uart.c

讲述linux的初始化过程

	change_speed(info);

#ifdef modem_control
	/* Handle transition to B0 status */
	if ((old_termios->c_cflag & CBAUD) &&
	    !(tty->termios->c_cflag & CBAUD)) {
		info->MCR &= ~(UART_MCR_DTR|UART_MCR_RTS);
		cli();
		serial_out(info, UART_MCR, info->MCR);
		sti();
	}
	
	/* Handle transition away from B0 status */
	if (!(old_termios->c_cflag & CBAUD) &&
	    (tty->termios->c_cflag & CBAUD)) {
		info->MCR |= UART_MCR_DTR;
		if (!tty->hw_stopped ||
		    !(tty->termios->c_cflag & CRTSCTS)) {
			info->MCR |= UART_MCR_RTS;
		}
		cli();
		serial_out(info, UART_MCR, info->MCR);
		sti();
	}
	
	/* Handle turning off CRTSCTS */
	if ((old_termios->c_cflag & CRTSCTS) &&
	    !(tty->termios->c_cflag & CRTSCTS)) {
		tty->hw_stopped = 0;
		rs_8xx_start(tty);
	}
#endif

#if 0
	/*
	 * No need to wake up processes in open wait, since they
	 * sample the CLOCAL flag once, and don't recheck it.
	 * XXX  It's not clear whether the current behavior is correct
	 * or not.  Hence, this may change.....
	 */
	if (!(old_termios->c_cflag & CLOCAL) &&
	    (tty->termios->c_cflag & CLOCAL))
		wake_up_interruptible(&info->open_wait);
#endif
}

/*
 * ------------------------------------------------------------
 * rs_close()
 * 
 * This routine is called when the serial port gets closed.  First, we
 * wait for the last remaining data to be sent.  Then, we unlink its
 * async structure from the interrupt chain if necessary, and we free
 * that IRQ if nothing is left in the chain.
 * ------------------------------------------------------------
 */
static void rs_8xx_close(struct tty_struct *tty, struct file * filp)
{
	ser_info_t *info = (ser_info_t *)tty->driver_data;
	struct serial_state *state;
	unsigned long	flags;
	int		idx;
	volatile smc_t	*smcp;
	volatile scc_t	*sccp;

	if (!info || serial_paranoia_check(info, tty->device, "rs_close"))
		return;

	state = info->state;
	
	save_flags(flags); cli();
	
	if (tty_hung_up_p(filp)) {
		DBG_CNT("before DEC-hung");
		MOD_DEC_USE_COUNT;
		restore_flags(flags);
		return;
	}
	
