patch-2.2.18 linux/arch/m68k/mac/via.c

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diff -u --new-file --recursive --exclude-from /usr/src/exclude v2.2.17/arch/m68k/mac/via.c linux/arch/m68k/mac/via.c
@@ -0,0 +1,788 @@
+/*
+ *	6522 Versatile Interface Adapter (VIA)
+ *
+ *	There are two of these on the Mac II. Some IRQ's 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
+ *
+ * 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 <asm/bootinfo.h> 
+#include <asm/macintosh.h> 
+#include <asm/macints.h>
+#include <asm/machw.h> 
+#include <asm/mac_via.h>
+#include <asm/mac_psc.h>
+
+volatile __u8 *via1, *via2;
+#if 0
+/* See note in mac_via.h about how this is possibly not useful */
+volatile long *via_memory_bogon=(long *)&via_memory_bogon;
+#endif
+int  rbv_present,via_alt_mapping;
+__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
+ * _consistantly_ 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)
+
+static int  nubus_active;
+
+void via_debug_dump(void);
+void via1_irq(int, void *, struct pt_regs *);
+void via2_irq(int, void *, struct pt_regs *);
+void via_nubus_irq(int, void *, struct pt_regs *);
+void via_irq_enable(int irq);
+void via_irq_disable(int irq);
+void via_irq_clear(int irq);
+
+extern void mac_bang(int, void *, struct pt_regs *);
+extern void mac_SCC_handler(int, void *, struct pt_regs *);
+extern int console_loglevel;
+extern int oss_present;
+
+/*
+ * 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.
+ */
+
+__initfunc(void 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("VIA1 at %p is a 6522 or clone\n", via1);
+
+	printk("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.
+	 */
+
+	via_write(via1, vIER, 0x7F);	 
+	via_write(via1, vIFR, 0x7F);	 
+	via_write(via1, vT1LL, 0);
+	via_write(via1, vT1LH, 0);
+	via_write(via1, vT1CL, 0);
+	via_write(via1, vT1CH, 0);
+	via_write(via1, vT2CL, 0);
+	via_write(via1, vT2CH, 0);
+	via_write(via1, vACR, via_read(via1, vACR) & 0x3F);
+
+	/* 
+	 * SE/30: disable video IRQ
+	 * XXX: testing for SE/30 VBL
+	 */
+
+	if (macintosh_config->ident == MAC_MODEL_SE30) {
+		via_write(via1, vBufB, via_read(via1, vBufB) | 0x40);
+		via_write(via1, vDirB, via_read(via1, vDirB) | 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).
+	 */
+
+	via_write(via1, vDirB, via_read(via1, vDirB) | (VIA1B_vRTCEnb |
+						        VIA1B_vRTCClk |
+						        VIA1B_vRTCData));
+	via_write(via1, vBufB, via_read(via1, vBufB) | (VIA1B_vRTCEnb |
+						        VIA1B_vRTCClk));
+
+	/* Everything below this point is VIA2/RBV only... */
+
+	if (oss_present) return;
+
+#if 1
+	/* Some machines support an alternate IRQ mapping that spreads  */
+	/* Ethernet and Sound out to their own autolevel IRQs and moves */
+	/* VIA1 to level 6. A/UX uses this mapping and we do too.  Note */
+	/* that the IIfx emulates this alternate mapping using the OSS. */
+
+	switch(macintosh_config->ident) {
+		case MAC_MODEL_C610:
+		case MAC_MODEL_Q610:
+		case MAC_MODEL_C650:
+		case MAC_MODEL_Q650:
+		case MAC_MODEL_Q700:
+		case MAC_MODEL_Q800:
+		case MAC_MODEL_Q900:
+		case MAC_MODEL_Q950:
+			via_alt_mapping = 1;
+			via_write(via1, vDirB, via_read(via1, vDirB) | 0x40);
+			via_write(via1, vBufB, via_read(via1, vBufB) & ~0x40);
+			break;
+		default:
+			via_alt_mapping = 0;
+			break;
+	}
+#else
+	via_alt_mapping = 0;
+#endif
+
+	/*
+	 * Now initialize VIA2. For RBV we just kill all interrupts;
+	 * for a regular VIA we also reset the timers and stuff.
