arch/m68k/mac/via.c - linux - Git at Google

 // 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/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>

 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 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[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
 	 */

 	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[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 */
 	}

 	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;
 	}
 }

 /*
  * 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 (!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]);
 	}
 }

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

 u32 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) * 1000;
 }

 /*
  * 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
  */

 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);
 		}
 		/* 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(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(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);
	// 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/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>

	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 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[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
	*/

	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[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 */
	}

	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;
	}
	}

	/*
	* 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 (!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]);
	}
	}

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

	u32 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) * 1000;
	}

	/*
	* 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
	*/

	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);
	}
	/* 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(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(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);