l1.c

讲述linux的初始化过程

#define L1SC_RECV_UNLOCK(l,pl)				\
     { if( (l)->uart == BRL1_LOCALUART )		\
	 mutex_spinunlock( &((l)->recv_lock), (pl)); }


/*********************************************************************
 * subchannel manipulation 
 *
 * The SUBCH_[UN]LOCK macros are used to arbitrate subchannel
 * allocation.  SUBCH_DATA_[UN]LOCK control access to data structures
 * associated with particular subchannels (e.g., receive queues).
 *
 */


#ifdef SPINLOCKS_WORK
#define SUBCH_LOCK(sc,pl) \
     (pl) = mutex_spinlock_spl( &((sc)->subch_lock), spl7 )
#define SUBCH_UNLOCK(sc,pl) \
     mutex_spinunlock( &((sc)->subch_lock), (pl) )

#define SUBCH_DATA_LOCK(sbch,pl) \
     (pl) = mutex_spinlock_spl( &((sbch)->data_lock), spl7 )
#define SUBCH_DATA_UNLOCK(sbch,pl) \
     mutex_spinunlock( &((sbch)->data_lock), (pl) )
#else
#define SUBCH_LOCK(sc,pl) 
#define SUBCH_UNLOCK(sc,pl)
#define SUBCH_DATA_LOCK(sbch,pl)
#define SUBCH_DATA_UNLOCK(sbch,pl)
#endif	/* SPINLOCKS_WORK */

/*
 * set a function to be called for subchannel ch in the event of
 * a transmission low-water interrupt from the uart
 */
void
subch_set_tx_notify( l1sc_t *sc, int ch, brl1_notif_t func )
{
    int pl;
    L1SC_SEND_LOCK( sc, pl );
    sc->subch[ch].tx_notify = func;
    
    /* some upper layer is asking to be notified of low-water, but if the 
     * send buffer isn't already in use, we're going to need to get the
     * interrupts going on the uart...
     */
    if( func && !sc->send_in_use )
	uart_enable_xmit_intr( sc );
    L1SC_SEND_UNLOCK(sc, pl );
}

/*
 * set a function to be called for subchannel ch when data is received
 */
void
subch_set_rx_notify( l1sc_t *sc, int ch, brl1_notif_t func )
{
#ifdef SPINLOCKS_WORK
    int pl;
#endif
    brl1_sch_t *subch = &(sc->subch[ch]);

    SUBCH_DATA_LOCK( subch, pl );
    sc->subch[ch].rx_notify = func;
    SUBCH_DATA_UNLOCK( subch, pl );
}



/* get_myid is an internal function that reads the PI_CPU_NUM
 * register of the local bedrock to determine which of the
 * four possible CPU's "this" one is
 */
static int
get_myid( void )
{
    return( LD(LOCAL_HUB(PI_CPU_NUM)) );
}



/*********************************************************************
 * Queue manipulation macros
 *
 *
 */
#define NEXT(p)         (((p) + 1) & (BRL1_QSIZE-1)) /* assume power of 2 */

#define cq_init(q)      bzero((q), sizeof (*(q)))
#define cq_empty(q)     ((q)->ipos == (q)->opos)
#define cq_full(q)      (NEXT((q)->ipos) == (q)->opos)
#define cq_used(q)      ((q)->opos <= (q)->ipos ?                       \
                         (q)->ipos - (q)->opos :                        \
                         BRL1_QSIZE + (q)->ipos - (q)->opos)
#define cq_room(q)      ((q)->opos <= (q)->ipos ?                       \
                         BRL1_QSIZE - 1 + (q)->opos - (q)->ipos :       \
                         (q)->opos - (q)->ipos - 1)
#define cq_add(q, c)    ((q)->buf[(q)->ipos] = (u_char) (c),            \
                         (q)->ipos = NEXT((q)->ipos))
#define cq_rem(q, c)    ((c) = (q)->buf[(q)->opos],                     \
                         (q)->opos = NEXT((q)->opos))
#define cq_discard(q)	((q)->opos = NEXT((q)->opos))

#define cq_tent_full(q)	(NEXT((q)->tent_next) == (q)->opos)
#define cq_tent_len(q)	((q)->ipos <= (q)->tent_next ?			\
			 (q)->tent_next - (q)->ipos :			\
			 BRL1_QSIZE + (q)->tent_next - (q)->ipos)
#define cq_tent_add(q, c)						\
			((q)->buf[(q)->tent_next] = (u_char) (c),	\
			 (q)->tent_next = NEXT((q)->tent_next))
#define cq_commit_tent(q)						\
			((q)->ipos = (q)->tent_next)
#define cq_discard_tent(q)						\
			((q)->tent_next = (q)->ipos)