+	 */
+
+	via_write(via2, gIER, 0x7F);	 
+	via_write(via2, gIFR, 0x7F | rbv_clear);	 
+	if (!rbv_present) {
+		via_write(via2, vT1LL, 0);
+		via_write(via2, vT1LH, 0);
+		via_write(via2, vT1CL, 0);
+		via_write(via2, vT1CH, 0);
+		via_write(via2, vT2CL, 0);
+		via_write(via2, vT2CH, 0);
+		via_write(via2, vACR, via_read(via2, vACR) & 0x3F);
+	}
+}
+
+/*
+ * Start the 100 Hz clock
+ */
+
+__initfunc(void via_init_clock(void (*func)(int, void *, struct pt_regs *)))
+{	
+	via_write(via1, vACR, via_read(via1, vACR) | 0x40);
+	via_write(via1, vT1LL, MAC_CLOCK_LOW);
+	via_write(via1, vT1LH, MAC_CLOCK_HIGH);
+	via_write(via1, vT1CL, MAC_CLOCK_LOW);
+	via_write(via1, vT1CH, MAC_CLOCK_HIGH);
+	
+	request_irq(IRQ_MAC_TIMER_1, func, IRQ_FLG_LOCK, "timer", func);
+}
+
+/*
+ * Register the interrupt dispatchers for VIA or RBV machines only.
+ */
+
+__initfunc(void via_register_interrupts(void))
+{
+	if (via_alt_mapping) {
+		sys_request_irq(IRQ_AUTO_1, via1_irq, IRQ_FLG_LOCK|IRQ_FLG_FAST,
+				"Software IRQ", (void *) via1);
+		sys_request_irq(IRQ_AUTO_6, via1_irq, IRQ_FLG_LOCK|IRQ_FLG_FAST,
+				"VIA1 Dispatch", (void *) via1);
+	} else {
+		sys_request_irq(IRQ_AUTO_1, via1_irq, IRQ_FLG_LOCK|IRQ_FLG_FAST,
+				"VIA1 Dispatch", (void *) via1);
+#if 0 /* interferes with serial on some machines */
+		if (!psc_present) {
+			sys_request_irq(IRQ_AUTO_6, mac_bang, IRQ_FLG_LOCK,
+					"Off Switch", mac_bang);
+		}
+#endif
+	}
+	sys_request_irq(IRQ_AUTO_2, via2_irq, IRQ_FLG_LOCK|IRQ_FLG_FAST,
+			"VIA2 Dispatch", (void *) via2);
+	if (!psc_present) {
+		sys_request_irq(IRQ_AUTO_4, mac_SCC_handler, IRQ_FLG_LOCK,
+				"SCC Dispatch", mac_SCC_handler);
+	}
+	request_irq(IRQ_MAC_NUBUS, via_nubus_irq, IRQ_FLG_LOCK|IRQ_FLG_FAST,
+			"Nubus Dispatch", (void *) via2);
+}
+
+/*
+ * Debugging dump, used in various places to see what's going on.
