via-macii.c

Linux内核源代码 为压缩文件 是<<Linux内核>>一书中的源代码

		 *	won't be called again from send_request!
		 *	(need to re-check other cases ...)
		 */
		/*
		 * if the interrupt handler set the need_poll
		 * flag, it's hopefully a SRQ poll or re-Talk
		 * so we try to send here anyway
		 */
		if (!need_poll) {
			if (console_loglevel == 10)
				printk("macii_start: device busy - retry %p state %d status %x!\n", 
					req, macii_state,
					(uint) via[B] & (ST_MASK|TREQ));
			retry_req = req;
			/* set ADB status here ? */
			restore_flags(flags);
			return;
		} else {
			need_poll = 0;
		}
	}
	/*
	 * Another retry pending? (sanity check)
	 */
	if (retry_req) {
		retry_req = NULL;
	}

	/* Now send it. Be careful though, that first byte of the request */
	/* is actually ADB_PACKET; the real data begins at index 1!	  */

	/* store command byte */
	command_byte = req->data[1];
	/* Output mode */
	via[ACR] |= SR_OUT;
	/* Load data */
	via[SR] = req->data[1];
	/* set ADB state to 'command' */
	via[B] = (via[B] & ~ST_MASK) | ST_CMD;

	macii_state = sent_first_byte;
	data_index = 2;

	restore_flags(flags);
}

/*
 * The notorious ADB interrupt handler - does all of the protocol handling, 
 * except for starting new send operations. Relies heavily on the ADB 
 * controller sending and receiving data, thereby generating SR interrupts
 * for us. This means there has to be always activity on the ADB bus, otherwise
 * the whole process dies and has to be re-kicked by sending TALK requests ...
 * CUDA-based Macs seem to solve this with the autopoll option, for MacII-type
 * ADB the problem isn't solved yet (retransmit of the latest active TALK seems
 * a good choice; either on timeout or on a timer interrupt).
 *
 * The basic ADB state machine was left unchanged from the original MacII code
 * by Alan Cox, which was based on the CUDA driver for PowerMac. 
 * The syntax of the ADB status lines seems to be totally different on MacII, 
 * though. MacII uses the states Command -> Even -> Odd -> Even ->...-> Idle for
 * sending, and Idle -> Even -> Odd -> Even ->...-> Idle for receiving. Start 
 * and end of a receive packet are signaled by asserting /IRQ on the interrupt
 * line. Timeouts are signaled by a sequence of 4 0xFF, with /IRQ asserted on 
 * every other byte. SRQ is probably signaled by 3 or more 0xFF tacked on the 
 * end of a packet. (Thanks to Guido Koerber for eavesdropping on the ADB 
 * protocol with a logic analyzer!!)
 *
 * Note: As of 21/10/97, the MacII ADB part works including timeout detection
 * and retransmit (Talk to the last active device).
 */
void macii_interrupt(int irq, void *arg, struct pt_regs *regs)
{
	int x, adbdir;
	unsigned long flags;
	struct adb_request *req;

	last_status = status;

	/* prevent races due to SCSI enabling ints */
	save_flags(flags); cli();

	if (driver_running) {
		restore_flags(flags);
		return;
	}

	driver_running = 1;
	
	status = via[B] & (ST_MASK|TREQ);
	adbdir = via[ACR] & SR_OUT;

	switch (macii_state) {
		case idle:
			x = via[SR];
			first_byte = x;
			/* set ADB state = even for first data byte */
			via[B] = (via[B] & ~ST_MASK) | ST_EVEN;

			reply_buf[0] = first_byte; /* was command_byte?? */
			reply_ptr = reply_buf + 1;
			reply_len = 1;
			prefix_len = 1;
			reading_reply = 0;

			macii_state = reading;
			break;

		case awaiting_reply:
			/* handshake etc. for II ?? */
			x = via[SR];
			first_byte = x;
			/* set ADB state = even for first data byte */
			via[B] = (via[B] & ~ST_MASK) | ST_EVEN;

			current_req->reply[0] = first_byte;
			reply_ptr = current_req->reply + 1;
			reply_len = 1;
			prefix_len = 1;
			reading_reply = 1;

			macii_state = reading;			
			break;

		case sent_first_byte:
			req = current_req;
			/* maybe we're already done (Talk, or Poll)? */
			if (data_index >= req->nbytes) {
				/* reset to shift in */
				/* If it's a Listen command and we're done, someone's doing weird stuff. */
				if (((command_byte & 0x0C) == 0x08)
				    && (console_loglevel == 10))
					printk("macii_interrupt: listen command with no data: %x!\n", 
						command_byte);
				/* reset to shift in */
				via[ACR] &= ~SR_OUT;
				x = via[SR];
				/* set ADB state idle - might get SRQ */
				via[B] = (via[B] & ~ST_MASK) | ST_IDLE;

				req->sent = 1;

				if (req->reply_expected) {
					macii_state = awaiting_reply;
				} else {
					req->complete = 1;
					current_req = req->next;
					if (req->done) (*req->done)(req);
					macii_state = idle;
					if (current_req || retry_req)
						macii_start();
					else
						macii_retransmit((command_byte & 0xF0) >> 4);
				}
			} else {
				/* SR already set to shift out; send byte */
				via[SR] = current_req->data[data_index++];
				/* set state to ST_EVEN (first byte was: ST_CMD) */
				via[B] = (via[B] & ~ST_MASK) | ST_EVEN;
				macii_state = sending;
			}
			break;

		case sending:
			req = current_req;
			if (data_index >= req->nbytes) {
				/* reset to shift in */
				via[ACR] &= ~SR_OUT;
				x = via[SR];
				/* set ADB state idle - might get SRQ */
				via[B] = (via[B] & ~ST_MASK) | ST_IDLE;

				req->sent = 1;

				if (req->reply_expected) {
					macii_state = awaiting_reply;
				} else {
					req->complete = 1;
					current_req = req->next;
					if (req->done) (*req->done)(req);
					macii_state = idle;
					if (current_req || retry_req)
						macii_start();
					else
						macii_retransmit((command_byte & 0xF0) >> 4);
				}
			} else {
				via[SR] = req->data[data_index++];

