n");

	save_flags(flags); cli();

	for (channel = 0; channel < zs_channels_found; ++channel) {
#ifdef CONFIG_KGDB
		if (zs_soft[channel].kgdb_channel) {
			continue;
		}
#endif
		zs_soft[channel].clk_divisor = 16;
		zs_soft[channel].zs_baud = get_zsbaud(&zs_soft[channel]);

		if (request_irq(SERIAL, rs_interrupt, SA_SHIRQ,
				"SCC", &zs_soft[channel]))
			printk(KERN_ERR "decserial: can't get irq %d\n",
			       SERIAL);

		/* If console serial line, then enable interrupts. */
/*		if (zs_soft[channel].is_cons) {
			write_zsreg(zs_soft[channel].zs_channel, R1,
				    (EXT_INT_ENAB | INT_ALL_Rx | TxINT_ENAB));
			write_zsreg(zs_soft[channel].zs_channel, R9,
				    (VIS | MIE));
		}
*/
	}

	for (info = zs_chain, i = 0; info; info = info->zs_next, i++)
	{
#ifdef CONFIG_KGDB
		if (info->kgdb_channel) {
			continue;
		}
#endif
		info->magic = SERIAL_MAGIC;
		info->port = (int) info->zs_channel->control;
		info->line = i;
		info->tty = 0;
		info->custom_divisor = 16;
		info->close_delay = 50;
		info->closing_wait = 3000;
		info->x_char = 0;
		info->event = 0;
		info->count = 0;
		info->blocked_open = 0;
		info->tqueue.routine = do_softint;
		info->tqueue.data = info;
		info->callout_termios =callout_driver.init_termios;
		info->normal_termios = serial_driver.init_termios;
		init_waitqueue_head(&info->open_wait);
		init_waitqueue_head(&info->close_wait);
		printk("tty%02d at 0x%08x (irq = %d)", info->line, 
		       info->port, info->irq);
		printk(" is a Z85C30 SCC\n");
	}

	restore_flags(flags);

	return 0;
}

/*
 * register_serial and unregister_serial allows for serial ports to be
 * configured at run-time, to support PCMCIA modems.
 */
/* PowerMac: Unused at this time, just here to make things link. */
int register_serial(struct serial_struct *req)
{
	return -1;
}

void unregister_serial(int line)
{
	return;
}

/*
 * ------------------------------------------------------------
 * Serial console driver
 * ------------------------------------------------------------
 */
#ifdef CONFIG_SERIAL_CONSOLE


/*
 *	Print a string to the serial port trying not to disturb
 *	any possible real use of the port...
 */

/* This is for console output */
static void
zs_console_putchar(struct dec_serial *info, char ch)
{
	int loops = 10000;
	unsigned long flags;

	if(!info->zs_channel)
		return;

	save_flags(flags); cli();

	while (!(*(info->zs_channel->control) & Tx_BUF_EMP) && --loops)
		RECOVERY_DELAY;
	*(info->zs_channel->data) = ch;
	wbflush(); RECOVERY_DELAY;

	restore_flags(flags);
}

static void serial_console_write(struct console *co, const char *s,
				 unsigned count)
{
	struct dec_serial *info;
	int i;

	info = zs_soft + co->index;

#if 0
	/*
	 * disable master interrupt if necessary
	 */
	nine = info->zs_channel->curregs[9];
	if(nine & MIE)
		write_zsreg(info->zs_channel, R9, nine & ~MIE);
#endif
	/*
	 * do it
	 */
	for (i = 0; i < count; i++, s++) {
		if(*s == '\n')
			zs_console_putchar(info, '\r');
		zs_console_putchar(info, *s);
	}
	/*
	 * restore master interrupt enable
	 */
#if 0
	write_zsreg(info->zs_channel, R9, nine);
#endif
}

/*
 *	Receive character from the serial port
 */
static int serial_console_wait_key(struct console *co)
{
	return 0;
}

static kdev_t serial_console_device(struct console *c)
{
	return MKDEV(TTY_MAJOR, 64 + c->index);
}

/*
 *	Setup initial baud/bits/parity. We do two things here:
 *	- construct a cflag setting for the first rs_open()
 *	- initialize the serial port
 *	Return non-zero if we didn't find a serial port.
 */
static int __init serial_console_setup(struct console *co, char *options)
{
	struct dec_serial *info;
	int	baud = 9600;
	int	bits = 8;
	int	parity = 'n';
	int	cflag = CREAD | HUPCL | CLOCAL;
	char	*s;
	unsigned long flags;

	if(!IOASIC)
		return -ENODEV;

	info = zs_soft + co->index;

	if (zs_chain == 0)
		probe_sccs();

	info->is_cons = 1;

	if (options) {
		baud = simple_strtoul(options, NULL, 10);
		s = options;
		while(*s >= '0' && *s <= '9')
			s++;
		if (*s)
			parity = *s++;
		if (*s)
			bits   = *s - '0';
	}