+ */
+
+void via_debug_dump(void)
+{
+	printk("VIA1: DDRA = 0x%02X DDRB = 0x%02X ACR = 0x%02X\n",
+		via_read(via1, vDirA),
+		via_read(via1, vDirB),
+		via_read(via1, vACR));
+	printk("         PCR = 0x%02X  IFR = 0x%02X IER = 0x%02X\n",
+		via_read(via1, vPCR),
+		via_read(via1, vIFR),
+		via_read(via1, vIER));
+	if (oss_present) {
+		printk("VIA2: <OSS>\n");
+	} else if (rbv_present) {
+		printk("VIA2:  IFR = 0x%02X  IER = 0x%02X\n",
+			via_read(via2, rIFR),
+			via_read(via2, rIER));
+		printk("      SIFR = 0x%02X SIER = 0x%02X\n",
+			via_read(via2, rSIFR),
+			via_read(via2, rSIER));
+	} else {
+		printk("VIA2: DDRA = 0x%02X DDRB = 0x%02X ACR = 0x%02X\n",
+			via_read(via2, vDirA),
+			via_read(via2, vDirB),
+			via_read(via2, vACR));
+		printk("         PCR = 0x%02X  IFR = 0x%02X IER = 0x%02X\n",
+			via_read(via2, vPCR),
+			via_read(via2, vIFR),
+			via_read(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 = via_read(via1, vT1CL) + (via_read(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 (via_read(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)
+{
+	via_write(via2, gBufB, via_read(via2, vBufB) & ~VIA2B_vMode32);
+	via_write(via2, gBufB, via_read(via2, vBufB) | 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 via_read(via2, gBufB) & VIA2B_vCDis;
+}
+
+/*
+ * VIA-based power switch, for machines that support it.
+ */
+
+void via_poweroff(void)
+{
+	if (rbv_present) {
+		via_write(via2, rBufB, via_read(via2, rBufB) & ~0x04);
+	} else {
+		/* Direction of vDirB is output */
+		via_write(via2, vDirB, via_read(via2, vDirB) | 0x04);
+		/* Send a value of 0 on that line */
+		via_write(via2, vBufB, via_read(via2, vBufB) & ~0x04);
+		/* Otherwise it prints "It is now.." then shuts off */
+		mdelay(1000);
+	}
+
+	/* We should never make it this far... */
+	printk ("It is now safe to switch off your machine.\n");
+	while(1);
+}
+
+/*
+ * Initialize VIA2 for Nubus access
+ */
+
+__initfunc(void via_nubus_init(void))
+{
+	nubus_active = 0;
+
+	/* unlock nubus transactions */
+
+	if (!rbv_present) {
+		/* set the line to be an output on non-RBV machines */
+		via_write(via2, vDirB, via_read(via2, vDirB) | 0x02);
+	}
+	via_write(via2, gBufB, via_read(via2, gBufB) | 0x02);
+
+	/* disable nubus slot interrupts. */
+	if (rbv_present) {
+		via_write(via2, rSIER, 0x7F); /* like VIA; bit 7=clr,set */
+		if ((via_read(via2, rSIER) & 0x7F) != 0) {
+			printk("SIER not behaving properly: "
+				"email <cananian@alumni.princeton.edu>\n");
+		}
+	} else {
+		via_write(via2, vBufA, 0xFF); /* active low irqs, force high */
+		via_write(via2, vDirA, 0xFF); /* ddr to output. */
+	}
+}
+
+/*
+ * The generic VIA interrupt routines (shamelessly stolen from Alan Cox's
+ * via6522.c :-), disable/pending masks added.
+ *
+ * The new interrupt architecture in macints.c takes care of a lot of the
+ * gruntwork for us, including tallying the interrupts and calling the
+ * handlers on the linked list. All we need to do here is basically generate
+ * the machspec interrupt number after clearing the interrupt.
