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

	queue_task(&info->tqueue, &tq_serial);
	mark_bh(SERIAL_BH);
}

/* The output DMA channel is free - use it to send as many chars as possible
 * NOTES:
 *   We don't pay attention to info->x_char, which means if the TTY wants to
 *   use XON/XOFF it will set info->x_char but we won't send any X char!
 * 
 *   To implement this, we'd just start a DMA send of 1 byte pointing at a
 *   buffer containing the X char, and skip updating xmit. We'd also have to
 *   check if the last sent char was the X char when we enter this function
 *   the next time, to avoid updating xmit with the sent X value.
 */

static void 
transmit_chars(struct e100_serial *info)
{
	unsigned int c, sentl;
	struct etrax_dma_descr *descr;

#ifdef CONFIG_SVINTO_SIM
	/* This will output too little if tail is not 0 always since
	 * we don't reloop to send the other part. Anyway this SHOULD be a
	 * no-op - transmit_chars would never really be called during sim
	 * since rs_write does not write into the xmit buffer then.
	 */
	if (info->xmit.tail)
		printk("Error in serial.c:transmit_chars(), tail!=0\n");
	if (info->xmit.head != info->xmit.tail) {
		SIMCOUT(info->xmit.buf + info->xmit.tail,
			CIRC_CNT(info->xmit.head,
				 info->xmit.tail,
				 SERIAL_XMIT_SIZE));
		info->xmit.head = info->xmit.tail;  /* move back head */
		info->tr_running = 0;
	}
	return;
#endif
	/* acknowledge both dma_descr and dma_eop irq in R_DMA_CHx_CLR_INTR */
	*info->oclrintradr =
		IO_STATE(R_DMA_CH6_CLR_INTR, clr_descr, do) |
		IO_STATE(R_DMA_CH6_CLR_INTR, clr_eop, do);

#ifdef SERIAL_DEBUG_INTR
	if (info->line == SERIAL_DEBUG_LINE)
		printk("tc\n");
#endif
	if (!info->tr_running) {
		/* weirdo... we shouldn't get here! */
		printk("Achtung: transmit_chars with !tr_running\n");
		return;
	}

	descr = &info->tr_descr;

	/* first get the amount of bytes sent during the last DMA transfer,
	   and update xmit accordingly */

	/* if the stop bit was not set, all data has been sent */
	if (!(descr->status & d_stop)) {
		sentl = descr->sw_len;
	} else 
		/* otherwise we find the amount of data sent here */
		sentl = descr->hw_len;

	/* update stats */
	info->icount.tx += sentl;

	/* update xmit buffer */
	info->xmit.tail = (info->xmit.tail + sentl) & (SERIAL_XMIT_SIZE - 1);

	/* if there is only a few chars left in the buf, wake up the blocked
	   write if any */
	if (CIRC_CNT(info->xmit.head,
		     info->xmit.tail,
		     SERIAL_XMIT_SIZE) < WAKEUP_CHARS)
		rs_sched_event(info, RS_EVENT_WRITE_WAKEUP);

	/* find out the largest amount of consecutive bytes we want to send now */

	c = CIRC_CNT_TO_END(info->xmit.head, info->xmit.tail, SERIAL_XMIT_SIZE);

	if (c <= 0) {
		/* our job here is done, don't schedule any new DMA transfer */
		info->tr_running = 0;

#if defined(CONFIG_ETRAX_RS485) && defined(CONFIG_ETRAX_FAST_TIMER)
		if (info->rs485.enabled) {
			/* Set a short timer to toggle RTS */
			start_one_shot_timer(&fast_timers_rs485[info->line],
			                     rs485_toggle_rts_timer_function,
			                     (unsigned long)info,
			                     info->char_time_usec*2,
			                     "RS-485");
		}
#endif /* RS485 */
		return;
	}

	/* ok we can schedule a dma send of c chars starting at info->xmit.tail */
	/* set up the descriptor correctly for output */

	descr->ctrl = d_int | d_eol | d_wait; /* Wait needed for tty_wait_until_sent() */
	descr->sw_len = c;
	descr->buf = virt_to_phys(info->xmit.buf + info->xmit.tail);
	descr->status = 0;

	*info->ofirstadr = virt_to_phys(descr); /* write to R_DMAx_FIRST */
	*info->ocmdadr = 1;       /* dma command start -> R_DMAx_CMD */
	
