// SPDX-License-Identifier: GPL-2.0
/*
 *      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. <cananian@alumni.princeton.edu> 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 (funaho@jurai.org)
 *
 */

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

#include "mac.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;

/*
 * 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 relevant 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);
static void via_nubus_init(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.
 */

void __init via_init(void)
{
        via1 = (void *)VIA1_BASE;
        pr_debug("VIA1 detected at %p\n", via1);

        if (oss_present) {
                via2 = NULL;
                rbv_present = 0;
        } else {
                switch (macintosh_config->via_type) {

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

                case MAC_VIA_IICI:
                        via2 = (void *)RBV_BASE;
                        pr_debug("VIA2 (RBV) detected at %p\n", via2);
                        rbv_present = 1;
                        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:
                        via2 = (void *) VIA2_BASE;
                        pr_debug("VIA2 detected at %p\n", via2);
                        rbv_present = 0;
                        rbv_clear = 0x00;
                        gIER = vIER;
                        gIFR = vIFR;
                        gBufA = vBufA;
                        gBufB = vBufB;
                        break;

                default:
                        panic("UNKNOWN VIA TYPE");
                }
        }

#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[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
         */

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

        switch (macintosh_config->adb_type) {
        case MAC_ADB_IOP:
        case MAC_ADB_II:
        case MAC_ADB_PB1:
                /*
                 * 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;
                break;
        }

        /* 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[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 */
        }

        via_nubus_init();

        /* 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;
        }
}

/*
 * 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 (!via2)
                return;
        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]);
        }
}

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

void via_l2_flush(int writeback)
{
        unsigned long flags;

        local_irq_save(flags);
        via2[gBufB] &= ~VIA2B_vMode32;
        via2[gBufB] |= VIA2B_vMode32;
        local_irq_restore(flags);
}

/*
 * Initialize VIA2 for Nubus access
 */

static 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);
                }
                fallthrough;
        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.
 */

#define VIA_TIMER_1_INT BIT(6)

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

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

        irq_num = IRQ_MAC_TIMER_1;
        irq_bit = VIA_TIMER_1_INT;
        if (events & irq_bit) {
                unsigned long flags;

                local_irq_save(flags);
                via1[vIFR] = irq_bit;
                generic_handle_irq(irq_num);
                local_irq_restore(flags);

                events &= ~irq_bit;
                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(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.
 */

static void via_nubus_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);

        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);

        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);

/* timer and clock source */

#define VIA_CLOCK_FREQ     783360                /* VIA "phase 2" clock in Hz */
#define VIA_TIMER_CYCLES   (VIA_CLOCK_FREQ / HZ) /* clock cycles per jiffy */

#define VIA_TC             (VIA_TIMER_CYCLES - 2) /* including 0 and -1 */
#define VIA_TC_LOW         (VIA_TC & 0xFF)
#define VIA_TC_HIGH        (VIA_TC >> 8)

static u64 mac_read_clk(struct clocksource *cs);

static struct clocksource mac_clk = {
        .name   = "via1",
        .rating = 250,
        .read   = mac_read_clk,
        .mask   = CLOCKSOURCE_MASK(32),
        .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
};

static u32 clk_total, clk_offset;

static irqreturn_t via_timer_handler(int irq, void *dev_id)
{
        clk_total += VIA_TIMER_CYCLES;
        clk_offset = 0;
        legacy_timer_tick(1);

        return IRQ_HANDLED;
}

void __init via_init_clock(void)
{
        if (request_irq(IRQ_MAC_TIMER_1, via_timer_handler, IRQF_TIMER, "timer",
                        NULL)) {
                pr_err("Couldn't register %s interrupt\n", "timer");
                return;
        }

        via1[vT1CL] = VIA_TC_LOW;
        via1[vT1CH] = VIA_TC_HIGH;
        via1[vACR] |= 0x40;

        clocksource_register_hz(&mac_clk, VIA_CLOCK_FREQ);
}

static u64 mac_read_clk(struct clocksource *cs)
{
        unsigned long flags;
        u8 count_high;
        u16 count;
        u32 ticks;

        /*
         * Timer counter wrap-around is detected with the timer interrupt flag
         * but reading the counter low byte (vT1CL) would reset the flag.
         * Also, accessing both counter registers is essentially a data race.
         * These problems are avoided by ignoring the low byte. Clock accuracy
         * is 256 times worse (error can reach 0.327 ms) but CPU overhead is
         * reduced by avoiding slow VIA register accesses.
         *
         * The VIA timer counter observably decrements to 0xFFFF before the
         * counter reload interrupt gets raised. That complicates things a bit.
         *
         * State | vT1CH      | VIA_TIMER_1_INT | inference drawn
         * ------+------------+-----------------+-----------------------------
         * i     | FE thru 00 | false           | counter is decrementing
         * ii    | FF         | false           | counter wrapped
         * iii   | FF         | true            | wrapped, interrupt raised
         * iv    | FF         | false           | wrapped, interrupt handled
         * v     | FE thru 00 | true            | wrapped, interrupt unhandled
         *
         * State iv is never observed because handling the interrupt involves
         * a 6522 register access and every access consumes a "phi 2" clock
         * cycle. So 0xFF implies either state ii or state iii, depending on
         * the value of the VIA_TIMER_1_INT bit.
         */

        local_irq_save(flags);
        count_high = via1[vT1CH];
        if (count_high == 0xFF)
                count_high = 0;
        if (count_high > 0 && (via1[vIFR] & VIA_TIMER_1_INT))
                clk_offset = VIA_TIMER_CYCLES;
        count = count_high << 8;
        ticks = VIA_TIMER_CYCLES - count;
        ticks += clk_offset + clk_total;
        local_irq_restore(flags);

        return ticks;
}