serial.c

这个linux源代码是很全面的~基本完整了~使用c编译的~由于时间问题我没有亲自测试~但就算用来做参考资料也是非常好的

	
	for (i = 0; i < NR_PORTS; i++) {
		info = rs_table + i;
		if (!info->enabled || !info->uses_dma) 
			continue; 
		/* check for dma_descr (don't need to check for dma_eop in output dma for serial */
		if (ireg & info->irq) {  
			/* we can send a new dma bunch. make it so. */
			DEBUG_LOG(info->line, "tr_interrupt %i\n", i);
			/* Read jiffies_usec first, 
			 * we want this time to be as late as possible
			 */
 			PROCSTAT(ser_stat[info->line].tx_dma_ints++);
			info->last_tx_active_usec = GET_JIFFIES_USEC();
			info->last_tx_active = jiffies;
			transmit_chars(info);
		}
		
		/* FIXME: here we should really check for a change in the
		   status lines and if so call status_handle(info) */
	}
}

/* dma input channel interrupt handler */

static void 
rec_interrupt(int irq, void *dev_id, struct pt_regs * regs)
{
	struct e100_serial *info;
	unsigned long ireg;
	int i;

#ifdef CONFIG_SVINTO_SIM
	/* No receive in the simulator.  Will probably be when the rest of
	 * the serial interface works, and this piece will just be removed.
	 */
	{
		const char *s = "What? rec_interrupt in simulator??\n";
		SIMCOUT(s,strlen(s));
	}
	return;
#endif
	
	/* find out the line that caused this irq and get it from rs_table */
	
	ireg = *R_IRQ_MASK2_RD;  /* get the active irq bits for the dma channels */
	
	for (i = 0; i < NR_PORTS; i++) {
		info = rs_table + i;
		if (!info->enabled || !info->uses_dma) 
			continue; 
		/* check for both dma_eop and dma_descr for the input dma channel */
		if (ireg & ((info->irq << 2) | (info->irq << 3))) {
			/* we have received something */
			receive_chars(info);
		}
		
		/* FIXME: here we should really check for a change in the
		   status lines and if so call status_handle(info) */
	}
}

static _INLINE_ int
force_eop_if_needed(struct e100_serial *info)
{
	/* We check data_avail bit to determine if data has 
	 * arrived since last time
	 */ 
	unsigned char rstat = info->port[REG_STATUS];

	/* error or datavail? */
	if (rstat & SER_ERROR_MASK) { 
		/* Some error has occurred. If there has been valid data, an
		 * EOP interrupt will be made automatically. If no data, the
		 * normal ser_interrupt should be enabled and handle it.
		 * So do nothing!
		 */
		DEBUG_LOG(info->line, "timeout err: rstat 0x%03X\n",
		          rstat | (info->line << 8));
		return 0;
	}

	if (rstat & SER_DATA_AVAIL_MASK) { 
		/* Ok data, no error, count it */
		TIMERD(DEBUG_LOG(info->line, "timeout: rstat 0x%03X\n",
		          rstat | (info->line << 8)));
		/* Read data to clear status flags */
		(void)info->port[REG_DATA];

		info->forced_eop = 0;
		START_FLUSH_FAST_TIMER(info, "magic");
		return 0;
	}

	/* hit the timeout, force an EOP for the input
	 * dma channel if we haven't already
	 */
	if (!info->forced_eop) {
		info->forced_eop = 1;
		PROCSTAT(ser_stat[info->line].timeout_flush_cnt++);
		DEBUG_LOG(info->line, "timeout EOP %i\n", info->line);
		FORCE_EOP(info);
	}

	return 1;
}

extern _INLINE_ void
flush_to_flip_buffer(struct e100_serial *info)
{
	struct tty_struct *tty;
	struct etrax_recv_buffer *buffer;
	unsigned int length;
	unsigned long flags;

	if (!info->first_recv_buffer)
		return;

	save_flags(flags);
	cli();

	if (!(tty = info->tty)) {
		restore_flags(flags);
		return;
	}

	length = tty->flip.count;

	while ((buffer = info->first_recv_buffer) && length < TTY_FLIPBUF_SIZE) {
		unsigned int count = buffer->length;

		if (length + count > TTY_FLIPBUF_SIZE)
			count = TTY_FLIPBUF_SIZE - length;

		memcpy(tty->flip.char_buf_ptr + length, buffer->buffer, count);
		memset(tty->flip.flag_buf_ptr + length, TTY_NORMAL, count);
		tty->flip.flag_buf_ptr[length] = buffer->error;

		length += count;
		info->recv_cnt -= count;

		if (count == buffer->length) {
			info->first_recv_buffer = buffer->next;
			kfree(buffer);
		} else {
			buffer->length -= count;
			memmove(buffer->buffer, buffer->buffer + count, buffer->length);
			buffer->error = TTY_NORMAL;
		}
	}

	if (!info->first_recv_buffer)
		info->last_recv_buffer = NULL;

	tty->flip.count = length;

	restore_flags(flags);

