via.c

Go to the documentation of this file.

/*
 *  6522 Versatile Interface Adapter (VIA)
 *
 *  There are two of these on the Mac II. Some IRQs are vectored
 *  via them as are assorted bits and bobs - eg RTC, ADB.
 *
 * CSA: Motorola seems to have removed documentation on the 6522 from
 * their web site; try
 *     http://nerini.drf.com/vectrex/other/text/chips/6522/
 *     http://www.zymurgy.net/classic/vic20/vicdet1.htm
 * and
 *     http://193.23.168.87/mikro_laborversuche/via_iobaustein/via6522_1.html
 * for info.  A full-text web search on 6522 AND VIA will probably also
 * net some usefulness. <[email protected]> 20apr1999
 *
 * Additional data is here (the SY6522 was used in the Mac II etc):
 *     http://www.6502.org/documents/datasheets/synertek/synertek_sy6522.pdf
 *     http://www.6502.org/documents/datasheets/synertek/synertek_sy6522_programming_reference.pdf
 *
 * PRAM/RTC access algorithms are from the NetBSD RTC toolkit version 1.08b
 * by Erik Vogan and adapted to Linux by Joshua M. Thompson ([email protected])
 *
 */

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/irq.h>

#include <asm/bootinfo.h>
#include <asm/macintosh.h>
#include <asm/macints.h>
#include <asm/mac_via.h>
#include <asm/mac_psc.h>
#include <asm/mac_oss.h>

volatile __u8 *via1, *via2;
int rbv_present;
int via_alt_mapping;
EXPORT_SYMBOL(via_alt_mapping);
static __u8 rbv_clear;

/*
 * Globals for accessing the VIA chip registers without having to
 * check if we're hitting a real VIA or an RBV. Normally you could
 * just hit the combined register (ie, vIER|rIER) but that seems to
 * break on AV Macs...probably because they actually decode more than
 * eight address bits. Why can't Apple engineers at least be
 * _consistently_ lazy?                          - 1999-05-21 (jmt)
 */

static int gIER,gIFR,gBufA,gBufB;

/*
 * Timer defs.
 */

#define TICK_SIZE       10000
#define MAC_CLOCK_TICK      (783300/HZ)     /* ticks per HZ */
#define MAC_CLOCK_LOW       (MAC_CLOCK_TICK&0xFF)
#define MAC_CLOCK_HIGH      (MAC_CLOCK_TICK>>8)


/*
 * On Macs with a genuine VIA chip there is no way to mask an individual slot
 * interrupt. This limitation also seems to apply to VIA clone logic cores in
 * Quadra-like ASICs. (RBV and OSS machines don't have this limitation.)
 *
 * We used to fake it by configuring the relevent VIA pin as an output
 * (to mask the interrupt) or input (to unmask). That scheme did not work on
 * (at least) the Quadra 700. A NuBus card's /NMRQ signal is an open-collector
 * circuit (see Designing Cards and Drivers for Macintosh II and Macintosh SE,
 * p. 10-11 etc) but VIA outputs are not (see datasheet).
 *
 * Driving these outputs high must cause the VIA to source current and the
 * card to sink current when it asserts /NMRQ. Current will flow but the pin
 * voltage is uncertain and so the /NMRQ condition may still cause a transition
 * at the VIA2 CA1 input (which explains the lost interrupts). A side effect
 * is that a disabled slot IRQ can never be tested as pending or not.
 *
 * Driving these outputs low doesn't work either. All the slot /NMRQ lines are
 * (active low) OR'd together to generate the CA1 (aka "SLOTS") interrupt (see
 * The Guide To Macintosh Family Hardware, 2nd edition p. 167). If we drive a
 * disabled /NMRQ line low, the falling edge immediately triggers a CA1
 * interrupt and all slot interrupts after that will generate no transition
 * and therefore no interrupt, even after being re-enabled.
 *
 * So we make the VIA port A I/O lines inputs and use nubus_disabled to keep
 * track of their states. When any slot IRQ becomes disabled we mask the CA1
 * umbrella interrupt. Only when all slot IRQs become enabled do we unmask
 * the CA1 interrupt. It must remain enabled even when cards have no interrupt
 * handler registered. Drivers must therefore disable a slot interrupt at the
 * device before they call free_irq (like shared and autovector interrupts).
 *
 * There is also a related problem when MacOS is used to boot Linux. A network
 * card brought up by a MacOS driver may raise an interrupt while Linux boots.
 * This can be fatal since it can't be handled until the right driver loads
 * (if such a driver exists at all). Apparently related to this hardware
 * limitation, "Designing Cards and Drivers", p. 9-8, says that a slot
 * interrupt with no driver would crash MacOS (the book was written before
 * the appearance of Macs with RBV or OSS).
 */

static u8 nubus_disabled;

void via_debug_dump(void);