+ */
+
+void via1_irq(int irq, void *dev_id, struct pt_regs *regs)
+{
+	int irq_bit, i;
+	unsigned char events, mask;
+
+	mask = via_read(via1, vIER) & 0x7f;
+	events = via_read(via1, vIFR) & mask;
+	if (events == 0) return;
+
+	for (i = 0, irq_bit = 1 ; i < 7 ; i++, irq_bit <<= 1)
+		if (events & irq_bit) {
+			via_write(via1, vIER, irq_bit);
+			via_write(via1, vIFR, irq_bit);
+			mac_do_irq_list(VIA1_SOURCE_BASE + i, regs);
+			via_write(via1, vIER, irq_bit | 0x80);
+		}
+
+	if (!oss_present) {
+		/* This (still) seems to be necessary to get IDE
+		   working.  However, if you enable VBL interrupts,
+		   you're screwed... */
+		/* FIXME: should we check the SLOTIRQ bit before
+                   pulling this stunt? */
+		via_irq_disable(IRQ_MAC_NUBUS);
+		via_irq_clear(IRQ_MAC_NUBUS);
+		mac_do_irq_list(IRQ_MAC_NUBUS, regs);
+		via_irq_enable(IRQ_MAC_NUBUS);
+	}
+}
+
+void via2_irq(int irq, void *dev_id, struct pt_regs *regs)
+{
+	int irq_bit, i;
+	unsigned char events, mask;
+
+	mask = via_read(via2, gIER) & 0x7f;
+	events = via_read(via2, gIFR) & mask;
+	if (events == 0) return;
+
+	for (i = 0, irq_bit = 1 ; i < 7 ; i++, irq_bit <<= 1)
+		if (events & irq_bit) {
+			via_write(via2, gIER, irq_bit);
+			via_write(via2, gIFR, irq_bit | rbv_clear);
+			mac_do_irq_list(VIA2_SOURCE_BASE + i, regs);
+			via_write(via2, gIER, irq_bit | 0x80);
+		}
+}
+
+/*
+ * Dispatch Nubus interrupts. We are called as a secondary dispatch by the
+ * VIA2 dispatcher as a fast interrupt handler.
+ */
+
+void via_nubus_irq(int irq, void *dev_id, struct pt_regs *regs)
+{
+	int irq_bit, i;
+	unsigned char events;
+
+	events = ~via_read(via2, gBufA) & nubus_active;
+	if (events == 0) return;
+
+	for (i = 0, irq_bit = 1 ; i < 7 ; i++, irq_bit <<= 1) {
+		if (events & irq_bit) {
+			via_irq_disable(NUBUS_SOURCE_BASE + i);
+			/* FIXME: this does nothing.  Should we clear
+                           the SLOTIRQ bit here? */
+			via_irq_clear(NUBUS_SOURCE_BASE + i);
+			mac_do_irq_list(NUBUS_SOURCE_BASE + i, regs);
+			via_irq_enable(NUBUS_SOURCE_BASE + i);
+		}
+	}
+}
+
+void via_irq_enable(int irq) {
+	int irq_src	= IRQ_SRC(irq);
+	int irq_idx	= IRQ_IDX(irq);
+	int irq_bit	= 1 << irq_idx;
+
+#ifdef DEBUG_IRQUSE
+	printk("via_irq_enable(%d)\n", irq);
+#endif
+
+	if (irq_src == 1) {
+		via_write(via1, vIER, irq_bit | 0x80);
+	} else if (irq_src == 2) {
+		/*
+		 * Set vPCR for SCSI interrupts (but not on RBV)
+		 */
+		if ((irq_idx == 0) && !rbv_present) {
+			if (macintosh_config->scsi_type == MAC_SCSI_OLD) {
+				/* CB2 (IRQ) indep. input, positive edge */
+				/* CA2 (DRQ) indep. input, positive edge */
+				via_write(via2, vPCR, 0x66);
+			} else {
+				/* CB2 (IRQ) indep. input, negative edge */
+				/* CA2 (DRQ) indep. input, negative edge */
+				via_write(via2, vPCR, 0x22);
+			}
+		}
+		via_write(via2, gIER, irq_bit | 0x80);
+	} else if (irq_src == 7) {
+		if (rbv_present) {
+			/* enable the slot interrupt. SIER works like IER. */
+			via_write(via2, rSIER, IER_SET_BIT(irq_idx));
+		} else {
+			/* Make sure the bit is an input, to enable the irq */
+			via_write(via2, vDirA,
+					via_read(via2, vDirA) & ~irq_bit);
+		}
+		nubus_active |= irq_bit;
+	}
+}
+
