8250.c

linux 2.6内核下8250串口设备驱动程序

	else
		serial_outp(up, UART_IER, 0);

 out:	
	spin_unlock_irqrestore(&up->port.lock, flags);
//	restore_flags(flags);
	DEBUG_AUTOCONF("type=%s\n", uart_config[up->port.type].name);
}

static void autoconfig_irq(struct uart_8250_port *up)
{
	unsigned char save_mcr, save_ier;
	unsigned char save_ICP = 0;
	unsigned int ICP = 0;
	unsigned long irqs;
	int irq;

	if (up->port.flags & UPF_FOURPORT) {
		ICP = (up->port.iobase & 0xfe0) | 0x1f;
		save_ICP = inb_p(ICP);
		outb_p(0x80, ICP);
		(void) inb_p(ICP);
	}

	/* forget possible initially masked and pending IRQ */
	probe_irq_off(probe_irq_on());
	save_mcr = serial_inp(up, UART_MCR);
	save_ier = serial_inp(up, UART_IER);
	serial_outp(up, UART_MCR, UART_MCR_OUT1 | UART_MCR_OUT2);
	
	irqs = probe_irq_on();
	serial_outp(up, UART_MCR, 0);
	udelay (10);
	if (up->port.flags & UPF_FOURPORT)  {
		serial_outp(up, UART_MCR,
			    UART_MCR_DTR | UART_MCR_RTS);
	} else {
		serial_outp(up, UART_MCR,
			    UART_MCR_DTR | UART_MCR_RTS | UART_MCR_OUT2);
	}
	serial_outp(up, UART_IER, 0x0f);	/* enable all intrs */
	(void)serial_inp(up, UART_LSR);
	(void)serial_inp(up, UART_RX);
	(void)serial_inp(up, UART_IIR);
	(void)serial_inp(up, UART_MSR);
	serial_outp(up, UART_TX, 0xFF);
	udelay (20);
	irq = probe_irq_off(irqs);

	serial_outp(up, UART_MCR, save_mcr);
	serial_outp(up, UART_IER, save_ier);

	if (up->port.flags & UPF_FOURPORT)
		outb_p(save_ICP, ICP);

	up->port.irq = (irq > 0) ? irq : 0;
}

static inline void __stop_tx(struct uart_8250_port *p)
{
	if (p->ier & UART_IER_THRI) {
		p->ier &= ~UART_IER_THRI;
		serial_out(p, UART_IER, p->ier);
	}
}

static void serial8250_stop_tx(struct uart_port *port)
{
	struct uart_8250_port *up = (struct uart_8250_port *)port;

	__stop_tx(up);

	/*
	 * We really want to stop the transmitter from sending.
	 */
	if (up->port.type == PORT_16C950) {
		up->acr |= UART_ACR_TXDIS;
		serial_icr_write(up, UART_ACR, up->acr);
	}
}

static void transmit_chars(struct uart_8250_port *up);

static void serial8250_start_tx(struct uart_port *port)
{
	struct uart_8250_port *up = (struct uart_8250_port *)port;

	if (!(up->ier & UART_IER_THRI)) {
		up->ier |= UART_IER_THRI;
		serial_out(up, UART_IER, up->ier);

		if (up->bugs & UART_BUG_TXEN) {
			unsigned char lsr, iir;
			lsr = serial_in(up, UART_LSR);
			iir = serial_in(up, UART_IIR);
			if (lsr & UART_LSR_TEMT && iir & UART_IIR_NO_INT)
				transmit_chars(up);
		}
	}

	/*
	 * Re-enable the transmitter if we disabled it.
	 */
	if (up->port.type == PORT_16C950 && up->acr & UART_ACR_TXDIS) {
		up->acr &= ~UART_ACR_TXDIS;
		serial_icr_write(up, UART_ACR, up->acr);
	}
}

static void serial8250_stop_rx(struct uart_port *port)
{
	struct uart_8250_port *up = (struct uart_8250_port *)port;

	up->ier &= ~UART_IER_RLSI;
	up->port.read_status_mask &= ~UART_LSR_DR;
	serial_out(up, UART_IER, up->ier);
}

static void serial8250_enable_ms(struct uart_port *port)
{
	struct uart_8250_port *up = (struct uart_8250_port *)port;