	/*
	 *	Now construct a cflag setting.
	 */
	switch(baud) {
	case 1200:
		cflag |= B1200;
		break;
	case 2400:
		cflag |= B2400;
		break;
	case 4800:
		cflag |= B4800;
		break;
	case 19200:
		cflag |= B19200;
		break;
	case 38400:
		cflag |= B38400;
		break;
	case 57600:
		cflag |= B57600;
		break;
	case 115200:
		cflag |= B115200;
		break;
	case 9600:
	default:
		cflag |= B9600;
		break;
	}
	switch(bits) {
	case 7:
		cflag |= CS7;
		break;
	default:
	case 8:
		cflag |= CS8;
		break;
	}
	switch(parity) {
	case 'o': case 'O':
		cflag |= PARODD;
		break;
	case 'e': case 'E':
		cflag |= PARENB;
		break;
	}
	co->cflag = cflag;
#if 1 
	save_and_cli(flags);

	/*
	 * Turn on RTS and DTR.
	 */
	zs_rtsdtr(info, 1);

	/*
	 * Finally, enable sequencing
	 */
	info->zs_channel->curregs[3] |= (RxENABLE | Rx8);
	info->zs_channel->curregs[5] |= (TxENAB | Tx8);
	info->zs_channel->curregs[9] |= (VIS);
	write_zsreg(info->zs_channel, 3, info->zs_channel->curregs[3]);
	write_zsreg(info->zs_channel, 5, info->zs_channel->curregs[5]);
	write_zsreg(info->zs_channel, 9, info->zs_channel->curregs[9]);

	/*
	 * Clear the interrupt registers.
	 */
	write_zsreg(info->zs_channel, 0, ERR_RES);
	write_zsreg(info->zs_channel, 0, RES_H_IUS);

	/*
	 * Set the speed of the serial port
	 */
	change_speed(info);

	/* Save the current value of RR0 */
	info->read_reg_zero = read_zsreg(info->zs_channel, 0);

	zs_soft[co->index].clk_divisor = 16;
	zs_soft[co->index].zs_baud = get_zsbaud(&zs_soft[co->index]);

	restore_flags(flags);
#endif
	return 0;
}

static struct console sercons = {
	name:		"ttyS",
	write:		serial_console_write,
	device:		serial_console_device,
	wait_key:	serial_console_wait_key,
	setup:		serial_console_setup,
	flags:		CON_PRINTBUFFER,
	index:		-1,
};

/*
 *	Register console.
 */
void __init zs_serial_console_init(void)
{
	register_console(&sercons);
}
#endif /* ifdef CONFIG_SERIAL_CONSOLE */

#ifdef CONFIG_KGDB
/* These are for receiving and sending characters under the kgdb
 * source level kernel debugger.
 */
void putDebugChar(char kgdb_char)
{
	struct dec_zschannel *chan = zs_kgdbchan;
	while ((read_zsreg(chan, 0) & Tx_BUF_EMP) == 0)
		RECOVERY_DELAY;
	write_zsdata(chan, kgdb_char);
}
char getDebugChar(void)
{
	struct dec_zschannel *chan = zs_kgdbchan;
	while((read_zsreg(chan, 0) & Rx_CH_AV) == 0)
		eieio(); /*barrier();*/
	return read_zsdata(chan);
}
void kgdb_interruptible(int yes)
{
	struct dec_zschannel *chan = zs_kgdbchan;
	int one, nine;
	nine = read_zsreg(chan, 9);
	if (yes == 1) {
		one = EXT_INT_ENAB|INT_ALL_Rx;
		nine |= MIE;
		printk("turning serial ints on\n");
	} else {
		one = RxINT_DISAB;
		nine &= ~MIE;
		printk("turning serial ints off\n");
	}
	write_zsreg(chan, 1, one);
	write_zsreg(chan, 9, nine);
}
/* This sets up the serial port we're using, and turns on
 * interrupts for that channel, so kgdb is usable once we're done.
 */
static inline void kgdb_chaninit(struct dec_zschannel *ms, int intson, int bps)
{
	int brg;
	int i, x;
	volatile char *sccc = ms->control;
	brg = BPS_TO_BRG(bps, ZS_CLOCK/16);
	printk("setting bps on kgdb line to %d [brg=%x]\n", bps, brg);
	for (i = 20000; i != 0; --i) {
		x = *sccc; eieio();
	}
	for (i = 0; i < sizeof(scc_inittab); ++i) {
		write_zsreg(ms, scc_inittab[i], scc_inittab[i+1]);
		i++;
	}
}
/* This is called at boot time to prime the kgdb serial debugging
 * serial line.  The 'tty_num' argument is 0 for /dev/ttya and 1
 * for /dev/ttyb which is determined in setup_arch() from the
 * boot command line flags.
 */
void __init zs_kgdb_hook(int tty_num)
{
	/* Find out how many Z8530 SCCs we have */
	if (zs_chain == 0)
		probe_sccs();
	zs_soft[tty_num].zs_channel = &zs_channels[tty_num];
	zs_kgdbchan = zs_soft[tty_num].zs_channel;
	zs_soft[tty_num].change_needed = 0;
	zs_soft[tty_num].clk_divisor = 16;
	zs_soft[tty_num].zs_baud = 38400;
	zs_soft[tty_num].kgdb_channel = 1;     /* This runs kgdb */
	zs_soft[tty_num ^ 1].kgdb_channel = 0; /* This does not */
	/* Turn on transmitter/receiver at 8-bits/char */
        kgdb_chaninit(zs_soft[tty_num].zs_channel, 1, 38400);
	printk("KGDB: on channel %d initialized\n", tty_num);
	set_debug_traps(); /* init stub */
}
#endif /* ifdef CONFIG_KGDB */