text: /*
   * Device driver for the via ADB on (many) Mac II-class machines
   *
   * Based on the original ADB keyboard handler Copyright (c) 1997 Alan Cox
   * Also derived from code Copyright (C) 1996 Paul Mackerras.
   *
   * With various updates provided over the years by Michael Schmitz,
   * Guideo Koerber and others.
   *
   * Rewrite for Unified ADB by Joshua M. Thompson (funaho@jurai.org)
   *
   * 1999-08-02 (jmt) - Initial rewrite for Unified ADB.
   * 2000-03-29 Tony Mantler <tonym@mac.linux-m68k.org>
   * 				- Big overhaul, should actually work now.
   */
   
  #include <stdarg.h>
  #include <linux/types.h>
  #include <linux/errno.h>
  #include <linux/kernel.h>
  #include <linux/delay.h>
  #include <linux/sched.h>
  #include <linux/adb.h>
  #include <asm/macintosh.h>
  #include <asm/macints.h>
  #include <asm/machw.h>
  #include <asm/mac_via.h>
  #include <asm/io.h>
  #include <asm/system.h>
  #include <asm/init.h>
  
  static volatile unsigned char *via;
  
  /* VIA registers - spaced 0x200 bytes apart */
  #define RS		0x200		/* skip between registers */
  #define B		0		/* B-side data */
  #define A		RS		/* A-side data */
  #define DIRB		(2*RS)		/* B-side direction (1=output) */
  #define DIRA		(3*RS)		/* A-side direction (1=output) */
  #define T1CL		(4*RS)		/* Timer 1 ctr/latch (low 8 bits) */
  #define T1CH		(5*RS)		/* Timer 1 counter (high 8 bits) */
  #define T1LL		(6*RS)		/* Timer 1 latch (low 8 bits) */
  #define T1LH		(7*RS)		/* Timer 1 latch (high 8 bits) */
  #define T2CL		(8*RS)		/* Timer 2 ctr/latch (low 8 bits) */
  #define T2CH		(9*RS)		/* Timer 2 counter (high 8 bits) */
  #define SR		(10*RS)		/* Shift register */
  #define ACR		(11*RS)		/* Auxiliary control register */
  #define PCR		(12*RS)		/* Peripheral control register */
  #define IFR		(13*RS)		/* Interrupt flag register */
  #define IER		(14*RS)		/* Interrupt enable register */
  #define ANH		(15*RS)		/* A-side data, no handshake */
  
  /* Bits in B data register: all active low */
  #define TREQ		0x08		/* Transfer request (input) */
  #define TACK		0x10		/* Transfer acknowledge (output) */
  #define TIP		0x20		/* Transfer in progress (output) */
  #define ST_MASK		0x30		/* mask for selecting ADB state bits */
  
  /* Bits in ACR */
  #define SR_CTRL		0x1c		/* Shift register control bits */
  #define SR_EXT		0x0c		/* Shift on external clock */
  #define SR_OUT		0x10		/* Shift out if 1 */
  
  /* Bits in IFR and IER */
  #define IER_SET		0x80		/* set bits in IER */
  #define IER_CLR		0		/* clear bits in IER */
  #define SR_INT		0x04		/* Shift register full/empty */
  #define SR_DATA		0x08		/* Shift register data */
  #define SR_CLOCK	0x10		/* Shift register clock */
  
