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diff --git a/src/VBox/Devices/PC/BIOS/timepci.c b/src/VBox/Devices/PC/BIOS/timepci.c
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+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ * --------------------------------------------------------------------
+ *
+ * This code is based on:
+ *
+ * ROM BIOS for use with Bochs/Plex86/QEMU emulation environment
+ *
+ * Copyright (C) 2002 MandrakeSoft S.A.
+ *
+ * MandrakeSoft S.A.
+ * 43, rue d'Aboukir
+ * 75002 Paris - France
+ * http://www.linux-mandrake.com/
+ * http://www.mandrakesoft.com/
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ *
+ */
+
+/*
+ * Oracle LGPL Disclaimer: For the avoidance of doubt, except that if any license choice
+ * other than GPL or LGPL is available it will apply instead, Oracle elects to use only
+ * the Lesser General Public License version 2.1 (LGPLv2) at this time for any software where
+ * a choice of LGPL license versions is made available with the language indicating
+ * that LGPLv2 or any later version may be used, or where a choice of which version
+ * of the LGPL is applied is otherwise unspecified.
+ */
+
+
+#include <stdint.h>
+#include "biosint.h"
+#include "inlines.h"
+
+#if DEBUG_INT1A
+# define BX_DEBUG_INT1A(...) BX_DEBUG(__VA_ARGS__)
+#else
+# define BX_DEBUG_INT1A(...)
+#endif
+
+// for access to RAM area which is used by interrupt vectors
+// and BIOS Data Area
+
+typedef struct {
+ uint8_t filler1[0x400];
+ uint8_t filler2[0x6c];
+ uint16_t ticks_low;
+ uint16_t ticks_high;
+ uint8_t midnight_flag;
+} bios_data_t;
+
+#define BiosData ((bios_data_t __far *) 0)
+
+void init_rtc(void)
+{
+ outb_cmos(0x0a, 0x26);
+ outb_cmos(0x0b, 0x02);
+ inb_cmos(0x0c);
+ inb_cmos(0x0d);
+}
+
+bx_bool rtc_updating(void)
+{
+ // This function checks to see if the update-in-progress bit
+ // is set in CMOS Status Register A. If not, it returns 0.
+ // If it is set, it tries to wait until there is a transition
+ // to 0, and will return 0 if such a transition occurs. A 1
+ // is returned only after timing out. The maximum period
+ // that this bit should be set is constrained to 244useconds.
+ // The count I use below guarantees coverage or more than
+ // this time, with any reasonable IPS setting.
+
+ uint16_t iter;
+
+ iter = 25000;
+ while (--iter != 0) {
+ if ( (inb_cmos(0x0a) & 0x80) == 0 )
+ return 0;
+ }
+ return 1; // update-in-progress never transitioned to 0
+}
+
+
+extern void eoi_both_pics(void); /* in assembly code */
+#pragma aux eoi_both_pics "*";
+
+void call_int_4a(void);
+#pragma aux call_int_4a = "int 4Ah";
+
+void BIOSCALL int70_function(pusha_regs_t regs, uint16_t ds, uint16_t es, iret_addr_t iret_addr)
+{
+ // INT 70h: IRQ 8 - CMOS RTC interrupt from periodic or alarm modes
+ uint8_t registerB = 0, registerC = 0;
+
+ // Check which modes are enabled and have occurred.
+ registerB = inb_cmos( 0xB );
+ registerC = inb_cmos( 0xC );
+
+ if( ( registerB & 0x60 ) != 0 ) {
+ if( ( registerC & 0x20 ) != 0 ) {
+ // Handle Alarm Interrupt.
+ int_enable();
+ call_int_4a();
+ int_disable();
+ }
+ if( ( registerC & 0x40 ) != 0 ) {
+ // Handle Periodic Interrupt.
+
+ if( read_byte( 0x40, 0xA0 ) != 0 ) {
+ // Wait Interval (Int 15, AH=83 or AH=86) active.
+ uint32_t time;
+
+ time = read_dword( 0x40, 0x9C ); // Time left in microseconds.
+ if( time < 0x3D1 ) {
+ // Done waiting.
+ uint16_t segment, offset;
+
+ segment = read_word( 0x40, 0x98 );
+ offset = read_word( 0x40, 0x9A );
+ write_byte( 0x40, 0xA0, 0 ); // Turn off status byte.
+ outb_cmos( 0xB, registerB & 0x37 ); // Clear the Periodic Interrupt.
