serial.c

linux平台上的开放源代码的网络摄像机程序.实现视频捕捉,传输以及云台控制等.非常具有参考价值.

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.

*/

static 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;

		if (!info->uses_dma) 
			continue; 

		/* Which line caused the irq? */
		if (*R_IRQ_MASK1_RD & (1U << (8+2*info->line))) { 
			handle_ser_interrupt(info);
		}
	}
} /* ser_interrupt */
#endif

/*
 * -------------------------------------------------------------------
 * Here ends the serial interrupt routines.
 * -------------------------------------------------------------------
 */

/*
 * This routine is used to handle the "bottom half" processing for the
 * serial driver, known also the "software interrupt" processing.
 * This processing is done at the kernel interrupt level, after the
 * rs_interrupt() has returned, BUT WITH INTERRUPTS TURNED ON.  This
 * is where time-consuming activities which can not be done in the
 * interrupt driver proper are done; the interrupt driver schedules
 * them using rs_sched_event(), and they get done here.
 */
static void 
do_serial_bh(void)
{
	run_task_queue(&tq_serial);
}

static void 
do_softint(void *private_)
{
	struct e100_serial	*info = (struct e100_serial *) private_;
	struct tty_struct	*tty;
	
	tty = info->tty;
	if (!tty)
		return;
	
	if (test_and_clear_bit(RS_EVENT_WRITE_WAKEUP, &info->event)) {
		if ((tty->flags & (1 << TTY_DO_WRITE_WAKEUP)) &&
		    tty->ldisc.write_wakeup)
			(tty->ldisc.write_wakeup)(tty);
		wake_up_interruptible(&tty->write_wait);
	}
}

/*
 * This routine is called from the scheduler tqueue when the interrupt
 * routine has signalled that a hangup has occurred.  The path of
 * hangup processing is:
 *
 * 	serial interrupt routine -> (scheduler tqueue) ->
 * 	do_serial_hangup() -> tty->hangup() -> rs_hangup()
 * 
 */
static void 
do_serial_hangup(void *private_)
{
	struct e100_serial	*info = (struct e100_serial *) private_;
	struct tty_struct	*tty;

	tty = info->tty;
	if (!tty)
		return;
	
	tty_hangup(tty);
}

static int 
startup(struct e100_serial * info)
{
	unsigned long flags;
	unsigned long xmit_page;
	unsigned char *recv_page;

	xmit_page = get_zeroed_page(GFP_KERNEL);
	if (!xmit_page)
		return -ENOMEM;

	recv_page = kmalloc(2 * SERIAL_RECV_SIZE + SERIAL_RECV_DESCRIPTORS * SERIAL_DESCR_BUF_SIZE, GFP_KERNEL);
	if (!recv_page) {
		free_page(xmit_page);
		return -ENOMEM;
	}

	save_flags(flags); cli();

	/* if it was already initialized, skip this */

	if (info->flags & ASYNC_INITIALIZED) {
		restore_flags(flags);
		free_page(xmit_page);
		kfree(recv_page);
		return 0;
	}

	if (info->xmit.buf)
		free_page(xmit_page);
	else
		info->xmit.buf = (unsigned char *) xmit_page;

	if (info->recv.buf)
		kfree(recv_page);
	else {
		info->recv.buf = (unsigned char *) recv_page;
		info->flag_buf = info->recv.buf + SERIAL_RECV_SIZE;
	}

#ifdef SERIAL_DEBUG_OPEN
	printk("starting up ttyS%d (xmit_buf 0x%p, recv_buf 0x%p)...\n", info->line, info->xmit.buf, info->recv.buf);
#endif

#ifdef CONFIG_SVINTO_SIM
	/* Bits and pieces collected from below.  Better to have them
	   in one ifdef:ed clause than to mix in a lot of ifdefs,
	   right? */
	if (info->tty)
		clear_bit(TTY_IO_ERROR, &info->tty->flags);
	info->xmit.head = info->xmit.tail = 0;
	info->recv.head = info->recv.tail = 0;

	/* No real action in the simulator, but may set info important
	   to ioctl. */
	change_speed(info);
#else

	/*
	 * Clear the FIFO buffers and disable them
	 * (they will be reenabled in change_speed())
	 */

	/*
	 * Reset the DMA channels and make sure their interrupts are cleared
	 */

	info->uses_dma = 1;
	*info->icmdadr = IO_STATE(R_DMA_CH6_CMD, cmd, reset);
	*info->ocmdadr = IO_STATE(R_DMA_CH6_CMD, cmd, reset);

	/* Wait until reset cycle is complete */
	while (IO_EXTRACT(R_DMA_CH6_CMD, cmd, *info->icmdadr) ==
	       IO_STATE_VALUE(R_DMA_CH6_CMD, cmd, reset));