/*
 * Initialize the VIAs
 *
 * First we figure out where they actually _are_ as well as what type of
 * VIA we have for VIA2 (it could be a real VIA or an RBV or even an OSS.)
 * Then we pretty much clear them out and disable all IRQ sources.
 *
 * Note: the OSS is actually "detected" here and not in oss_init(). It just
 *   seems more logical to do it here since via_init() needs to know
 *   these things anyways.
 */

void __init via_init(void)
{
    switch(macintosh_config->via_type) {

        /* IIci, IIsi, IIvx, IIvi (P6xx), LC series */

        case MAC_VIA_IICI:
            via1 = (void *) VIA1_BASE;
            if (macintosh_config->ident == MAC_MODEL_IIFX) {
                via2 = NULL;
                rbv_present = 0;
                oss_present = 1;
            } else {
                via2 = (void *) RBV_BASE;
                rbv_present = 1;
                oss_present = 0;
            }
            if (macintosh_config->ident == MAC_MODEL_LCIII) {
                rbv_clear = 0x00;
            } else {
                /* on most RBVs (& unlike the VIAs), you   */
                /* need to set bit 7 when you write to IFR */
                /* in order for your clear to occur.       */
                rbv_clear = 0x80;
            }
            gIER = rIER;
            gIFR = rIFR;
            gBufA = rSIFR;
            gBufB = rBufB;
            break;

        /* Quadra and early MacIIs agree on the VIA locations */

        case MAC_VIA_QUADRA:
        case MAC_VIA_II:
            via1 = (void *) VIA1_BASE;
            via2 = (void *) VIA2_BASE;
            rbv_present = 0;
            oss_present = 0;
            rbv_clear = 0x00;
            gIER = vIER;
            gIFR = vIFR;
            gBufA = vBufA;
            gBufB = vBufB;
            break;
        default:
            panic("UNKNOWN VIA TYPE");
    }

    printk(KERN_INFO "VIA1 at %p is a 6522 or clone\n", via1);

    printk(KERN_INFO "VIA2 at %p is ", via2);
    if (rbv_present) {
        printk("an RBV\n");
    } else if (oss_present) {
        printk("an OSS\n");
    } else {
        printk("a 6522 or clone\n");
    }

#ifdef DEBUG_VIA
    via_debug_dump();
#endif

    /*
     * Shut down all IRQ sources, reset the timers, and
     * kill the timer latch on VIA1.
     */

    via1[vIER] = 0x7F;
    via1[vIFR] = 0x7F;
    via1[vT1LL] = 0;
    via1[vT1LH] = 0;
    via1[vT1CL] = 0;
    via1[vT1CH] = 0;
    via1[vT2CL] = 0;
    via1[vT2CH] = 0;
    via1[vACR] &= ~0xC0; /* setup T1 timer with no PB7 output */
    via1[vACR] &= ~0x03; /* disable port A & B latches */

    /*
     * SE/30: disable video IRQ
     * XXX: testing for SE/30 VBL
     */

    if (macintosh_config->ident == MAC_MODEL_SE30) {
        via1[vDirB] |= 0x40;
        via1[vBufB] |= 0x40;
    }

    /*
     * Set the RTC bits to a known state: all lines to outputs and
     * RTC disabled (yes that's 0 to enable and 1 to disable).
     */

    via1[vDirB] |= (VIA1B_vRTCEnb | VIA1B_vRTCClk | VIA1B_vRTCData);
    via1[vBufB] |= (VIA1B_vRTCEnb | VIA1B_vRTCClk);

    /* Everything below this point is VIA2/RBV only... */

    if (oss_present)
        return;

    if ((macintosh_config->via_type == MAC_VIA_QUADRA) &&
        (macintosh_config->adb_type != MAC_ADB_PB1) &&
        (macintosh_config->adb_type != MAC_ADB_PB2) &&
        (macintosh_config->ident    != MAC_MODEL_C660) &&
        (macintosh_config->ident    != MAC_MODEL_Q840)) {
        via_alt_mapping = 1;
        via1[vDirB] |= 0x40;
        via1[vBufB] &= ~0x40;
    } else {
        via_alt_mapping = 0;
    }

