/*
 *      Operating System Services (OSS) chip handling
 *      Written by Joshua M. Thompson (funaho@jurai.org)
 *
 *
 *      This chip is used in the IIfx in place of VIA #2. It acts like a fancy
 *      VIA chip with prorammable interrupt levels.
 *
 * 990502 (jmt) - Major rewrite for new interrupt architecture as well as some
 *                recent insights into OSS operational details.
 * 990610 (jmt) - Now taking full advantage of the OSS. Interrupts are mapped
 *                to mostly match the A/UX interrupt scheme supported on the
 *                VIA side. Also added support for enabling the ISM irq again
 *                since we now have a functional IOP manager.
 */

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

int oss_present;
volatile struct mac_oss *oss;

/*
 * Initialize the OSS
 *
 * The OSS "detection" code is actually in via_init() which is always called
 * before us. Thus we can count on oss_present being valid on entry.
 */

void __init oss_init(void)
{
        int i;

        if (!oss_present) return;

        oss = (struct mac_oss *) OSS_BASE;

        /* Disable all interrupts. Unlike a VIA it looks like we    */
        /* do this by setting the source's interrupt level to zero. */

        for (i = 0; i <= OSS_NUM_SOURCES; i++) {
                oss->irq_level[i] = 0;
        }
}

/*
 * Initialize OSS for Nubus access
 */

void __init oss_nubus_init(void)
{
}

/*
 * Handle miscellaneous OSS interrupts.
 */

static void oss_irq(unsigned int irq, struct irq_desc *desc)
{
        int events = oss->irq_pending &
                     (OSS_IP_IOPSCC | OSS_IP_SCSI | OSS_IP_IOPISM);

#ifdef DEBUG_IRQS
        if ((console_loglevel == 10) && !(events & OSS_IP_SCSI)) {
                printk("oss_irq: irq %u events = 0x%04X\n", irq,
                        (int) oss->irq_pending);
        }
#endif

        if (events & OSS_IP_IOPSCC) {
                oss->irq_pending &= ~OSS_IP_IOPSCC;
                generic_handle_irq(IRQ_MAC_SCC);
        }

        if (events & OSS_IP_SCSI) {
                oss->irq_pending &= ~OSS_IP_SCSI;
                generic_handle_irq(IRQ_MAC_SCSI);
        }

        if (events & OSS_IP_IOPISM) {
                oss->irq_pending &= ~OSS_IP_IOPISM;
                generic_handle_irq(IRQ_MAC_ADB);
        }
}

/*
 * Nubus IRQ handler, OSS style
 *
 * Unlike the VIA/RBV this is on its own autovector interrupt level.
 */

static void oss_nubus_irq(unsigned int irq, struct irq_desc *desc)
{
        int events, irq_bit, i;

        events = oss->irq_pending & OSS_IP_NUBUS;
        if (!events)
                return;

#ifdef DEBUG_NUBUS_INT
        if (console_loglevel > 7) {
                printk("oss_nubus_irq: events = 0x%04X\n", events);
        }
#endif
        /* There are only six slots on the OSS, not seven */

        i = 6;
        irq_bit = 0x40;
        do {
                --i;
                irq_bit >>= 1;
                if (events & irq_bit) {
                        oss->irq_pending &= ~irq_bit;
                        generic_handle_irq(NUBUS_SOURCE_BASE + i);
                }
        } while(events & (irq_bit - 1));
}

/*
 * Register the OSS and NuBus interrupt dispatchers.
 *
 * This IRQ mapping is laid out with two things in mind: first, we try to keep
 * things on their own levels to avoid having to do double-dispatches. Second,
 * the levels match as closely as possible the alternate IRQ mapping mode (aka
 * "A/UX mode") available on some VIA machines.
 */

#define OSS_IRQLEV_IOPISM    IRQ_AUTO_1
#define OSS_IRQLEV_SCSI      IRQ_AUTO_2
#define OSS_IRQLEV_NUBUS     IRQ_AUTO_3
#define OSS_IRQLEV_IOPSCC    IRQ_AUTO_4
#define OSS_IRQLEV_VIA1      IRQ_AUTO_6

void __init oss_register_interrupts(void)
{
        irq_set_chained_handler(OSS_IRQLEV_IOPISM, oss_irq);
        irq_set_chained_handler(OSS_IRQLEV_SCSI,   oss_irq);
        irq_set_chained_handler(OSS_IRQLEV_NUBUS,  oss_nubus_irq);
        irq_set_chained_handler(OSS_IRQLEV_IOPSCC, oss_irq);
        irq_set_chained_handler(OSS_IRQLEV_VIA1,   via1_irq);

        /* OSS_VIA1 gets enabled here because it has no machspec interrupt. */
        oss->irq_level[OSS_VIA1] = IRQ_AUTO_6;
}

/*
 * Enable an OSS interrupt
 *
 * It looks messy but it's rather straightforward. The switch() statement
 * just maps the machspec interrupt numbers to the right OSS interrupt
 * source (if the OSS handles that interrupt) and then sets the interrupt
 * level for that source to nonzero, thus enabling the interrupt.
 */

void oss_irq_enable(int irq) {
#ifdef DEBUG_IRQUSE
        printk("oss_irq_enable(%d)\n", irq);
#endif
        switch(irq) {
                case IRQ_MAC_SCC:
                        oss->irq_level[OSS_IOPSCC] = OSS_IRQLEV_IOPSCC;
                        return;
                case IRQ_MAC_ADB:
                        oss->irq_level[OSS_IOPISM] = OSS_IRQLEV_IOPISM;
                        return;
                case IRQ_MAC_SCSI:
                        oss->irq_level[OSS_SCSI] = OSS_IRQLEV_SCSI;
                        return;
                case IRQ_NUBUS_9:
                case IRQ_NUBUS_A:
                case IRQ_NUBUS_B:
                case IRQ_NUBUS_C:
                case IRQ_NUBUS_D:
                case IRQ_NUBUS_E:
                        irq -= NUBUS_SOURCE_BASE;
                        oss->irq_level[irq] = OSS_IRQLEV_NUBUS;
                        return;
        }

        if (IRQ_SRC(irq) == 1)
                via_irq_enable(irq);
}

/*
 * Disable an OSS interrupt
 *
 * Same as above except we set the source's interrupt level to zero,
 * to disable the interrupt.
 */

void oss_irq_disable(int irq) {
#ifdef DEBUG_IRQUSE
        printk("oss_irq_disable(%d)\n", irq);
#endif
        switch(irq) {
                case IRQ_MAC_SCC:
                        oss->irq_level[OSS_IOPSCC] = 0;
                        return;
                case IRQ_MAC_ADB:
                        oss->irq_level[OSS_IOPISM] = 0;
                        return;
                case IRQ_MAC_SCSI:
                        oss->irq_level[OSS_SCSI] = 0;
                        return;
                case IRQ_NUBUS_9:
                case IRQ_NUBUS_A:
                case IRQ_NUBUS_B:
                case IRQ_NUBUS_C:
                case IRQ_NUBUS_D:
                case IRQ_NUBUS_E:
                        irq -= NUBUS_SOURCE_BASE;
                        oss->irq_level[irq] = 0;
                        return;
        }

        if (IRQ_SRC(irq) == 1)
                via_irq_disable(irq);
}