via-macii.c

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/*
 * 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 ([email protected])
 *
 * 1999-08-02 (jmt) - Initial rewrite for Unified ADB.
 * 2000-03-29 Tony Mantler <[email protected]>
 *              - Big overhaul, should actually work now.
 * 2006-12-31 Finn Thain <[email protected]> - Another overhaul.
 *
 * Suggested reading:
 *   Inside Macintosh, ch. 5 ADB Manager
 *   Guide to the Macinstosh Family Hardware, ch. 8 Apple Desktop Bus
 *   Rockwell R6522 VIA datasheet
 *
 * Apple's "ADB Analyzer" bus sniffer is invaluable:
 *   ftp://ftp.apple.com/developer/Tool_Chest/Devices_-_Hardware/Apple_Desktop_Bus/
 */
 
#include <stdarg.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/adb.h>
#include <linux/interrupt.h>
#include <linux/init.h>
#include <asm/macintosh.h>
#include <asm/macints.h>
#include <asm/mac_via.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 CTLR_IRQ    0x08        /* Controller rcv status (input) */
#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 */

/* 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 irqreturn_t macii_interrupt(int irq, void *arg);
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,
} macii_state;

static struct adb_request *current_req; /* first request struct in the queue */
static struct adb_request *last_req;     /* last request struct in the queue */
static unsigned char reply_buf[16];        /* storage for autopolled replies */
static unsigned char *reply_ptr;     /* next byte in reply_buf or req->reply */
static int reading_reply;        /* store reply in reply_buf else req->reply */
static int data_index;      /* index of the next byte to send from req->data */
static int reply_len; /* number of bytes received in reply_buf or req->reply */
static int status;          /* VIA's ADB status bits captured upon interrupt */
static int last_status;              /* status bits as at previous interrupt */
static int srq_asserted;     /* have to poll for the device that asserted it */
static int command_byte;         /* the most recent command byte transmitted */
static int autopoll_devs;      /* bits set are device addresses to be polled */

/* Sanity check for request queue. Doesn't check for cycles. */
static int request_is_queued(struct adb_request *req) {
    struct adb_request *cur;
    unsigned long flags;
    local_irq_save(flags);
    cur = current_req;
    while (cur) {
        if (cur == req) {
            local_irq_restore(flags);
            return 1;
        }
        cur = cur->next;
    }
    local_irq_restore(flags);
    return 0;
}

/* 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;
    
    local_irq_save(flags);
    
    err = macii_init_via();
    if (err) goto out;

    err = request_irq(IRQ_MAC_ADB, macii_interrupt, 0, "ADB",
              macii_interrupt);
    if (err) goto out;

    macii_state = idle;
out:
    local_irq_restore(flags);
    return err;
}

/* initialize the hardware */   
static int macii_init_via(void)
{
    unsigned char x;

    /* We want CTLR_IRQ as input and ST_EVEN | ST_ODD as output lines. */
    via[DIRB] = (via[DIRB] | ST_EVEN | ST_ODD) & ~CTLR_IRQ;

    /* Set up state: idle */
    via[B] |= ST_IDLE;
    last_status = via[B] & (ST_MASK|CTLR_IRQ);

    /* 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 prepended to the request queue) */
static void macii_queue_poll(void)
{
    /* No point polling the active device as it will never assert SRQ, so
     * poll the next device in the autopoll list. This could leave us
     * stuck in a polling loop if an unprobed device is asserting SRQ.
     * In theory, that could only happen if a device was plugged in after
     * probing started. Unplugging it again will break the cycle.
     * (Simply polling the next higher device often ends up polling almost
     * every device (after wrapping around), which takes too long.)
     */
    int device_mask;
    int next_device;
    static struct adb_request req;

    if (!autopoll_devs) return;

    device_mask = (1 << (((command_byte & 0xF0) >> 4) + 1)) - 1;
    if (autopoll_devs & ~device_mask)
        next_device = ffs(autopoll_devs & ~device_mask) - 1;
    else
        next_device = ffs(autopoll_devs) - 1;

    BUG_ON(request_is_queued(&req));

    adb_request(&req, NULL, ADBREQ_NOSEND, 1,
                ADB_READREG(next_device, 0));

    req.sent = 0;
    req.complete = 0;
    req.reply_len = 0;
    req.next = current_req;

    if (current_req != NULL) {
        current_req = &req;
    } else {
        current_req = &req;
        last_req = &req;
    }
}

/* 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 err;
    unsigned long flags;

    BUG_ON(request_is_queued(req));

    local_irq_save(flags);
    err = macii_write(req);
    local_irq_restore(flags);

    if (!err && sync) {
        while (!req->complete) {
            macii_poll();
        }
        BUG_ON(request_is_queued(req));
    }

    return err;
}

/* Send an ADB request (append to request queue) */
static int macii_write(struct adb_request *req)
{
    if (req->nbytes < 2 || req->data[0] != ADB_PACKET || req->nbytes > 15) {
        req->complete = 1;
        return -EINVAL;
    }
    
    req->next = NULL;
    req->sent = 0;
    req->complete = 0;
    req->reply_len = 0;

    if (current_req != NULL) {
        last_req->next = req;
        last_req = req;
    } else {
        current_req = req;
        last_req = req;
        if (macii_state == idle) macii_start();
    }
    return 0;
}

/* Start auto-polling */
static int macii_autopoll(int devs)
{
    static struct adb_request req;
    unsigned long flags;
    int err = 0;