    /*
     * Now initialize VIA2. For RBV we just kill all interrupts;
     * for a regular VIA we also reset the timers and stuff.
     */

    via2[gIER] = 0x7F;
    via2[gIFR] = 0x7F | rbv_clear;
    if (!rbv_present) {
        via2[vT1LL] = 0;
        via2[vT1LH] = 0;
        via2[vT1CL] = 0;
        via2[vT1CH] = 0;
        via2[vT2CL] = 0;
        via2[vT2CH] = 0;
        via2[vACR] &= ~0xC0; /* setup T1 timer with no PB7 output */
        via2[vACR] &= ~0x03; /* disable port A & B latches */
    }

    /* Everything below this point is VIA2 only... */

    if (rbv_present)
        return;

    /*
     * Set vPCR for control line interrupts.
     *
     * CA1 (SLOTS IRQ), CB1 (ASC IRQ): negative edge trigger.
     *
     * Macs with ESP SCSI have a negative edge triggered SCSI interrupt.
     * Testing reveals that PowerBooks do too. However, the SE/30
     * schematic diagram shows an active high NCR5380 IRQ line.
     */

    pr_debug("VIA2 vPCR is 0x%02X\n", via2[vPCR]);
    if (macintosh_config->via_type == MAC_VIA_II) {
        /* CA2 (SCSI DRQ), CB2 (SCSI IRQ): indep. input, pos. edge */
        via2[vPCR] = 0x66;
    } else {
        /* CA2 (SCSI DRQ), CB2 (SCSI IRQ): indep. input, neg. edge */
        via2[vPCR] = 0x22;
    }
}

/*
 * Start the 100 Hz clock
 */

void __init via_init_clock(irq_handler_t func)
{
    via1[vACR] |= 0x40;
    via1[vT1LL] = MAC_CLOCK_LOW;
    via1[vT1LH] = MAC_CLOCK_HIGH;
    via1[vT1CL] = MAC_CLOCK_LOW;
    via1[vT1CH] = MAC_CLOCK_HIGH;

    if (request_irq(IRQ_MAC_TIMER_1, func, 0, "timer", func))
        pr_err("Couldn't register %s interrupt\n", "timer");
}

/*
 * Debugging dump, used in various places to see what's going on.
 */

void via_debug_dump(void)
{
    printk(KERN_DEBUG "VIA1: DDRA = 0x%02X DDRB = 0x%02X ACR = 0x%02X\n",
        (uint) via1[vDirA], (uint) via1[vDirB], (uint) via1[vACR]);
    printk(KERN_DEBUG "         PCR = 0x%02X  IFR = 0x%02X IER = 0x%02X\n",
        (uint) via1[vPCR], (uint) via1[vIFR], (uint) via1[vIER]);
    if (oss_present) {
        printk(KERN_DEBUG "VIA2: <OSS>\n");
    } else if (rbv_present) {
        printk(KERN_DEBUG "VIA2:  IFR = 0x%02X  IER = 0x%02X\n",
            (uint) via2[rIFR], (uint) via2[rIER]);
        printk(KERN_DEBUG "      SIFR = 0x%02X SIER = 0x%02X\n",
            (uint) via2[rSIFR], (uint) via2[rSIER]);
    } else {
        printk(KERN_DEBUG "VIA2: DDRA = 0x%02X DDRB = 0x%02X ACR = 0x%02X\n",
            (uint) via2[vDirA], (uint) via2[vDirB],
            (uint) via2[vACR]);
        printk(KERN_DEBUG "         PCR = 0x%02X  IFR = 0x%02X IER = 0x%02X\n",
            (uint) via2[vPCR],
            (uint) via2[vIFR], (uint) via2[vIER]);
    }
}

/*
 * This is always executed with interrupts disabled.
 *
 * TBI: get time offset between scheduling timer ticks
 */

unsigned long mac_gettimeoffset (void)
{
    unsigned long ticks, offset = 0;