	/* no MSR capabilities */
	if (up->bugs & UART_BUG_NOMSR)
		return;

	up->ier |= UART_IER_MSI;
	serial_out(up, UART_IER, up->ier);
}

static void
receive_chars(struct uart_8250_port *up, int *status)
{
	struct tty_struct *tty = up->port.info->tty;
	unsigned char ch, lsr = *status;
	int max_count = 256;
	char flag;

	do {
		ch = serial_inp(up, UART_RX);
		flag = TTY_NORMAL;
		up->port.icount.rx++;

#ifdef CONFIG_SERIAL_8250_CONSOLE
		/*
		 * Recover the break flag from console xmit
		 */
		if (up->port.line == up->port.cons->index) {
			lsr |= up->lsr_break_flag;
			up->lsr_break_flag = 0;
		}
#endif

		if (unlikely(lsr & (UART_LSR_BI | UART_LSR_PE |
				    UART_LSR_FE | UART_LSR_OE))) {
			/*
			 * For statistics only
			 */
			if (lsr & UART_LSR_BI) {
				lsr &= ~(UART_LSR_FE | UART_LSR_PE);
				up->port.icount.brk++;
				/*
				 * We do the SysRQ and SAK checking
				 * here because otherwise the break
				 * may get masked by ignore_status_mask
				 * or read_status_mask.
				 */
				if (uart_handle_break(&up->port))
					goto ignore_char;
			} else if (lsr & UART_LSR_PE)
				up->port.icount.parity++;
			else if (lsr & UART_LSR_FE)
				up->port.icount.frame++;
			if (lsr & UART_LSR_OE)
				up->port.icount.overrun++;

			/*
			 * Mask off conditions which should be ignored.
			 */
			lsr &= up->port.read_status_mask;

			if (lsr & UART_LSR_BI) {
				DEBUG_INTR("handling break....");
				flag = TTY_BREAK;
			} else if (lsr & UART_LSR_PE)
				flag = TTY_PARITY;
			else if (lsr & UART_LSR_FE)
				flag = TTY_FRAME;
		}
		if (uart_handle_sysrq_char(&up->port, ch))
			goto ignore_char;

		uart_insert_char(&up->port, lsr, UART_LSR_OE, ch, flag);

	ignore_char:
		lsr = serial_inp(up, UART_LSR);
	} while ((lsr & UART_LSR_DR) && (max_count-- > 0));
	spin_unlock(&up->port.lock);
	tty_flip_buffer_push(tty);
	spin_lock(&up->port.lock);
	*status = lsr;
}

static void transmit_chars(struct uart_8250_port *up)
{
	struct circ_buf *xmit = &up->port.info->xmit;
	int count;

	if (up->port.x_char) {
		serial_outp(up, UART_TX, up->port.x_char);
		up->port.icount.tx++;
		up->port.x_char = 0;
		return;
	}
	if (uart_tx_stopped(&up->port)) {
		serial8250_stop_tx(&up->port);
		return;
	}
	if (uart_circ_empty(xmit)) {
		__stop_tx(up);
		return;
	}

	count = up->tx_loadsz;
	do {
		serial_out(up, UART_TX, xmit->buf[xmit->tail]);
		xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
		up->port.icount.tx++;
		if (uart_circ_empty(xmit))
			break;
	} while (--count > 0);

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

	DEBUG_INTR("THRE...");

	if (uart_circ_empty(xmit))
		__stop_tx(up);
}

static unsigned int check_modem_status(struct uart_8250_port *up)
{
	unsigned int status = serial_in(up, UART_MSR);

	if (status & UART_MSR_ANY_DELTA && up->ier & UART_IER_MSI) {
		if (status & UART_MSR_TERI)
			up->port.icount.rng++;
		if (status & UART_MSR_DDSR)
			up->port.icount.dsr++;
		if (status & UART_MSR_DDCD)
			uart_handle_dcd_change(&up->port, status & UART_MSR_DCD);
		if (status & UART_MSR_DCTS)
			uart_handle_cts_change(&up->port, status & UART_MSR_CTS);