+void via_irq_disable(int irq) {
+	int irq_src	= IRQ_SRC(irq);
+	int irq_idx	= IRQ_IDX(irq);
+	int irq_bit	= 1 << irq_idx;
+
+#ifdef DEBUG_IRQUSE
+	printk("via_irq_disable(%d)\n", irq);
+#endif
+
+	if (irq_src == 1) {
+		via_write(via1, vIER, irq_bit);
+	} else if (irq_src == 2) {
+		via_write(via2, gIER, irq_bit);
+	} else if (irq_src == 7) {
+		if (rbv_present) {
+			/* disable the slot interrupt.  SIER works like IER. */
+			via_write(via2, rSIER, IER_CLR_BIT(irq_idx));
+		} else {
+			/* disable the nubus irq by changing dir to output */
+			via_write(via2, vBufA, ~nubus_active);
+			via_write(via2, vDirA, via_read(via2, vDirA) | irq_bit);
+		}
+		nubus_active &= ~irq_bit;
+	}
+}
+
+void via_irq_clear(int irq) {
+	int irq_src	= IRQ_SRC(irq);
+	int irq_idx	= IRQ_IDX(irq);
+	int irq_bit	= 1 << irq_idx;
+
+	if (irq_src == 1) {
+		via_write(via1, vIFR, irq_bit);
+	} else if (irq_src == 2) {
+		via_write(via2, gIFR, irq_bit | rbv_clear);
+	} else if (irq_src == 7) {
+		/* FIXME: hmm.. */
+	}
+}
+
+/*
+ * Returns nonzero if an interrupt is pending on the given
+ * VIA/IRQ combination.
+ */
+
+int via_irq_pending(int irq)
+{
+	int irq_src	= IRQ_SRC(irq);
+	int irq_idx	= IRQ_IDX(irq);
+	int irq_bit	= 1 << irq_idx;
+
+	if (irq_src == 1) {
+		return via_read(via1, vIFR) & irq_bit;
+	} else if (irq_src == 2) {
+		return via_read(via2, gIFR) & irq_bit;
+	} else if (irq_src == 7) {
+		return (~via_read(via2, gBufA)) & irq_bit;
+	}
+	return 0;
+}
+
+void via_scsi_clear(void)
+{
+	volatile unsigned char deep_magic;
+
+#ifdef DEBUG_IRQUSE
+	printk("via_scsi_clear()\n");
+#endif
+
+	/* We handle this in oss.c , but this gets called in mac_scsinew.c */
+	if(oss_present) return;
+
+	if (rbv_present) {
+		via_write(via2, rIFR, (1<<3) | (1<<0) | rbv_clear);
+		deep_magic = via_read(via2, rBufB);
+	} else {
+		deep_magic = via_read(via2, vBufB);
+	}
+	mac_enable_irq((IRQ_IDX(IRQ_MAC_SCSI)));
+}
+
+/*
+ * PRAM/RTC access routines
+ *
+ * Must be called with interrupts disabled and
+ * the RTC should be enabled.
+ */
+
+static __u8 via_pram_readbyte(void)
+{
+	int	i,reg;
+	__u8	data;
+
+	reg = via_read(via1, vBufB) & ~VIA1B_vRTCClk;
+
+	/* Set the RTC data line to be an input. */
+
+	via_write(via1, vDirB, via_read(via1, vDirB) & ~VIA1B_vRTCData);
+
+	/* The bits of the byte come out in MSB order */
+
+	data = 0;
+	for (i = 0 ; i < 8 ; i++) {
+		via_write(via1, vBufB, reg);
+		via_write(via1, vBufB, reg | VIA1B_vRTCClk);
+		data = (data << 1) | (via_read(via1, vBufB) & VIA1B_vRTCData);
+	}
+
+	/* Return RTC data line to output state */
+
+	via_write(via1, vDirB, via_read(via1, vDirB) | VIA1B_vRTCData);
+
+	return data;
+}
+
+static void via_pram_writebyte(__u8 data)
+{
+	int	i,reg,bit;
+
+	reg = via_read(via1, vBufB) & ~(VIA1B_vRTCClk | VIA1B_vRTCData);
+
+	/* The bits of the byte go in in MSB order */
+
+	for (i = 0 ; i < 8 ; i++) {
+		bit = data & 0x80? 1 : 0;
+		data <<= 1;
+		via_write(via1, vBufB, reg | bit);
+		via_write(via1, vBufB, reg | bit | VIA1B_vRTCClk);
+	}
+}
+
+/*
+ * Execute a PRAM/RTC command. For read commands
+ * data should point to a one-byte buffer for the
+ * resulting data. For write commands it should point
+ * to the data byte to for the command.