#if LINUX_VERSION_CODE > KERNEL_VERSION(2,1,66)
	/* this includes a check for low-latency */
	tty_flip_buffer_push(tty);
#else
	queue_task_irq_off(&tty->flip.tqueue, &tq_timer);
#endif
}

static _INLINE_ void
check_flush_timeout(struct e100_serial *info)
{
	force_eop_if_needed(info);

	flush_to_flip_buffer(info);

	if (info->first_recv_buffer)
		START_FLUSH_FAST_TIMER(info, "flip");
}

#ifdef CONFIG_ETRAX_SERIAL_FAST_TIMER
static void flush_timeout_function(unsigned long data)
{
	struct e100_serial *info = (struct e100_serial *)data;

	fast_timers[info->line].function = NULL;
	serial_fast_timer_expired++;
	TIMERD(DEBUG_LOG(info->line, "flush_timout %i ", info->line));
	TIMERD(DEBUG_LOG(info->line, "num expired: %i\n", serial_fast_timer_expired));
	check_flush_timeout(info);
}

#elif defined(CONFIG_ETRAX_SERIAL_FLUSH_DMA_FAST)

static void 
timeout_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
	struct e100_serial *info;
	int i;
	
#ifdef CONFIG_SVINTO_SIM
	/* No receive in the simulator.  Will probably be when the rest of
	 * the serial interface works, and this piece will just be removed.
	 */
	{
		const char *s = "What? timeout_interrupt in simulator??\n";
		SIMCOUT(s,strlen(s));
	}
	return;
#endif

	/* acknowledge the timer1 irq */
	*R_TIMER_CTRL = r_timer_ctrl_shadow | IO_STATE(R_TIMER_CTRL, i1, clr);
	PROCSTAT(fast_timer_ints++);
	
	for (i = 0; i < NR_PORTS; i++) {
		info = rs_table + i;
		if (info->enabled && info->uses_dma) 
			check_flush_timeout(info);
	}
} /* timeout_interrupt */

#else

/* dma fifo/buffer timeout handler
   forces an end-of-packet for the dma input channel if no chars 
   have been received for CONFIG_ETRAX_SERIAL_RX_TIMEOUT_TICKS/100 s.
   If CONFIG_ETRAX_SERIAL_FLUSH_DMA_FAST is configured then this
   handler is instead run at 15360 Hz.
*/

static struct timer_list flush_timer;

static void 
timed_flush_handler(unsigned long ptr)
{
	struct e100_serial *info;
	int i;

#ifdef CONFIG_SVINTO_SIM
	return;
#endif
	
	for (i = 0; i < NR_PORTS; i++) {
		info = rs_table + i;
		if (info->uses_dma) 
			check_flush_timeout(info);
	}

	/* restart flush timer */
	mod_timer(&flush_timer, jiffies + CONFIG_ETRAX_SERIAL_RX_TIMEOUT_TICKS);
}
#endif

#ifdef SERIAL_HANDLE_EARLY_ERRORS

/* If there is an error (ie break) when the DMA is running and
 * there are no bytes in the fifo the DMA is stopped and we get no
 * eop interrupt. Thus we have to monitor the first bytes on a DMA
 * transfer, and if it is without error we can turn the serial
 * interrupts off.
 */

/*
BREAK handling on ETRAX 100:
ETRAX will generate interrupt although there is no stop bit between the
characters.

Depending on how long the break sequence is, the end of the breaksequence
will look differently:
| indicates start/end of a character.

B= Break character (0x00) with framing error.
E= Error byte with parity error received after B characters.
F= "Faked" valid byte received immediatly after B characters.
V= Valid byte

1.
    B          BL         ___________________________ V
.._|__________|__________|                           |valid data |

Multiple frame errors with data == 0x00 (B),
the timing matches up "perfectly" so no extra ending char is detected.
The RXD pin is 1 in the last interrupt, in that case
we set info->errorcode = ERRCODE_INSERT_BREAK, but we can't really
know if another byte will come and this really is case 2. below 
(e.g F=0xFF or 0xFE)
If RXD pin is 0 we can expect another character (see 2. below).


2.

    B          B          E or F__________________..__ V
.._|__________|__________|______    |                 |valid data
                          "valid" or 
                          parity error

Multiple frame errors with data == 0x00 (B),
but the part of the break trigs is interpreted as a start bit (and possibly
some 0 bits followed by a number of 1 bits and a stop bit).
Depending on parity settings etc. this last character can be either
a fake "valid" char (F) or have a parity error (E).

If the character is valid it will be put in the buffer,
we set info->errorcode = ERRCODE_SET_BREAK so the receive interrupt
will set the flags so the tty will handle it,
if it's an error byte it will not be put in the buffer
and we set info->errorcode = ERRCODE_INSERT_BREAK.