	/* DMA is now running (hopefully) */
} /* transmit_chars */

static void 
start_transmit(struct e100_serial *info)
{
#if 0
	if (info->line == SERIAL_DEBUG_LINE)
		printk("x\n");
#endif

	info->tr_descr.sw_len = 0;
	info->tr_descr.hw_len = 0;
	info->tr_descr.status = 0;
	info->tr_running = 1;

	transmit_chars(info);
} /* start_transmit */

#ifdef CONFIG_ETRAX_SERIAL_FAST_TIMER
static int serial_fast_timer_started = 0;
static int serial_fast_timer_expired = 0;
static void flush_timeout_function(unsigned long data);
#define START_FLUSH_FAST_TIMER(info, string) {\
  unsigned long timer_flags; \
  save_flags(timer_flags); \
  cli(); \
  if (fast_timers[info->line].function == NULL) { \
    serial_fast_timer_started++; \
    TIMERD(DEBUG_LOG(info->line, "start_timer %i ", info->line)); \
    TIMERD(DEBUG_LOG(info->line, "num started: %i\n", serial_fast_timer_started)); \
    start_one_shot_timer(&fast_timers[info->line], \
                         flush_timeout_function, \
                         (unsigned long)info, \
                         info->char_time_usec*4, \
                         string); \
  } \
  else { \
    TIMERD(DEBUG_LOG(info->line, "timer %i already running\n", info->line)); \
  } \
  restore_flags(timer_flags); \
}

#else
#define START_FLUSH_FAST_TIMER(info, string)
#endif

static struct etrax_recv_buffer *
alloc_recv_buffer(unsigned int size)
{
	struct etrax_recv_buffer *buffer;

	if (!(buffer = kmalloc(sizeof *buffer + size, GFP_ATOMIC)))
		return NULL;

	buffer->next = NULL;
	buffer->length = 0;
	buffer->error = TTY_NORMAL;

	return buffer;
}

static void
append_recv_buffer(struct e100_serial *info, struct etrax_recv_buffer *buffer)
{
	unsigned long flags;

	save_flags(flags);
	cli();

	if (!info->first_recv_buffer)
		info->first_recv_buffer = buffer;
	else
		info->last_recv_buffer->next = buffer;

	info->last_recv_buffer = buffer;

	info->recv_cnt += buffer->length;
	if (info->recv_cnt > info->max_recv_cnt)
		info->max_recv_cnt = info->recv_cnt;

	restore_flags(flags);
}

static int
add_char_and_flag(struct e100_serial *info, unsigned char data, unsigned char flag)
{
	struct etrax_recv_buffer *buffer;

	if (!(buffer = alloc_recv_buffer(4)))
		return 0;

	buffer->length = 1;
	buffer->error = flag;
	buffer->buffer[0] = data;
	
	append_recv_buffer(info, buffer);

	info->icount.rx++;

	return 1;
}

extern _INLINE_ unsigned int
handle_descr_data(struct e100_serial *info, struct etrax_dma_descr *descr, unsigned int recvl)
{
	struct etrax_recv_buffer *buffer = phys_to_virt(descr->buf) - sizeof *buffer;

	if (info->recv_cnt + recvl > 65536) {
		printk(__FUNCTION__ ": Too much pending incoming serial data! Dropping %u bytes.\n", recvl);
		return 0;
	}

	buffer->length = recvl;

	if (info->errorcode == ERRCODE_SET_BREAK)
		buffer->error = TTY_BREAK;
	info->errorcode = 0;

	append_recv_buffer(info, buffer);

	if (!(buffer = alloc_recv_buffer(SERIAL_DESCR_BUF_SIZE)))
		panic(__FUNCTION__ ": Failed to allocate memory for receive buffer!\n");

	descr->buf = virt_to_phys(buffer->buffer);
	
	return recvl;
}

static _INLINE_ unsigned int
handle_all_descr_data(struct e100_serial *info)
{
	struct etrax_dma_descr *descr;
	unsigned int recvl;
	unsigned int ret = 0;

	while (1)
	{
		descr = &info->rec_descr[info->cur_rec_descr];

		if (descr == phys_to_virt(*info->idescradr))
			break;

		if (++info->cur_rec_descr == SERIAL_RECV_DESCRIPTORS)
			info->cur_rec_descr = 0;
	
		/* find out how many bytes were read */

		/* if the eop bit was not set, all data has been received */
		if (!(descr->status & d_eop)) {
			recvl = descr->sw_len;
		} else {
			/* otherwise we find the amount of data received here */
			recvl = descr->hw_len;
		}

