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+// 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>
+
+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.
+ */
+
+ 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;
+}
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