To distinguish a V byte in 1. from an F byte in 2. we keep a timestamp
of the last faulty char (B) and compares it with the current time:
If the time elapsed time is less then 2*char_time_usec we will assume
it's a faked F char and not a Valid char and set 
info->errorcode = ERRCODE_SET_BREAK. 

Flaws in the above solution:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We use the timer to distinguish a F character from a V character,
if a V character is to close after the break we might make the wrong decision.

TODO: The break will be delayed until an F or V character is received.

*/

extern void _INLINE_ handle_ser_interrupt(struct e100_serial *info)
{
	unsigned char rstat = info->port[REG_STATUS];

#ifdef SERIAL_DEBUG_INTR
	printk("Interrupt from serport %d\n", i);
#endif
/*	DEBUG_LOG(info->line, "ser_interrupt stat %03X\n", rstat | (i << 8)); */
	if (rstat & SER_ERROR_MASK) {
		unsigned char data;

		info->last_rx_active_usec = GET_JIFFIES_USEC();
		info->last_rx_active = jiffies;
		/* If we got an error, we must reset it by reading the
		 * data_in field
		 */
		data = info->port[REG_DATA];

		if (!data && (rstat & SER_FRAMING_ERR_MASK)) {
			/* Most likely a break, but we get interrupts over and
			 * over again.
			 */

			if (!info->break_detected_cnt) {
				DEBUG_LOG(info->line, "#BRK start\n", 0);
			}
			if (rstat & SER_RXD_MASK) {
				/* The RX pin is high now, so the break
				 * must be over, but....
				 * we can't really know if we will get another
				 * last byte ending the break or not. 
				 * And we don't know if the byte (if any) will 
				 * have an error or look valid.
				 */
				DEBUG_LOG(info->line, "# BL BRK\n", 0);
				info->errorcode = ERRCODE_INSERT_BREAK;
			}
			info->break_detected_cnt++;
		} else {
			/* The error does not look like a break, but could be
			 * the end of one
			 */
			if (info->break_detected_cnt) {
				DEBUG_LOG(info->line, "EBRK %i\n", info->break_detected_cnt);
				info->errorcode = ERRCODE_INSERT_BREAK;
			} else {
				if (info->errorcode == ERRCODE_INSERT_BREAK)
					add_char_and_flag(info, '\0', TTY_BREAK);

				if (rstat & SER_PAR_ERR_MASK)
					add_char_and_flag(info, data, TTY_PARITY);
				else if (rstat & SER_OVERRUN_MASK)
					add_char_and_flag(info, data, TTY_OVERRUN);
				else if (rstat & SER_FRAMING_ERR_MASK)
					add_char_and_flag(info, data, TTY_FRAME);
				info->errorcode = 0;
			}
			info->break_detected_cnt = 0;
			DEBUG_LOG(info->line, "#iERR s d %04X\n",
			          ((rstat & SER_ERROR_MASK) << 8) | data);
		}
		PROCSTAT(ser_stat[info->line].early_errors_cnt++);
	} else { /* It was a valid byte, now let the DMA do the rest */
		unsigned long curr_time_u = GET_JIFFIES_USEC();
		unsigned long curr_time = jiffies;
		
		if (info->break_detected_cnt) {
			/* Detect if this character is a new valid char or the
			 * last char in a break sequence: If LSBits are 0 and
			 * MSBits are high AND the time is close to the
			 * previous interrupt we should discard it.
			 */
			long elapsed_usec = 
			  (curr_time - info->last_rx_active) * (1000000/HZ) + 
			  curr_time_u - info->last_rx_active_usec;
			if (elapsed_usec < 2*info->char_time_usec) {
				DEBUG_LOG(info->line, "FBRK %i\n", info->line);
				/* Report as BREAK (error) and let
				 * receive_chars() handle it
				 */
				info->errorcode = ERRCODE_SET_BREAK;
			} else {
				DEBUG_LOG(info->line, "Not end of BRK (V)%i\n", info->line);
			}
			DEBUG_LOG(info->line, "num brk %i\n", info->break_detected_cnt);
		}

#ifdef SERIAL_DEBUG_INTR
		printk("** OK, disabling ser_interupts\n");
#endif
		e100_disable_serial_data_irq(info);

		info->break_detected_cnt = 0;

		PROCSTAT(ser_stat[info->line].ser_ints_ok_cnt++);
		DEBUG_LOG(info->line, "ser_int OK %d\n", info->line);
	}

	/* Restarting the DMA never hurts */
	*info->icmdadr = IO_STATE(R_DMA_CH6_CMD, cmd, restart);
	START_FLUSH_FAST_TIMER(info, "ser_int");
} /* handle_ser_interrupt */

static void 
ser_interrupt(int irq, void *dev_id, struct pt_regs *regs)
{
	struct e100_serial *info;
	int i;

	for (i = 0; i < NR_PORTS; i++) {
		info = rs_table + i;