  /* ADB transaction states according to GMHW */
  #define ST_CMD		0x00		/* ADB state: command byte */
  #define ST_EVEN		0x10		/* ADB state: even data byte */
  #define ST_ODD		0x20		/* ADB state: odd data byte */
  #define ST_IDLE		0x30		/* ADB state: idle, nothing to send */
  
  static int  macii_init_via(void);
  static void macii_start(void);
  static void macii_interrupt(int irq, void *arg, struct pt_regs *regs);
  static void macii_retransmit(int);
  static void macii_queue_poll(void);
  
  static int macii_probe(void);
  static int macii_init(void);
  static int macii_send_request(struct adb_request *req, int sync);
  static int macii_write(struct adb_request *req);
  static int macii_autopoll(int devs);
  static void macii_poll(void);
  static int macii_reset_bus(void);
  
  struct adb_driver via_macii_driver = {
  	"Mac II",
  	macii_probe,
  	macii_init,
  	macii_send_request,
  	macii_autopoll,
  	macii_poll,
  	macii_reset_bus
  };
  
  static enum macii_state {
  	idle,
  	sending,
  	reading,
  	read_done,
  	awaiting_reply
  } macii_state;
  
  static int need_poll    = 0;
  static int command_byte = 0;
  static int last_reply   = 0;
  static int last_active  = 0;
  
  static struct adb_request *current_req;
  static struct adb_request *last_req;
  static struct adb_request *retry_req;
  static unsigned char reply_buf[16];
  static unsigned char *reply_ptr;
  static int reply_len;
  static int reading_reply;
  static int data_index;
  static int first_byte;
  static int prefix_len;
  static int status = ST_IDLE|TREQ;
  static int last_status;
  static int driver_running = 0;
  
  /* debug level 10 required for ADB logging (should be && debug_adb, ideally) */
  
  /* Check for MacII style ADB */
  static int macii_probe(void)
  {
  	if (macintosh_config->adb_type != MAC_ADB_II) return -ENODEV;
  
  	via = via1;
  
  	printk("adb: Mac II ADB Driver v1.0 for Unified ADB\n");
  	return 0;
  }
  
  /* Initialize the driver */
  int macii_init(void)
  {
  	unsigned long flags;
  	int err;
  	
  	save_flags(flags);
  	cli();
  	
  	err = macii_init_via();
  	if (err) return err;
  
  	err = request_irq(IRQ_MAC_ADB, macii_interrupt, IRQ_FLG_LOCK, "ADB",
  		    macii_interrupt);
  	if (err) return err;
  
  	macii_state = idle;
  	restore_flags(flags);	
  	return 0;
  }
  
  /* initialize the hardware */	
  static int macii_init_via(void)
  {
  	unsigned char x;
  
  	/* Set the lines up. We want TREQ as input TACK|TIP as output */
  	via[DIRB] = (via[DIRB] | TACK | TIP) & ~TREQ;
  
  	/* Set up state: idle */
  	via[B] |= ST_IDLE;
  	last_status = via[B] & (ST_MASK|TREQ);
  
  	/* Shift register on input */
  	via[ACR] = (via[ACR] & ~SR_CTRL) | SR_EXT;
  
  	/* Wipe any pending data and int */
  	x = via[SR];
  
  	return 0;
  }
  
  /* Send an ADB poll (Talk Register 0 command, tagged on the front of the request queue) */
  static void macii_queue_poll(void)
  {
  	static int device = 0;
  	static int in_poll=0;
  	static struct adb_request req;
  	unsigned long flags;
  	
  	if (in_poll) printk("macii_queue_poll: double poll!\n");
  
  	in_poll++;
  	if (++device > 15) device = 1;
  
  	adb_request(&req, NULL, ADBREQ_REPLY|ADBREQ_NOSEND, 1,
  		    ADB_READREG(device, 0));
  
  	save_flags(flags);
  	cli();
  
  	req.next = current_req;
  	current_req = &req;
  
  	restore_flags(flags);
  	macii_start();
  	in_poll--;
  }
  
  /* Send an ADB retransmit (Talk, appended to the request queue) */
  static void macii_retransmit(int device)
  {
  	static int in_retransmit = 0;
  	static struct adb_request rt;
  	unsigned long flags;
  	
  	if (in_retransmit) printk("macii_retransmit: double retransmit!\n");
  
  	in_retransmit++;
  
  	adb_request(&rt, NULL, ADBREQ_REPLY|ADBREQ_NOSEND, 1,
  		    ADB_READREG(device, 0));
  