    /* read VIA1 timer 2 current value */
    ticks = via1[vT1CL] | (via1[vT1CH] << 8);
    /* The probability of underflow is less than 2% */
    if (ticks > MAC_CLOCK_TICK - MAC_CLOCK_TICK / 50)
        /* Check for pending timer interrupt in VIA1 IFR */
        if (via1[vIFR] & 0x40) offset = TICK_SIZE;

    ticks = MAC_CLOCK_TICK - ticks;
    ticks = ticks * 10000L / MAC_CLOCK_TICK;

    return ticks + offset;
}

/*
 * Flush the L2 cache on Macs that have it by flipping
 * the system into 24-bit mode for an instant.
 */

void via_flush_cache(void)
{
    via2[gBufB] &= ~VIA2B_vMode32;
    via2[gBufB] |= VIA2B_vMode32;
}

/*
 * Return the status of the L2 cache on a IIci
 */

int via_get_cache_disable(void)
{
    /* Safeguard against being called accidentally */
    if (!via2) {
        printk(KERN_ERR "via_get_cache_disable called on a non-VIA machine!\n");
        return 1;
    }

    return (int) via2[gBufB] & VIA2B_vCDis;
}

/*
 * Initialize VIA2 for Nubus access
 */

void __init via_nubus_init(void)
{
    /* unlock nubus transactions */

    if ((macintosh_config->adb_type != MAC_ADB_PB1) &&
        (macintosh_config->adb_type != MAC_ADB_PB2)) {
        /* set the line to be an output on non-RBV machines */
        if (!rbv_present)
            via2[vDirB] |= 0x02;

        /* this seems to be an ADB bit on PMU machines */
        /* according to MkLinux.  -- jmt               */
        via2[gBufB] |= 0x02;
    }

    /*
     * Disable the slot interrupts. On some hardware that's not possible.
     * On some hardware it's unclear what all of these I/O lines do.
     */

    switch (macintosh_config->via_type) {
    case MAC_VIA_II:
    case MAC_VIA_QUADRA:
        pr_debug("VIA2 vDirA is 0x%02X\n", via2[vDirA]);
        break;
    case MAC_VIA_IICI:
        /* RBV. Disable all the slot interrupts. SIER works like IER. */
        via2[rSIER] = 0x7F;
        break;
    }
}

void via_nubus_irq_startup(int irq)
{
    int irq_idx = IRQ_IDX(irq);

    switch (macintosh_config->via_type) {
    case MAC_VIA_II:
    case MAC_VIA_QUADRA:
        /* Make the port A line an input. Probably redundant. */
        if (macintosh_config->via_type == MAC_VIA_II) {
            /* The top two bits are RAM size outputs. */
            via2[vDirA] &= 0xC0 | ~(1 << irq_idx);
        } else {
            /* Allow NuBus slots 9 through F. */
            via2[vDirA] &= 0x80 | ~(1 << irq_idx);
        }
        /* fall through */
    case MAC_VIA_IICI:
        via_irq_enable(irq);
        break;
    }
}

void via_nubus_irq_shutdown(int irq)
{
    switch (macintosh_config->via_type) {
    case MAC_VIA_II:
    case MAC_VIA_QUADRA:
        /* Ensure that the umbrella CA1 interrupt remains enabled. */
        via_irq_enable(irq);
        break;
    case MAC_VIA_IICI:
        via_irq_disable(irq);
        break;
    }
}

/*
 * The generic VIA interrupt routines (shamelessly stolen from Alan Cox's
 * via6522.c :-), disable/pending masks added.
 */

void via1_irq(unsigned int irq, struct irq_desc *desc)
{
    int irq_num;
    unsigned char irq_bit, events;

    events = via1[vIFR] & via1[vIER] & 0x7F;
    if (!events)
        return;

    irq_num = VIA1_SOURCE_BASE;
    irq_bit = 1;
    do {
        if (events & irq_bit) {
            via1[vIFR] = irq_bit;
            generic_handle_irq(irq_num);
        }
        ++irq_num;
        irq_bit <<= 1;
    } while (events >= irq_bit);
}

static void via2_irq(unsigned int irq, struct irq_desc *desc)
{
    int irq_num;
    unsigned char irq_bit, events;

    events = via2[gIFR] & via2[gIER] & 0x7F;
    if (!events)
        return;

    irq_num = VIA2_SOURCE_BASE;
    irq_bit = 1;
    do {
        if (events & irq_bit) {
            via2[gIFR] = irq_bit | rbv_clear;
            generic_handle_irq(irq_num);
        }
        ++irq_num;
        irq_bit <<= 1;
    } while (events >= irq_bit);
}