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

	return status;
}

/*
 * This handles the interrupt from one port.
 */
static inline void
serial8250_handle_port(struct uart_8250_port *up)
{
	unsigned int status;

	spin_lock(&up->port.lock);

	status = serial_inp(up, UART_LSR);

	DEBUG_INTR("status = %x...", status);

	if (status & UART_LSR_DR)
		receive_chars(up, &status);
	check_modem_status(up);
	if (status & UART_LSR_THRE)
		transmit_chars(up);

	spin_unlock(&up->port.lock);
}

/*
 * This is the serial driver's interrupt routine.
 *
 * Arjan thinks the old way was overly complex, so it got simplified.
 * Alan disagrees, saying that need the complexity to handle the weird
 * nature of ISA shared interrupts.  (This is a special exception.)
 *
 * In order to handle ISA shared interrupts properly, we need to check
 * that all ports have been serviced, and therefore the ISA interrupt
 * line has been de-asserted.
 *
 * This means we need to loop through all ports. checking that they
 * don't have an interrupt pending.
 */
static irqreturn_t serial8250_interrupt(int irq, void *dev_id)
{
	struct irq_info *i = dev_id;
	struct list_head *l, *end = NULL;
	int pass_counter = 0, handled = 0;

	DEBUG_INTR("serial8250_interrupt(%d)...", irq);

	spin_lock(&i->lock);

	l = i->head;
	do {
		struct uart_8250_port *up;
		unsigned int iir;

		up = list_entry(l, struct uart_8250_port, list);

		iir = serial_in(up, UART_IIR);
		if (!(iir & UART_IIR_NO_INT)) {
			serial8250_handle_port(up);

			handled = 1;

			end = NULL;
		} else if (end == NULL)
			end = l;

		l = l->next;

		if (l == i->head && pass_counter++ > PASS_LIMIT) {
			/* If we hit this, we're dead. */
			printk(KERN_ERR "serial8250: too much work for "
				"irq%d\n", irq);
			break;
		}
	} while (l != end);

	spin_unlock(&i->lock);

	DEBUG_INTR("end.\n");

	return IRQ_RETVAL(handled);
}

/*
 * To support ISA shared interrupts, we need to have one interrupt
 * handler that ensures that the IRQ line has been deasserted
 * before returning.  Failing to do this will result in the IRQ
 * line being stuck active, and, since ISA irqs are edge triggered,
 * no more IRQs will be seen.
 */
static void serial_do_unlink(struct irq_info *i, struct uart_8250_port *up)
{
	spin_lock_irq(&i->lock);

	if (!list_empty(i->head)) {
		if (i->head == &up->list)
			i->head = i->head->next;
		list_del(&up->list);
	} else {
		BUG_ON(i->head != &up->list);
		i->head = NULL;
	}

	spin_unlock_irq(&i->lock);
}

static int serial_link_irq_chain(struct uart_8250_port *up)
{
	struct irq_info *i = irq_lists + up->port.irq;
	int ret, irq_flags = up->port.flags & UPF_SHARE_IRQ ? IRQF_SHARED : 0;

	spin_lock_irq(&i->lock);

	if (i->head) {
		list_add(&up->list, i->head);
		spin_unlock_irq(&i->lock);

		ret = 0;
	} else {
		INIT_LIST_HEAD(&up->list);
		i->head = &up->list;
		spin_unlock_irq(&i->lock);

		ret = request_irq(up->port.irq, serial8250_interrupt,
				  irq_flags, "serial", i);
		if (ret < 0)
			serial_do_unlink(i, up);
	}

	return ret;
}

static void serial_unlink_irq_chain(struct uart_8250_port *up)
{
	struct irq_info *i = irq_lists + up->port.irq;