  	save_flags(flags);
  	cli();
  
  	if (current_req != NULL) {
  		last_req->next = &rt;
  		last_req = &rt;
  	} else {
  		current_req = &rt;
  		last_req = &rt;
  	}
  
  	if (macii_state == idle) macii_start();
  
  	restore_flags(flags);
  	in_retransmit--;
  }
  
  /* Send an ADB request; if sync, poll out the reply 'till it's done */
  static int macii_send_request(struct adb_request *req, int sync)
  {
  	int i;
  
  	i = macii_write(req);
  	if (i) return i;
  
  	if (sync) {
  		while (!req->complete) macii_poll();
  	}
  	return 0;
  }
  
  /* Send an ADB request */
  static int macii_write(struct adb_request *req)
  {
  	unsigned long flags;
  
  	if (req->nbytes < 2 || req->data[0] != ADB_PACKET || req->nbytes > 15) {
  		req->complete = 1;
  		return -EINVAL;
  	}
  	
  	req->next = 0;
  	req->sent = 0;
  	req->complete = 0;
  	req->reply_len = 0;
  
  	save_flags(flags); cli();
  
  	if (current_req != NULL) {
  		last_req->next = req;
  		last_req = req;
  	} else {
  		current_req = req;
  		last_req = req;
  		if (macii_state == idle) macii_start();
  	}
  
  	restore_flags(flags);
  	return 0;
  }
  
  /* Start auto-polling */
  static int macii_autopoll(int devs)
  {
  	/* Just ping a random default address */
  	if (!(current_req || retry_req))
  		macii_retransmit( (last_active < 16 && last_active > 0) ? last_active : 3);
  	return 0;
  }
  
  /* Prod the chip without interrupts */
  static void macii_poll(void)
  {
  	unsigned long flags;
  
  	save_flags(flags); cli();
  	if (via[IFR] & SR_INT) macii_interrupt(0, 0, 0);
  	restore_flags(flags);
  }
  
  /* Reset the bus */
  static int macii_reset_bus(void)
  {
  	static struct adb_request req;
  	
  	/* Command = 0, Address = ignored */
  	adb_request(&req, NULL, 0, 1, ADB_BUSRESET);
  
  	return 0;
  }
  
  /* Start sending ADB packet */
  static void macii_start(void)
  {
  	unsigned long flags;
  	struct adb_request *req;
  
  	req = current_req;
  	if (!req) return;
  	
  	/* assert macii_state == idle */
  	if (macii_state != idle) {
  		printk("macii_start: called while driver busy (%p %x %x)!\n",
  			req, macii_state, (uint) via1[B] & (ST_MASK|TREQ));
  		return;
  	}
  
  	save_flags(flags); cli();
  	
  	/* 
  	 * IRQ signaled ?? (means ADB controller wants to send, or might 
  	 * be end of packet if we were reading)
  	 */
  	/*
  	 * 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 = sending;
  	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 sending:
  			req = current_req;
  			if (data_index >= req->nbytes) {
  				/* print an error message if a listen command has no data */
  				if (((command_byte & 0x0C) == 0x08)
  				 /* && (console_loglevel == 10) */
  				    && (data_index == 2))
  					printk("MacII ADB: 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 {
  				via[SR] = req->data[data_index++];
  
  				if ( (via[B] & ST_MASK) == ST_CMD ) {
  					/* just sent the command byte, set to EVEN */
  					via[B] = (via[B] & ~ST_MASK) | ST_EVEN;
  				} else {
  					/* 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 ADB: 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) == 0) && (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;
  			}
  			
  			/* set ADB state to idle */
  			via[B] = (via[B] & ~ST_MASK) | ST_IDLE;
  			
  			/* /IRQ seen, so the ADB controller has data for us */
  			if ((via[B] & TREQ) != 0) {
  				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);
  }
  