/*********************************************************************
 * CRC-16 (for checking bedrock/L1 packets).
 *
 * These are based on RFC 1662 ("PPP in HDLC-like framing").
 */

static unsigned short fcstab[256] = {
      0x0000, 0x1189, 0x2312, 0x329b, 0x4624, 0x57ad, 0x6536, 0x74bf,
      0x8c48, 0x9dc1, 0xaf5a, 0xbed3, 0xca6c, 0xdbe5, 0xe97e, 0xf8f7,
      0x1081, 0x0108, 0x3393, 0x221a, 0x56a5, 0x472c, 0x75b7, 0x643e,
      0x9cc9, 0x8d40, 0xbfdb, 0xae52, 0xdaed, 0xcb64, 0xf9ff, 0xe876,
      0x2102, 0x308b, 0x0210, 0x1399, 0x6726, 0x76af, 0x4434, 0x55bd,
      0xad4a, 0xbcc3, 0x8e58, 0x9fd1, 0xeb6e, 0xfae7, 0xc87c, 0xd9f5,
      0x3183, 0x200a, 0x1291, 0x0318, 0x77a7, 0x662e, 0x54b5, 0x453c,
      0xbdcb, 0xac42, 0x9ed9, 0x8f50, 0xfbef, 0xea66, 0xd8fd, 0xc974,
      0x4204, 0x538d, 0x6116, 0x709f, 0x0420, 0x15a9, 0x2732, 0x36bb,
      0xce4c, 0xdfc5, 0xed5e, 0xfcd7, 0x8868, 0x99e1, 0xab7a, 0xbaf3,
      0x5285, 0x430c, 0x7197, 0x601e, 0x14a1, 0x0528, 0x37b3, 0x263a,
      0xdecd, 0xcf44, 0xfddf, 0xec56, 0x98e9, 0x8960, 0xbbfb, 0xaa72,
      0x6306, 0x728f, 0x4014, 0x519d, 0x2522, 0x34ab, 0x0630, 0x17b9,
      0xef4e, 0xfec7, 0xcc5c, 0xddd5, 0xa96a, 0xb8e3, 0x8a78, 0x9bf1,
      0x7387, 0x620e, 0x5095, 0x411c, 0x35a3, 0x242a, 0x16b1, 0x0738,
      0xffcf, 0xee46, 0xdcdd, 0xcd54, 0xb9eb, 0xa862, 0x9af9, 0x8b70,
      0x8408, 0x9581, 0xa71a, 0xb693, 0xc22c, 0xd3a5, 0xe13e, 0xf0b7,
      0x0840, 0x19c9, 0x2b52, 0x3adb, 0x4e64, 0x5fed, 0x6d76, 0x7cff,
      0x9489, 0x8500, 0xb79b, 0xa612, 0xd2ad, 0xc324, 0xf1bf, 0xe036,
      0x18c1, 0x0948, 0x3bd3, 0x2a5a, 0x5ee5, 0x4f6c, 0x7df7, 0x6c7e,
      0xa50a, 0xb483, 0x8618, 0x9791, 0xe32e, 0xf2a7, 0xc03c, 0xd1b5,
      0x2942, 0x38cb, 0x0a50, 0x1bd9, 0x6f66, 0x7eef, 0x4c74, 0x5dfd,
      0xb58b, 0xa402, 0x9699, 0x8710, 0xf3af, 0xe226, 0xd0bd, 0xc134,
      0x39c3, 0x284a, 0x1ad1, 0x0b58, 0x7fe7, 0x6e6e, 0x5cf5, 0x4d7c,
      0xc60c, 0xd785, 0xe51e, 0xf497, 0x8028, 0x91a1, 0xa33a, 0xb2b3,
      0x4a44, 0x5bcd, 0x6956, 0x78df, 0x0c60, 0x1de9, 0x2f72, 0x3efb,
      0xd68d, 0xc704, 0xf59f, 0xe416, 0x90a9, 0x8120, 0xb3bb, 0xa232,
      0x5ac5, 0x4b4c, 0x79d7, 0x685e, 0x1ce1, 0x0d68, 0x3ff3, 0x2e7a,
      0xe70e, 0xf687, 0xc41c, 0xd595, 0xa12a, 0xb0a3, 0x8238, 0x93b1,
      0x6b46, 0x7acf, 0x4854, 0x59dd, 0x2d62, 0x3ceb, 0x0e70, 0x1ff9,
      0xf78f, 0xe606, 0xd49d, 0xc514, 0xb1ab, 0xa022, 0x92b9, 0x8330,
      0x7bc7, 0x6a4e, 0x58d5, 0x495c, 0x3de3, 0x2c6a, 0x1ef1, 0x0f78
};