    /* bit 1 == device 1, and so on. */
    autopoll_devs = devs & 0xFFFE;

    if (!autopoll_devs) return 0;

    local_irq_save(flags);

    if (current_req == NULL) {
        /* Send a Talk Reg 0. The controller will repeatedly transmit
         * this as long as it is idle.
         */
        adb_request(&req, NULL, ADBREQ_NOSEND, 1,
                    ADB_READREG(ffs(autopoll_devs) - 1, 0));
        err = macii_write(&req);
    }

    local_irq_restore(flags);
    return err;
}

static inline int need_autopoll(void) {
    /* Was the last command Talk Reg 0
     * and is the target on the autopoll list?
     */
    if ((command_byte & 0x0F) == 0x0C &&
        ((1 << ((command_byte & 0xF0) >> 4)) & autopoll_devs))
        return 0;
    return 1;
}

/* Prod the chip without interrupts */
static void macii_poll(void)
{
    disable_irq(IRQ_MAC_ADB);
    macii_interrupt(0, NULL);
    enable_irq(IRQ_MAC_ADB);
}

/* Reset the bus */
static int macii_reset_bus(void)
{
    static struct adb_request req;
    
    if (request_is_queued(&req))
        return 0;

    /* Command = 0, Address = ignored */
    adb_request(&req, NULL, 0, 1, ADB_BUSRESET);

    /* Don't want any more requests during the Global Reset low time. */
    udelay(3000);

    return 0;
}

/* Start sending ADB packet */
static void macii_start(void)
{
    struct adb_request *req;

    req = current_req;

    BUG_ON(req == NULL);

    BUG_ON(macii_state != idle);

    /* Now send it. Be careful though, that first byte of the request
     * is actually ADB_PACKET; the real data begins at index 1!
     * And req->nbytes is the number of bytes of real data plus one.
     */

    /* 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;
}

/*
 * The notorious ADB interrupt handler - does all of the protocol handling.
 * Relies on the ADB controller sending and receiving data, thereby
 * generating shift register interrupts (SR_INT) for us. This means there has
 * to be activity on the ADB bus. The chip will poll to achieve this.
 *
 * 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 is 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 signalled by asserting /IRQ on the
 * interrupt line (/IRQ means the CTLR_IRQ bit in port B; not to be confused
 * with the VIA shift register interrupt. /IRQ never actually interrupts the
 * processor, it's just an ordinary input.)
 */
static irqreturn_t macii_interrupt(int irq, void *arg)
{
    int x;
    static int entered;
    struct adb_request *req;

    if (!arg) {
        /* Clear the SR IRQ flag when polling. */
        if (via[IFR] & SR_INT)
            via[IFR] = SR_INT;
        else
            return IRQ_NONE;
    }

    BUG_ON(entered++);

    last_status = status;
    status = via[B] & (ST_MASK|CTLR_IRQ);

    switch (macii_state) {
        case idle:
            if (reading_reply) {
                reply_ptr = current_req->reply;
            } else {
                BUG_ON(current_req != NULL);
                reply_ptr = reply_buf;
            }

            x = via[SR];

            if ((status & CTLR_IRQ) && (x == 0xFF)) {
                /* Bus timeout without SRQ sequence:
                 *     data is "FF" while CTLR_IRQ is "H"
                 */
                reply_len = 0;
                srq_asserted = 0;
                macii_state = read_done;
            } else {
                macii_state = reading;
                *reply_ptr = x;
                reply_len = 1;
            }

            /* set ADB state = even for first data byte */
            via[B] = (via[B] & ~ST_MASK) | ST_EVEN;
            break;

        case sending:
            req = current_req;
            if (data_index >= req->nbytes) {
                req->sent = 1;
                macii_state = idle;

                if (req->reply_expected) {
                    reading_reply = 1;
                } else {
                    req->complete = 1;
                    current_req = req->next;
                    if (req->done) (*req->done)(req);

                    if (current_req)
                        macii_start();
                    else
                        if (need_autopoll())
                            macii_autopoll(autopoll_devs);
                }

                if (macii_state == idle) {
                    /* 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;
                }
            } 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:
            x = via[SR];
            BUG_ON((status & ST_MASK) == ST_CMD ||
                   (status & ST_MASK) == ST_IDLE);

            /* Bus timeout with SRQ sequence:
             *     data is "XX FF"      while CTLR_IRQ is "L L"
             * End of packet without SRQ sequence:
             *     data is "XX...YY 00" while CTLR_IRQ is "L...H L"
             * End of packet SRQ sequence:
             *     data is "XX...YY 00" while CTLR_IRQ is "L...L L"
             * (where XX is the first response byte and
             * YY is the last byte of valid response data.)
             */

            srq_asserted = 0;
            if (!(status & CTLR_IRQ)) {
                if (x == 0xFF) {
                    if (!(last_status & CTLR_IRQ)) {
                        macii_state = read_done;
                        reply_len = 0;
                        srq_asserted = 1;
                    }
                } else if (x == 0x00) {
                    macii_state = read_done;
                    if (!(last_status & CTLR_IRQ))
                        srq_asserted = 1;
                }
            }

            if (macii_state == reading) {
                BUG_ON(reply_len > 15);
                reply_ptr++;
                *reply_ptr = x;
                reply_len++;
            }

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

        case read_done:
            x = via[SR];

            if (reading_reply) {
                reading_reply = 0;
                req = current_req;
                req->reply_len = reply_len;
                req->complete = 1;
                current_req = req->next;
                if (req->done) (*req->done)(req);
            } else if (reply_len && autopoll_devs)
                adb_input(reply_buf, reply_len, 0);

            macii_state = idle;

            /* SRQ seen before, initiate poll now */
            if (srq_asserted)
                macii_queue_poll();

            if (current_req)
                macii_start();
            else
                if (need_autopoll())
                    macii_autopoll(autopoll_devs);

            if (macii_state == idle)
                via[B] = (via[B] & ~ST_MASK) | ST_IDLE;
            break;

        default:
        break;
    }

    entered--;
    return IRQ_HANDLED;
}