				/* invert state bits, toggle ODD/EVEN */
				via[B] ^= ST_MASK;
			}
			break;

		case reading:

			/* timeout / SRQ handling for II hw */
			if( (first_byte == 0xFF && (reply_len-prefix_len)==2 
			     && memcmp(reply_ptr-2,"\xFF\xFF",2)==0) || 
			    ((reply_len-prefix_len)==3 
			     && memcmp(reply_ptr-3,"\xFF\xFF\xFF",3)==0))
			{
				/*
				 * possible timeout (in fact, most probably a 
				 * timeout, since SRQ can't be signaled without
				 * transfer on the bus).
				 * The last three bytes seen were FF, together 
				 * with the starting byte (in case we started
				 * on 'idle' or 'awaiting_reply') this probably
				 * makes four. So this is mostl likely #5!
				 * The timeout signal is a pattern 1 0 1 0 0..
				 * on /INT, meaning we missed it :-(
				 */
				x = via[SR];
				if (x != 0xFF) printk("macii_interrupt: mistaken timeout/SRQ!\n");

				if ((status & TREQ) == (last_status & TREQ)) {
					/* Not a timeout. Unsolicited SRQ? weird. */
					/* Terminate the SRQ packet and poll */
					need_poll = 1;
				}
				/* There's no packet to get, so reply is blank */
				via[B] ^= ST_MASK;
				reply_ptr -= (reply_len-prefix_len);
				reply_len = prefix_len;
				macii_state = read_done;
				break;
			} /* end timeout / SRQ handling for II hw. */

			if((reply_len-prefix_len)>3
				&& memcmp(reply_ptr-3,"\xFF\xFF\xFF",3)==0)
			{
				/* SRQ tacked on data packet */
				/* Terminate the packet (SRQ never ends) */
				x = via[SR];
				macii_state = read_done;
				reply_len -= 3;
				reply_ptr -= 3;
				need_poll = 1;
				/* need to continue; next byte not seen else */
			} else {
				/* Sanity check */
				if (reply_len > 15) reply_len = 0;
				/* read byte */
				x = via[SR];
				*reply_ptr = x;
				reply_ptr++;
				reply_len++;
			}
			/* The usual handshake ... */

			/*
			 * NetBSD hints that the next to last byte 
			 * is sent with IRQ !! 
			 * Guido found out it's the last one (0x0),
			 * but IRQ should be asserted already.
			 * Problem with timeout detection: First
			 * transition to /IRQ might be second 
			 * byte of timeout packet! 
			 * Timeouts are signaled by 4x FF.
			 */
			if (!(status & TREQ) && (x == 0x00)) { /* != 0xFF */
				/* invert state bits, toggle ODD/EVEN */
				via[B] ^= ST_MASK;

				/* adjust packet length */
				reply_len--;
				reply_ptr--;
				macii_state = read_done;
			} else {
				/* not caught: ST_CMD */
				/* required for re-entry 'reading'! */
				if ((status & ST_MASK) == ST_IDLE) {
					/* (in)sanity check - set even */
					via[B] = (via[B] & ~ST_MASK) | ST_EVEN;
				} else {
					/* invert state bits */
					via[B] ^= ST_MASK;
				}
			}
			break;

		case read_done:
			x = via[SR];
			if (reading_reply) {
				req = current_req;
				req->reply_len = reply_ptr - req->reply;
				req->complete = 1;
				current_req = req->next;
				if (req->done) (*req->done)(req);
			} else {
				adb_input(reply_buf, reply_ptr - reply_buf,
					  regs, 0);
			}

			/*
			 * remember this device ID; it's the latest we got a 
			 * reply from!
			 */
			last_reply = command_byte;
			last_active = (command_byte & 0xF0) >> 4;

			/* SRQ seen before, initiate poll now */
			if (need_poll) {
				macii_state = idle;
				macii_queue_poll();
				need_poll = 0;
				break;
			}

			/* /IRQ seen, so the ADB controller has data for us */
			if (!(status & TREQ)) {
				/* set ADB state to idle */
				via[B] = (via[B] & ~ST_MASK) | ST_IDLE;

				macii_state = reading;

				reply_buf[0] = command_byte;
				reply_ptr = reply_buf + 1;
				reply_len = 1;
				prefix_len = 1;
				reading_reply = 0;
			} else {
				/* no IRQ, send next packet or wait */
				macii_state = idle;
				if (current_req)
					macii_start();
				else
					macii_retransmit(last_active);
			}
			break;

		default:
		break;
	}
	/* reset mutex and interrupts */
	driver_running = 0;
	restore_flags(flags);
}