/*
 * Dispatch Nubus interrupts. We are called as a secondary dispatch by the
 * VIA2 dispatcher as a fast interrupt handler.
 */

void via_nubus_irq(unsigned int irq, struct irq_desc *desc)
{
    int slot_irq;
    unsigned char slot_bit, events;

    events = ~via2[gBufA] & 0x7F;
    if (rbv_present)
        events &= via2[rSIER];
    else
        events &= ~via2[vDirA];
    if (!events)
        return;

    do {
        slot_irq = IRQ_NUBUS_F;
        slot_bit = 0x40;
        do {
            if (events & slot_bit) {
                events &= ~slot_bit;
                generic_handle_irq(slot_irq);
            }
            --slot_irq;
            slot_bit >>= 1;
        } while (events);

        /* clear the CA1 interrupt and make certain there's no more. */
        via2[gIFR] = 0x02 | rbv_clear;
        events = ~via2[gBufA] & 0x7F;
        if (rbv_present)
            events &= via2[rSIER];
        else
            events &= ~via2[vDirA];
    } while (events);
}

/*
 * Register the interrupt dispatchers for VIA or RBV machines only.
 */

void __init via_register_interrupts(void)
{
    if (via_alt_mapping) {
        /* software interrupt */
        irq_set_chained_handler(IRQ_AUTO_1, via1_irq);
        /* via1 interrupt */
        irq_set_chained_handler(IRQ_AUTO_6, via1_irq);
    } else {
        irq_set_chained_handler(IRQ_AUTO_1, via1_irq);
    }
    irq_set_chained_handler(IRQ_AUTO_2, via2_irq);
    irq_set_chained_handler(IRQ_MAC_NUBUS, via_nubus_irq);
}

void via_irq_enable(int irq) {
    int irq_src = IRQ_SRC(irq);
    int irq_idx = IRQ_IDX(irq);

#ifdef DEBUG_IRQUSE
    printk(KERN_DEBUG "via_irq_enable(%d)\n", irq);
#endif

    if (irq_src == 1) {
        via1[vIER] = IER_SET_BIT(irq_idx);
    } else if (irq_src == 2) {
        if (irq != IRQ_MAC_NUBUS || nubus_disabled == 0)
            via2[gIER] = IER_SET_BIT(irq_idx);
    } else if (irq_src == 7) {
        switch (macintosh_config->via_type) {
        case MAC_VIA_II:
        case MAC_VIA_QUADRA:
            nubus_disabled &= ~(1 << irq_idx);
            /* Enable the CA1 interrupt when no slot is disabled. */
            if (!nubus_disabled)
                via2[gIER] = IER_SET_BIT(1);
            break;
        case MAC_VIA_IICI:
            /* On RBV, enable the slot interrupt.
             * SIER works like IER.
             */
            via2[rSIER] = IER_SET_BIT(irq_idx);
            break;
        }
    }
}

void via_irq_disable(int irq) {
    int irq_src = IRQ_SRC(irq);
    int irq_idx = IRQ_IDX(irq);

#ifdef DEBUG_IRQUSE
    printk(KERN_DEBUG "via_irq_disable(%d)\n", irq);
#endif

    if (irq_src == 1) {
        via1[vIER] = IER_CLR_BIT(irq_idx);
    } else if (irq_src == 2) {
        via2[gIER] = IER_CLR_BIT(irq_idx);
    } else if (irq_src == 7) {
        switch (macintosh_config->via_type) {
        case MAC_VIA_II:
        case MAC_VIA_QUADRA:
            nubus_disabled |= 1 << irq_idx;
            if (nubus_disabled)
                via2[gIER] = IER_CLR_BIT(1);
            break;
        case MAC_VIA_IICI:
            via2[rSIER] = IER_CLR_BIT(irq_idx);
            break;
        }
    }
}

void via1_set_head(int head)
{
    if (head == 0)
        via1[vBufA] &= ~VIA1A_vHeadSel;
    else
        via1[vBufA] |= VIA1A_vHeadSel;
}
EXPORT_SYMBOL(via1_set_head);

int via2_scsi_drq_pending(void)
{
    return via2[gIFR] & (1 << IRQ_IDX(IRQ_MAC_SCSIDRQ));
}
EXPORT_SYMBOL(via2_scsi_drq_pending);