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

	/* Make sure the irqs are cleared */
	*info->iclrintradr =
		IO_STATE(R_DMA_CH6_CLR_INTR, clr_descr, do) |
		IO_STATE(R_DMA_CH6_CLR_INTR, clr_eop, do);
	*info->oclrintradr =
		IO_STATE(R_DMA_CH6_CLR_INTR, clr_descr, do) |
		IO_STATE(R_DMA_CH6_CLR_INTR, clr_eop, do);

	if (info->tty)
		clear_bit(TTY_IO_ERROR, &info->tty->flags);

	info->xmit.head = info->xmit.tail = 0;
	info->recv.head = info->recv.tail = 0;
	
	/*
	 * and set the speed and other flags of the serial port
	 * this will start the rx/tx as well
	 */
#ifdef SERIAL_HANDLE_EARLY_ERRORS
	e100_enable_serial_data_irq(info);
#endif	
	change_speed(info);

	/* dummy read to reset any serial errors */

	(void)info->port[REG_DATA];

	/* enable the interrupts */

	e100_enable_txdma_irq(info);
	e100_enable_rxdma_irq(info);

	info->tr_running = 0; /* to be sure we don't lock up the transmitter */

	/* setup the dma input descriptor and start dma */
	
	start_receive(info);
	
	/* for safety, make sure the descriptors last result is 0 bytes written */
	
	info->tr_descr.sw_len = 0;
	info->tr_descr.hw_len = 0;
	info->tr_descr.status = 0;

	/* enable RTS/DTR last */

	e100_rts(info, 1);
	e100_dtr(info, 1);
		
#endif /* CONFIG_SVINTO_SIM */
	
	info->flags |= ASYNC_INITIALIZED;
	
	restore_flags(flags);
	return 0;
}

/*
 * This routine will shutdown a serial port; interrupts are disabled, and
 * DTR is dropped if the hangup on close termio flag is on.
 */
static void 
shutdown(struct e100_serial * info)
{
	unsigned long flags;

#ifndef CONFIG_SVINTO_SIM	
	/* shut down the transmitter and receiver */

	e100_disable_rx(info);
	info->port[REG_TR_CTRL] = (info->tx_ctrl &= ~0x40);

	e100_disable_rxdma_irq(info);
	e100_disable_txdma_irq(info);

	info->tr_running = 0;

	/* reset both dma channels */

	*info->icmdadr = IO_STATE(R_DMA_CH6_CMD, cmd, reset);
	*info->ocmdadr = IO_STATE(R_DMA_CH6_CMD, cmd, reset);
	info->uses_dma = 0;

#endif /* CONFIG_SVINTO_SIM */

	if (!(info->flags & ASYNC_INITIALIZED))
		return;
	
#ifdef SERIAL_DEBUG_OPEN
	printk("Shutting down serial port %d (irq %d)....\n", info->line,
	       info->irq);
#endif
	
	save_flags(flags);
	cli(); /* Disable interrupts */
	
	if (info->xmit.buf) {
		free_page((unsigned long)info->xmit.buf);
		info->xmit.buf = NULL;
	}

	if (info->recv.buf) {
		kfree(info->recv.buf);
		info->recv.buf = NULL;
		info->flag_buf = NULL;
	}

	if (!info->tty || (info->tty->termios->c_cflag & HUPCL)) {
		/* hang up DTR and RTS if HUPCL is enabled */
		e100_dtr(info, 0);
		e100_rts(info, 0); /* could check CRTSCTS before doing this */
	}

	if (info->tty)
		set_bit(TTY_IO_ERROR, &info->tty->flags);
	
	info->flags &= ~ASYNC_INITIALIZED;
	restore_flags(flags);
}


/* change baud rate and other assorted parameters */

static void 
change_speed(struct e100_serial *info)
{
	unsigned int cflag;

	/* first some safety checks */
	
	if (!info->tty || !info->tty->termios)
		return;
	if (!info->port)
		return;
	
	cflag = info->tty->termios->c_cflag;
	
	/* possibly, the tx/rx should be disabled first to do this safely */
	
	/* change baud-rate and write it to the hardware */
	
	info->baud = cflag_to_baud(cflag);
	
#ifndef CONFIG_SVINTO_SIM
	info->port[REG_BAUD] = cflag_to_etrax_baud(cflag);
	/* start with default settings and then fill in changes */

	/* 8 bit, no/even parity */
	info->rx_ctrl &= ~(IO_MASK(R_SERIAL0_REC_CTRL, rec_bitnr) |
			   IO_MASK(R_SERIAL0_REC_CTRL, rec_par_en) |
			   IO_MASK(R_SERIAL0_R