		/* Reset the status information */
		descr->status = 0;

		DEBUG_LOG(info->line, "recvl %lu\n", recvl);

		/* update stats */
		info->icount.rx += recvl;

		ret += handle_descr_data(info, descr, recvl);
	}

	return ret;
}

static _INLINE_ void 
receive_chars(struct e100_serial *info)
{
	struct tty_struct *tty;
	unsigned char rstat;

#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.
	 */
	return;
#endif

	/* Acknowledge both dma_descr and dma_eop irq in R_DMA_CHx_CLR_INTR */
	*info->iclrintradr =
		IO_STATE(R_DMA_CH6_CLR_INTR, clr_descr, do) |
		IO_STATE(R_DMA_CH6_CLR_INTR, clr_eop, do);

	tty = info->tty;
	if (!tty) /* Something wrong... */
		return;

#ifdef SERIAL_HANDLE_EARLY_ERRORS
	e100_enable_serial_data_irq(info);
#endif	

	if (info->errorcode == ERRCODE_INSERT_BREAK)
		add_char_and_flag(info, '\0', TTY_BREAK);

	handle_all_descr_data(info);

	/* Read the status register to detect errors */
	rstat = info->port[REG_STATUS];

	if (rstat & SER_ERROR_MASK) {
		/* If we got an error, we must reset it by reading the
		 * data_in field
		 */
		unsigned char data = info->port[REG_DATA];

		PROCSTAT(ser_stat[info->line].errors_cnt++);
		DEBUG_LOG(info->line, "#dERR: s d 0x%04X\n",
			  ((rstat & SER_ERROR_MASK) << 8) | data);

		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);
	}

	START_FLUSH_FAST_TIMER(info, "receive_chars");

	/* Restart the receiving DMA */
	*info->icmdadr = IO_STATE(R_DMA_CH6_CMD, cmd, restart);
}

static _INLINE_ int
start_recv_dma(struct e100_serial *info)
{
	struct etrax_dma_descr *descr = info->rec_descr;
	struct etrax_recv_buffer *buffer;
        int i;

	/* Set up the receiving descriptors */
	for (i = 0; i < SERIAL_RECV_DESCRIPTORS; i++) {
		if (!(buffer = alloc_recv_buffer(SERIAL_DESCR_BUF_SIZE)))
			panic(__FUNCTION__ ": Failed to allocate memory for receive buffer!\n");

		descr[i].ctrl = d_int;
		descr[i].buf = virt_to_phys(buffer->buffer);
		descr[i].sw_len = SERIAL_DESCR_BUF_SIZE;
		descr[i].hw_len = 0;
		descr[i].status = 0;
		descr[i].next = virt_to_phys(&descr[i+1]);
	}

	/* Link the last descriptor to the first */
	descr[i-1].next = virt_to_phys(&descr[0]);

	/* Start with the first descriptor in the list */
	info->cur_rec_descr = 0;

	/* Start the DMA */
	*info->ifirstadr = virt_to_phys(&descr[info->cur_rec_descr]);
	*info->icmdadr = IO_STATE(R_DMA_CH6_CMD, cmd, start);

	/* Input DMA should be running now */
	return 1;
}

static void 
start_receive(struct e100_serial *info)
{
#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.
	 */
	return;
#endif

	/* reset the input dma channel to be sure it works */

	*info->icmdadr = IO_STATE(R_DMA_CH6_CMD, cmd, reset);
	while (IO_EXTRACT(R_DMA_CH6_CMD, cmd, *info->icmdadr) ==
	       IO_STATE_VALUE(R_DMA_CH6_CMD, cmd, reset));

	info->tty->flip.count = 0;

	start_recv_dma(info);
	
#ifdef CONFIG_ETRAX_SERIAL_FLUSH_DMA_FAST
	start_flush_timer();
#endif
}


static _INLINE_ void 
status_handle(struct e100_serial *info, unsigned short status)
{
}

/* the bits in the MASK2 register are laid out like this:
   DMAI_EOP DMAI_DESCR DMAO_EOP DMAO_DESCR
   where I is the input channel and O is the output channel for the port.
   info->irq is the bit number for the DMAO_DESCR so to check the others we
   shift info->irq to the left.
*/

/* dma output channel interrupt handler
   this interrupt is called from DMA2(ser2), DMA4(ser3), DMA6(ser0) or
   DMA8(ser1) when they have finished a descriptor with the intr flag set.
*/

static void 
tr_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? tr_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 */