#ifdef SERIAL_DEBUG_OPEN
	printk("rs_close ttys%d, count = %d\n", info->line, state->count);
#endif
	if ((tty->count == 1) && (state->count != 1)) {
		/*
		 * Uh, oh.  tty->count is 1, which means that the tty
		 * structure will be freed.  state->count should always
		 * be one in these conditions.  If it's greater than
		 * one, we've got real problems, since it means the
		 * serial port won't be shutdown.
		 */
		printk("rs_close: bad serial port count; tty->count is 1, "
		       "state->count is %d\n", state->count);
		state->count = 1;
	}
	if (--state->count < 0) {
		printk("rs_close: bad serial port count for ttys%d: %d\n",
		       info->line, state->count);
		state->count = 0;
	}
	if (state->count) {
		DBG_CNT("before DEC-2");
		MOD_DEC_USE_COUNT;
		restore_flags(flags);
		return;
	}
	info->flags |= ASYNC_CLOSING;
	/*
	 * Save the termios structure, since this port may have
	 * separate termios for callout and dialin.
	 */
	if (info->flags & ASYNC_NORMAL_ACTIVE)
		info->state->normal_termios = *tty->termios;
	if (info->flags & ASYNC_CALLOUT_ACTIVE)
		info->state->callout_termios = *tty->termios;
	/*
	 * Now we wait for the transmit buffer to clear; and we notify 
	 * the line discipline to only process XON/XOFF characters.
	 */
	tty->closing = 1;
	if (info->closing_wait != ASYNC_CLOSING_WAIT_NONE)
		tty_wait_until_sent(tty, info->closing_wait);
	/*
	 * At this point we stop accepting input.  To do this, we
	 * disable the receive line status interrupts, and tell the
	 * interrupt driver to stop checking the data ready bit in the
	 * line status register.
	 */
	info->read_status_mask &= ~BD_SC_EMPTY;
	if (info->flags & ASYNC_INITIALIZED) {
		if ((idx = info->state->smc_scc_num) < SCC_NUM_BASE) {
			smcp = &immr->im_smc[idx];
			smcp->smc_smcm &= ~SMCM_RX;
			smcp->smc_smcmr &= ~SMCMR_REN;
		}
		else {
			sccp = &immr->im_scc[idx - SCC_IDX_BASE];
			sccp->scc_sccm &= ~UART_SCCM_RX;
			sccp->scc_gsmrl &= ~SCC_GSMRL_ENR;
		}
		/*
		 * Before we drop DTR, make sure the UART transmitter
		 * has completely drained; this is especially
		 * important if there is a transmit FIFO!
		 */
		rs_8xx_wait_until_sent(tty, info->timeout);
	}
	shutdown(info);
	if (tty->driver.flush_buffer)
		tty->driver.flush_buffer(tty);
	if (tty->ldisc.flush_buffer)
		tty->ldisc.flush_buffer(tty);
	tty->closing = 0;
	info->event = 0;
	info->tty = 0;
	if (info->blocked_open) {
		if (info->close_delay) {
			current->state = TASK_INTERRUPTIBLE;
			schedule_timeout(info->close_delay);
		}
		wake_up_interruptible(&info->open_wait);
	}
	info->flags &= ~(ASYNC_NORMAL_ACTIVE|ASYNC_CALLOUT_ACTIVE|
			 ASYNC_CLOSING);
	wake_up_interruptible(&info->close_wait);
	MOD_DEC_USE_COUNT;
	restore_flags(flags);
}

/*
 * rs_wait_until_sent() --- wait until the transmitter is empty
 */
static void rs_8xx_wait_until_sent(struct tty_struct *tty, int timeout)
{
	ser_info_t *info = (ser_info_t *)tty->driver_data;
	unsigned long orig_jiffies, char_time;
	/*int lsr;*/
	volatile cbd_t *bdp;
	
	if (serial_paranoia_check(info, tty->device, "rs_wait_until_sent"))
		return;

#ifdef maybe
	if (info->state->type == PORT_UNKNOWN)
		return;
#endif

	orig_jiffies = jiffies;
	/*
	 * Set the check interval to be 1/5 of the estimated time to
	 * send a single character, and make it at least 1.  The check
	 * interval should also be less than the timeout.
	 * 
	 * Note: we have to use pretty tight timings here to satisfy
	 * the NIST-PCTS.
	 */
	char_time = 1;
	if (timeout)
		char_time = MIN(char_time, timeout);
#ifdef SERIAL_DEBUG_RS_WAIT_UNTIL_SENT
	printk("In rs_wait_until_sent(%d) check=%lu...", timeout, char_time);
	printk("jiff=%lu...", jiffies);
#endif

	/* We go through the loop at least once because we can't tell
	 * exactly when the last character exits the shifter.  There can
	 * be at least two characters waiting to be sent after the buffers
	 * are empty.
	 */
	do {
#ifdef SERIAL_DEBUG_RS_WAIT_UNTIL_SENT
		printk("lsr = %d (jiff=%lu)...", lsr, jiffies);
#endif
		current->state = TASK_INTERRUPTIBLE;
/*		current->counter = 0;	 make us low-priority */
		schedule_timeout(char_time);
		if (signal_pending(current))
			break;
		if (timeout && ((orig_jiffies + timeout) < jiffies))
			break;
		bdp = info->tx_cur;
	} while (bdp->cbd_sc & BD_SC_READY);
	current->state = TASK_RUNNING;
#ifdef SERIAL_DEBUG_RS_WAIT_UNTIL_SENT
	printk("lsr = %d (jiff=%lu)...done\n", lsr, jiffies);
#endif
}

/*
 * rs_hangup() --- called by tty_hangup() when a hangup is signaled.
 */
static void rs_8xx_hangup(struct tty_struct *tty)
{
	ser_info_t *info = (ser_info_t *)tty->driver_data;
	struct serial_state *state = info->state;
	
	if (serial_paranoia_check(info, tty->device, "rs_hangup"))
		return;

	state = info->state;
	
	rs_8xx_flush_buffer(tty);
	shutdown(info);
	info->event = 0;
	state->count = 0;
	info->flags &= ~(ASYNC_NORMAL_ACTIVE|ASYNC_CALLOUT_ACTIVE);
	info->tty = 0;
	wake_up_interruptible(&info->open_wait);
}