	BUG_ON(i->head == NULL);

	if (list_empty(i->head))
		free_irq(up->port.irq, i);

	serial_do_unlink(i, up);
}

/*
 * This function is used to handle ports that do not have an
 * interrupt.  This doesn't work very well for 16450's, but gives
 * barely passable results for a 16550A.  (Although at the expense
 * of much CPU overhead).
 */
static void serial8250_timeout(unsigned long data)
{
	struct uart_8250_port *up = (struct uart_8250_port *)data;
	unsigned int timeout;
	unsigned int iir;

	iir = serial_in(up, UART_IIR);
	if (!(iir & UART_IIR_NO_INT))
		serial8250_handle_port(up);

	timeout = up->port.timeout;
	timeout = timeout > 6 ? (timeout / 2 - 2) : 1;
	mod_timer(&up->timer, jiffies + timeout);
}

static unsigned int serial8250_tx_empty(struct uart_port *port)
{
	struct uart_8250_port *up = (struct uart_8250_port *)port;
	unsigned long flags;
	unsigned int ret;

	spin_lock_irqsave(&up->port.lock, flags);
	ret = serial_in(up, UART_LSR) & UART_LSR_TEMT ? TIOCSER_TEMT : 0;
	spin_unlock_irqrestore(&up->port.lock, flags);

	return ret;
}

static unsigned int serial8250_get_mctrl(struct uart_port *port)
{
	struct uart_8250_port *up = (struct uart_8250_port *)port;
	unsigned int status;
	unsigned int ret;

	status = check_modem_status(up);

	ret = 0;
	if (status & UART_MSR_DCD)
		ret |= TIOCM_CAR;
	if (status & UART_MSR_RI)
		ret |= TIOCM_RNG;
	if (status & UART_MSR_DSR)
		ret |= TIOCM_DSR;
	if (status & UART_MSR_CTS)
		ret |= TIOCM_CTS;
	return ret;
}

static void serial8250_set_mctrl(struct uart_port *port, unsigned int mctrl)
{
	struct uart_8250_port *up = (struct uart_8250_port *)port;
	unsigned char mcr = 0;

	if (mctrl & TIOCM_RTS)
		mcr |= UART_MCR_RTS;
	if (mctrl & TIOCM_DTR)
		mcr |= UART_MCR_DTR;
	if (mctrl & TIOCM_OUT1)
		mcr |= UART_MCR_OUT1;
	if (mctrl & TIOCM_OUT2)
		mcr |= UART_MCR_OUT2;
	if (mctrl & TIOCM_LOOP)
		mcr |= UART_MCR_LOOP;

	mcr = (mcr & up->mcr_mask) | up->mcr_force | up->mcr;

	serial_out(up, UART_MCR, mcr);
}

static void serial8250_break_ctl(struct uart_port *port, int break_state)
{
	struct uart_8250_port *up = (struct uart_8250_port *)port;
	unsigned long flags;

	spin_lock_irqsave(&up->port.lock, flags);
	if (break_state == -1)
		up->lcr |= UART_LCR_SBC;
	else
		up->lcr &= ~UART_LCR_SBC;
	serial_out(up, UART_LCR, up->lcr);
	spin_unlock_irqrestore(&up->port.lock, flags);
}

static int serial8250_startup(struct uart_port *port)
{
	struct uart_8250_port *up = (struct uart_8250_port *)port;
	unsigned long flags;
	unsigned char lsr, iir;
	int retval;

	up->capabilities = uart_config[up->port.type].flags;
	up->mcr = 0;

	if (up->port.type == PORT_16C950) {
		/* Wake up and initialize UART */
		up->acr = 0;
		serial_outp(up, UART_LCR, 0xBF);
		serial_outp(up, UART_EFR, UART_EFR_ECB);
		serial_outp(up, UART_IER, 0);
		serial_outp(up, UART_LCR, 0);
		serial_icr_write(up, UART_CSR, 0); /* Reset the UART */
		serial_outp(up, UART_LCR, 0xBF);
		serial_outp(up, UART_EFR, UART_EFR_ECB);
		serial_outp(up, UART_LCR, 0);
	}

#ifdef CONFIG_SERIAL_8250_RSA
	/*
	 * If this is an RSA port, see if we can kick it up to the
	 * higher speed clock.
	 */
	enable_rsa(up);
#endif