#define INIT_CRC	0xFFFF	/* initial CRC value	  */
#define	GOOD_CRC	0xF0B8	/* "good" final CRC value */

static unsigned short crc16_calc( unsigned short crc, u_char c )
{
    return( (crc >> 8) ^ fcstab[(crc ^ c) & 0xff] );
}


/***********************************************************************
 * The following functions implement the PPP-like bedrock/L1 protocol
 * layer.
 *
 */

#define BRL1_FLAG_CH	0x7e
#define BRL1_ESC_CH	0x7d
#define BRL1_XOR_CH	0x20

/* L1<->Bedrock packet types */
#define BRL1_REQUEST    0x00
#define BRL1_RESPONSE   0x20
#define BRL1_EVENT      0x40

#define BRL1_PKT_TYPE_MASK      0xE0
#define BRL1_SUBCH_MASK         0x1F

#define PKT_TYPE(tsb)   ((tsb) & BRL1_PKT_TYPE_MASK)
#define SUBCH(tsb)	((tsb) & BRL1_SUBCH_MASK)

/* timeouts */
#define BRL1_INIT_TIMEOUT	500000

extern l1sc_t * get_elsc( void );

/*
 * brl1_discard_packet is a dummy "receive callback" used to get rid
 * of packets we don't want
 */
void brl1_discard_packet( l1sc_t *sc, int ch )
{
    int pl;
    brl1_sch_t *subch = &sc->subch[ch];
    sc_cq_t *q = subch->iqp;
    SUBCH_DATA_LOCK( subch, pl );
    q->opos = q->ipos;
    atomicClearInt( &(subch->packet_arrived), ~((unsigned)0) );
    SUBCH_DATA_UNLOCK( subch, pl );
}


/*
 * brl1_send_chars sends the send buffer in the l1sc_t structure
 * out through the uart.  Assumes that the caller has locked the
 * UART (or send buffer in the kernel).
 *
 * This routine doesn't block-- if you want it to, call it in
 * a loop.
 */
static int
brl1_send_chars( l1sc_t *sc )
{
    /* In the kernel, we track the depth of the C brick's UART's
     * fifo in software, and only check if the UART is accepting
     * characters when our count indicates that the fifo should
     * be full.
     *
     * For remote (router) UARTs, and also for the local (C brick)
     * UART in the prom, we check with the UART before sending every
     * character.
     */
    if( sc->uart == BRL1_LOCALUART ) 
    {
	CONS_HW_LOCK(1);
	if( !(sc->fifo_space) && UART_PUTC_READY( sc->nasid ) )
//	    sc->fifo_space = UART_FIFO_DEPTH;
	    sc->fifo_space = 1000;
	
	while( (sc->sent < sc->send_len) && (sc->fifo_space) ) {
	    uart_putc( sc );
	    sc->fifo_space--;
	    sc->sent++;
	}

	CONS_HW_UNLOCK(1);
    }

    else

    /* The following applies to all UARTs in the prom, and to remote
     * (router) UARTs in the kernel...
     */

#define TIMEOUT_RETRIES	30

    {
	int result;
	int tries = 0;

	while( sc->sent < sc->send_len ) {
	    result = sc->putc_f( sc );
	    if( result >= 0 ) {
		(sc->sent)++;
		continue;
	    }
	    if( result == UART_TIMEOUT ) {
		tries++;
		/* send this character in TIMEOUT_RETRIES... */
		if( tries < TIMEOUT_RETRIES ) {
		    continue;
		}
		/* ...or else... */
		else {
		    /* ...drop the packet. */
		    sc->sent = sc->send_len;
		    return sc->send_len;
		}
	    }
	    if( result < 0 ) {
		return result;
	    }
	}
    }
    
    return sc->sent;
}


/* brl1_send formats up a packet and (at least begins to) send it
 * to the uart.  If the send buffer is in use when this routine obtains
 * the lock, it will behave differently depending on the "wait" parameter.
 * For wait == 0 (most I/O), it will return 0 (as in "zero bytes sent"),
 * hopefully encouraging the caller to back off (unlock any high-level 
 * spinlocks) and allow the buffer some time to drain.  For wait==1 (high-
 * priority I/O along the lines of kernel error messages), we will flush
 * the current contents of the send buffer and beat on the uart
 * until our message has been completely transmitted.
 */

int
brl1_send( l1sc_t *sc, char *msg, int len, u_char type_and_subch, int wait )
{
    int pl;
    int index;
    int pkt_len = 0;
    unsigned short crc = INIT_CRC;
    char *send_ptr = sc->send;