/*
 * ------------------------------------------------------------
 * rs_open() and friends
 * ------------------------------------------------------------
 */
static int block_til_ready(struct tty_struct *tty, struct file * filp,
			   ser_info_t *info)
{
#ifdef DO_THIS_LATER
	DECLARE_WAITQUEUE(wait, current);
#endif
	struct serial_state *state = info->state;
	int		retval;
	int		do_clocal = 0;

	/*
	 * If the device is in the middle of being closed, then block
	 * until it's done, and then try again.
	 */
	if (tty_hung_up_p(filp) ||
	    (info->flags & ASYNC_CLOSING)) {
		if (info->flags & ASYNC_CLOSING)
			interruptible_sleep_on(&info->close_wait);
#ifdef SERIAL_DO_RESTART
		if (info->flags & ASYNC_HUP_NOTIFY)
			return -EAGAIN;
		else
			return -ERESTARTSYS;
#else
		return -EAGAIN;
#endif
	}

	/*
	 * If this is a callout device, then just make sure the normal
	 * device isn't being used.
	 */
	if (tty->driver.subtype == SERIAL_TYPE_CALLOUT) {
		if (info->flags & ASYNC_NORMAL_ACTIVE)
			return -EBUSY;
		if ((info->flags & ASYNC_CALLOUT_ACTIVE) &&
		    (info->flags & ASYNC_SESSION_LOCKOUT) &&
		    (info->session != current->session))
		    return -EBUSY;
		if ((info->flags & ASYNC_CALLOUT_ACTIVE) &&
		    (info->flags & ASYNC_PGRP_LOCKOUT) &&
		    (info->pgrp != current->pgrp))
		    return -EBUSY;
		info->flags |= ASYNC_CALLOUT_ACTIVE;
		return 0;
	}
	
	/*
	 * If non-blocking mode is set, or the port is not enabled,
	 * then make the check up front and then exit.
	 * If this is an SMC port, we don't have modem control to wait
	 * for, so just get out here.
	 */
	if ((filp->f_flags & O_NONBLOCK) ||
	    (tty->flags & (1 << TTY_IO_ERROR)) ||
	    (info->state->smc_scc_num < SCC_NUM_BASE)) {
		if (info->flags & ASYNC_CALLOUT_ACTIVE)
			return -EBUSY;
		info->flags |= ASYNC_NORMAL_ACTIVE;
		return 0;
	}

	if (info->flags & ASYNC_CALLOUT_ACTIVE) {
		if (state->normal_termios.c_cflag & CLOCAL)
			do_clocal = 1;
	} else {
		if (tty->termios->c_cflag & CLOCAL)
			do_clocal = 1;
	}
	
	/*
	 * Block waiting for the carrier detect and the line to become
	 * free (i.e., not in use by the callout).  While we are in
	 * this loop, state->count is dropped by one, so that
	 * rs_close() knows when to free things.  We restore it upon
	 * exit, either normal or abnormal.
	 */
	retval = 0;
#ifdef DO_THIS_LATER
	add_wait_queue(&info->open_wait, &wait);
#ifdef SERIAL_DEBUG_OPEN
	printk("block_til_ready before block: ttys%d, count = %d\n",
	       state->line, state->count);
#endif
	cli();
	if (!tty_hung_up_p(filp)) 
		state->count--;
	sti();
	info->blocked_open++;
	while (1) {
		cli();
		if (!(info->flags & ASYNC_CALLOUT_ACTIVE) &&
		    (tty->termios->c_cflag & CBAUD))
			serial_out(info, UART_MCR,
				   serial_inp(info, UART_MCR) |
				   (UART_MCR_DTR | UART_MCR_RTS));
		sti();
		set_current_state(TASK_INTERRUPTIBLE);
		if (tty_hung_up_p(filp) ||
		    !(info->flags & ASYNC_INITIALIZED)) {
#ifdef SERIAL_DO_RESTART
			if (info->flags & ASYNC_HUP_NOTIFY)
				retval = -EAGAIN;
			else
				retval = -ERESTARTSYS;	
#else
			retval = -EAGAIN;
#endif
			break;
		}
		if (!(info->flags & ASYNC_CALLOUT_ACTIVE) &&
		    !(info->flags & ASYNC_CLOSING) &&
		    (do_clocal || (serial_in(info, UART_MSR) &
				   UART_MSR_DCD)))
			break;
		if (signal_pending(current)) {
			retval = -ERESTARTSYS;
			break;
		}
#ifdef SERIAL_DEBUG_OPEN
		printk("block_til_ready blocking: ttys%d, count = %d\n",
		       info->line, state->count);
#endif
		schedule();
	}
	current->state = TASK_RUNNING;
	remove_wait_queue(&info->open_wait, &wait);
	if (!tty_hung_up_p(filp))
		state->count++;
	info->blocked_open--;
#ifdef SERIAL_DEBUG_OPEN
	printk("block_til_ready after blocking: ttys%d, count = %d\n",
	       info->line, state->count);
#endif
#endif /* DO_THIS_LATER */
	if (retval)
		return retval;
	info->flags |= ASYNC_NORMAL_ACTIVE;
	return 0;
}