+ *
+ * This function disables all interrupts while running.
+ */
+
+void via_pram_command(int command, __u8 *data)
+{
+	unsigned long cpu_flags;
+	int	is_read,tmp;
+
+	save_flags(cpu_flags);
+	cli();
+
+	/* Enable the RTC and make sure the strobe line is high */
+
+	tmp = (via_read(via1, vBufB) | VIA1B_vRTCClk) & ~VIA1B_vRTCEnb;
+	via_write(via1, vBufB, tmp);
+
+	if (command & 0xFF00) {		/* extended (two-byte) command */
+		via_pram_writebyte((command & 0xFF00) >> 8);
+		via_pram_writebyte(command & 0xFF);
+		is_read = command & 0x8000;
+	} else {			/* one-byte command */
+		via_pram_writebyte(command);
+		is_read = command & 0x80;
+	}
+	if (is_read) {
+		*data = via_pram_readbyte();
+	} else {
+		via_pram_writebyte(*data);
+	}
+
+	/* All done, disable the RTC */
+
+	via_write(via1, vBufB, via_read(via1, vBufB) | VIA1B_vRTCEnb);
+
+	restore_flags(cpu_flags);
+}
+
+/*
+ * Return the current time in seconds since January 1, 1904.
+ *
+ * This only works on machines with the VIA-based PRAM/RTC, which
+ * is basically any machine with Mac II-style ADB.
+ */
+
+__u32 via_read_time(void)
+{
+	union {
+		__u8  cdata[4];
+		__u32 idata;
+	} result, last_result;
+	int	ct;
+
+	/*
+	 * The NetBSD guys say to loop until you get the same reading
+	 * twice in a row.
+	 */
+
+	ct = 0;
+	do {
+		if (++ct > 10) {
+			printk("via_read_time: couldn't get valid time, "
+			       "last read = 0x%08X and 0x%08X\n", last_result.idata,
+			       result.idata);
+			break;
+		}
+
+		last_result.idata = result.idata;
+		result.idata = 0;
+
+		via_pram_command(0x81, &result.cdata[3]);
+		via_pram_command(0x85, &result.cdata[2]);
+		via_pram_command(0x89, &result.cdata[1]);
+		via_pram_command(0x8D, &result.cdata[0]);
+	} while (result.idata != last_result.idata);
+
+	return result.idata;
+}
+
+/*
+ * Set the current time to a number of seconds since January 1, 1904.
+ *
+ * This only works on machines with the VIA-based PRAM/RTC, which
+ * is basically any machine with Mac II-style ADB.
+ */
+
+void via_write_time(__u32 time)
+{
+	union {
+		__u8  cdata[4];
+		__u32 idata;
+	} data;
+	__u8	temp;
+
+	/* Clear the write protect bit */
+
+	temp = 0x55;
+	via_pram_command(0x35, &temp);
+
+	data.idata = time;
+	via_pram_command(0x01, &data.cdata[3]);
+	via_pram_command(0x05, &data.cdata[2]);
+	via_pram_command(0x09, &data.cdata[1]);
+	via_pram_command(0x0D, &data.cdata[0]);
+
+	/* Set the write protect bit */
+
+	temp = 0xD5;
+	via_pram_command(0x35, &temp);
+}
FUNET's LINUX-ADM group, linux-adm@nic.funet.fi
TCL-scripts by Sam Shen (who was at: slshen@lbl.gov)