    L1SC_SEND_LOCK(sc, pl);

    if( sc->send_in_use ) {
	if( !wait ) {
	    L1SC_SEND_UNLOCK(sc, pl);
	    return 0; /* couldn't send anything; wait for buffer to drain */
	}
	else {
	    /* buffer's in use, but we're synchronous I/O, so we're going
	     * to send whatever's in there right now and take the buffer
	     */
	    while( sc->sent < sc->send_len )
		brl1_send_chars( sc );
	}
    }
    else {
	sc->send_in_use = 1;
    }
    *send_ptr++ = BRL1_FLAG_CH;
    *send_ptr++ = type_and_subch;
    pkt_len += 2;
    crc = crc16_calc( crc, type_and_subch );

    /* limit number of characters accepted to max payload size */
    if( len > (BRL1_QSIZE - 1) )
	len = (BRL1_QSIZE - 1);

    /* copy in the message buffer (inserting PPP 
     * framing info where necessary)
     */
    for( index = 0; index < len; index++ ) {

	switch( *msg ) {
	    
	  case BRL1_FLAG_CH:
	    *send_ptr++ = BRL1_ESC_CH;
	    *send_ptr++ = (*msg) ^ BRL1_XOR_CH;
	    pkt_len += 2;
	    break;
	    
	  case BRL1_ESC_CH:
	    *send_ptr++ = BRL1_ESC_CH;
	    *send_ptr++ = (*msg) ^ BRL1_XOR_CH;
	    pkt_len += 2;
	    break;
	    
	  default:
	    *send_ptr++ = *msg;
	    pkt_len++;
	}
	crc = crc16_calc( crc, *msg );
	msg++;
    }
    crc ^= 0xffff;

    for( index = 0; index < sizeof(crc); index++ ) {
	char crc_char = (char)(crc & 0x00FF);
	if( (crc_char == BRL1_ESC_CH) || (crc_char == BRL1_FLAG_CH) ) {
	    *send_ptr++ = BRL1_ESC_CH;
	    pkt_len++;
	    crc_char ^= BRL1_XOR_CH;
	}
	*send_ptr++ = crc_char;
	pkt_len++;
	crc >>= 8;
    }
    
    *send_ptr++ = BRL1_FLAG_CH;
    pkt_len++;

    sc->send_len = pkt_len;
    sc->sent = 0;

    do {
	brl1_send_chars( sc );
    } while( (sc->sent < sc->send_len) && wait );

    if( sc->sent == sc->send_len ) {
	/* success! release the send buffer */
	sc->send_in_use = 0;
    }
    else if( !wait ) {
	/* enable low-water interrupts so buffer will be drained */
	uart_enable_xmit_intr(sc);
    }
    L1SC_SEND_UNLOCK(sc, pl);
    return len;
}


/* brl1_send_cont is intended to be called as an interrupt service
 * routine.  It sends until the UART won't accept any more characters,
 * or until an error is encountered (in which case we surrender the
 * send buffer and give up trying to send the packet).  Once the
 * last character in the packet has been sent, this routine releases
 * the send buffer and calls any previously-registered "low-water"
 * output routines.
 */
int
brl1_send_cont( l1sc_t *sc )
{
    int pl;
    int done = 0;
    brl1_notif_t callups[BRL1_NUM_SUBCHANS];
    brl1_notif_t *callup;
    brl1_sch_t *subch;
    int index;

    L1SC_SEND_LOCK(sc, pl);
    brl1_send_chars( sc );
    done = (sc->sent == sc->send_len);
    if( done ) {

	sc->send_in_use = 0;
	uart_disable_xmit_intr(sc);

	/* collect pointers to callups *before* unlocking */
	subch = sc->subch;
	callup = callups;
	for( index = 0; index < BRL1_NUM_SUBCHANS; index++ ) {
	    *callup = subch->tx_notify;
	    subch++;
	    callup++;
	}
    }
    L1SC_SEND_UNLOCK(sc, pl);

    if( done ) {
	/* call any upper layer that's asked for low-water notification */
	callup = callups;
	for( index = 0; index < BRL1_NUM_SUBCHANS; index++ ) {
	    if( *callup )
		(*(*callup))( sc, index );
	    callup++;
	}
    }
    return 0;
}


/* internal function -- used by brl1_receive to read a character 
 * from the uart and check whether errors occurred in the process.
 */
static int
read_uart( l1sc_t *sc, int *c, int *result )
{
    *c = sc->getc_f( sc );

    /* no character is available */
    if( *c == UART_NO_CHAR ) {
	*result = BRL1_NO_MESSAGE;
	return 0;
    }

    /* some error in UART */
    if( *c < 0 ) {
	*result = BRL1_LINK;
	return 0;
    }

    /* everything's fine */
    *result = BRL1_VALID;
    return 1;
}


/*
 * brl1_receive
 *
 * This function reads a Bedrock-L1 protocol packet into the l1sc_t
 * response buffer.
 *
 * The operation of this function can be expressed as a finite state
 * machine:
 *

START STATE			INPUT		TRANSITION
==========================================================
BRL1_IDLE (reset or error)	flag		BRL1_FLAG