/*
 * 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 <linux/init.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>

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)
         */
#if 0 /* FIXME: This is broke broke broke, for some reason */
        if ((via[B] & TREQ) == 0) {
                printk("macii_start: weird poll stuff. huh?\n");
                /*
                 *      FIXME - we need to restart this on a timer
                 *      or a collision at boot hangs us.
                 *      Never set macii_state to idle here, or macii_start 
                 *      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;
                }
        }
#endif
        /*
         * 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);
}