static int get_async_struct(int line, ser_info_t **ret_info)
{
	struct serial_state *sstate;

	sstate = rs_table + line;
	if (sstate->info) {
		sstate->count++;
		*ret_info = (ser_info_t *)sstate->info;
		return 0;
	}
	else {
		return -ENOMEM;
	}
}

/*
 * This routine is called whenever a serial port is opened.  It
 * enables interrupts for a serial port, linking in its async structure into
 * the IRQ chain.   It also performs the serial-specific
 * initialization for the tty structure.
 */
static int rs_8xx_open(struct tty_struct *tty, struct file * filp)
{
	ser_info_t	*info;
	int 		retval, line;

	line = MINOR(tty->device) - tty->driver.minor_start;
	if ((line < 0) || (line >= NR_PORTS))
		return -ENODEV;
	retval = get_async_struct(line, &info);
	if (retval)
		return retval;
	if (serial_paranoia_check(info, tty->device, "rs_open"))
		return -ENODEV;

#ifdef SERIAL_DEBUG_OPEN
	printk("rs_open %s%d, count = %d\n", tty->driver.name, info->line,
	       info->state->count);
#endif
	tty->driver_data = info;
	info->tty = tty;

	/*
	 * Start up serial port
	 */
	retval = startup(info);
	if (retval)
		return retval;

	MOD_INC_USE_COUNT;
	retval = block_til_ready(tty, filp, info);
	if (retval) {
#ifdef SERIAL_DEBUG_OPEN
		printk("rs_open returning after block_til_ready with %d\n",
		       retval);
#endif
		return retval;
	}

	if ((info->state->count == 1) &&
	    (info->flags & ASYNC_SPLIT_TERMIOS)) {
		if (tty->driver.subtype == SERIAL_TYPE_NORMAL)
			*tty->termios = info->state->normal_termios;
		else 
			*tty->termios = info->state->callout_termios;
		change_speed(info);
	}

	info->session = current->session;
	info->pgrp = current->pgrp;

#ifdef SERIAL_DEBUG_OPEN
	printk("rs_open ttys%d successful...", info->line);
#endif
	return 0;
}

/*
 * /proc fs routines....
 */

static int inline line_info(char *buf, struct serial_state *state)
{
#ifdef notdef
	struct async_struct *info = state->info, scr_info;
	char	stat_buf[30], control, status;
#endif
	int	ret;

	ret = sprintf(buf, "%d: uart:%s port:%X irq:%d",
		      state->line,
		      (state->smc_scc_num < SCC_NUM_BASE) ? "SMC" : "SCC",
		      state->port, state->irq);

	if (!state->port || (state->type == PORT_UNKNOWN)) {
		ret += sprintf(buf+ret, "\n");
		return ret;
	}

#ifdef notdef
	/*
	 * Figure out the current RS-232 lines
	 */
	if (!info) {
		info = &scr_info;	/* This is just for serial_{in,out} */

		info->magic = SERIAL_MAGIC;
		info->port = state->port;
		info->flags = state->flags;
		info->quot = 0;
		info->tty = 0;