+ write_byte( segment, offset, read_byte(segment, offset) | 0x80 ); // Write to specified flag byte.
+ } else {
+ // Continue waiting.
+ time -= 0x3D1;
+ write_dword( 0x40, 0x9C, time );
+ }
+ }
+ }
+ }
+ eoi_both_pics();
+}
+
+/// @todo the coding style WRT register access is totally inconsistent
+// in the following routines
+
+void BIOSCALL int1a_function(pusha_regs_t regs, uint16_t ds, uint16_t es, iret_addr_t iret_addr)
+{
+ uint8_t val8;
+
+ BX_DEBUG_INT1A("int1a: AX=%04x BX=%04x CX=%04x DX=%04x DS=%04x\n",
+ regs.u.r16.ax, regs.u.r16.bx, regs.u.r16.cx, regs.u.r16.dx, ds);
+ int_enable();
+
+ switch (regs.u.r8.ah) {
+ case 0: // get current clock count
+ int_disable();
+ regs.u.r16.cx = BiosData->ticks_high;
+ regs.u.r16.dx = BiosData->ticks_low;
+ regs.u.r8.al = BiosData->midnight_flag;
+ BiosData->midnight_flag = 0; // reset flag
+ int_enable();
+ // AH already 0
+ ClearCF(iret_addr.flags); // OK
+ break;
+
+ case 1: // Set Current Clock Count
+ int_disable();
+ BiosData->ticks_high = regs.u.r16.cx;
+ BiosData->ticks_low = regs.u.r16.dx;
+ BiosData->midnight_flag = 0; // reset flag
+ int_enable();
+ regs.u.r8.ah = 0;
+ ClearCF(iret_addr.flags); // OK
+ break;
+
+ case 2: // Read CMOS Time
+ if (rtc_updating()) {
+ SetCF(iret_addr.flags);
+ break;
+ }
+
+ regs.u.r8.dh = inb_cmos(0x00); // Seconds
+ regs.u.r8.cl = inb_cmos(0x02); // Minutes
+ regs.u.r8.ch = inb_cmos(0x04); // Hours
+ regs.u.r8.dl = inb_cmos(0x0b) & 0x01; // Stat Reg B
+ regs.u.r8.ah = 0;
+ regs.u.r8.al = regs.u.r8.ch;
+ ClearCF(iret_addr.flags); // OK
+ break;
+
+ case 3: // Set CMOS Time
+ // Using a debugger, I notice the following masking/setting
+ // of bits in Status Register B, by setting Reg B to
+ // a few values and getting its value after INT 1A was called.
+ //
+ // try#1 try#2 try#3
+ // before 1111 1101 0111 1101 0000 0000
+ // after 0110 0010 0110 0010 0000 0010
+ //
+ // Bit4 in try#1 flipped in hardware (forced low) due to bit7=1
+ // My assumption: RegB = ((RegB & 01100000b) | 00000010b)
+ if (rtc_updating()) {
+ init_rtc();
+ // fall through as if an update were not in progress
+ }
+ outb_cmos(0x00, regs.u.r8.dh); // Seconds
+ outb_cmos(0x02, regs.u.r8.cl); // Minutes
+ outb_cmos(0x04, regs.u.r8.ch); // Hours
+ // Set Daylight Savings time enabled bit to requested value
+ val8 = (inb_cmos(0x0b) & 0x60) | 0x02 | (regs.u.r8.dl & 0x01);
+ // (reg B already selected)
+ outb_cmos(0x0b, val8);
+ regs.u.r8.ah = 0;
+ regs.u.r8.al = val8; // val last written to Reg B
+ ClearCF(iret_addr.flags); // OK
+ break;
+
+ case 4: // Read CMOS Date
+ regs.u.r8.ah = 0;
+ if (rtc_updating()) {
+ SetCF(iret_addr.flags);
+ break;
+ }
+ regs.u.r8.cl = inb_cmos(0x09); // Year
+ regs.u.r8.dh = inb_cmos(0x08); // Month
+ regs.u.r8.dl = inb_cmos(0x07); // Day of Month
+ regs.u.r8.ch = inb_cmos(0x32); // Century
+ regs.u.r8.al = regs.u.r8.ch;
+ ClearCF(iret_addr.flags); // OK
+ break;
+
+ case 5: // Set CMOS Date
+ // Using a debugger, I notice the following masking/setting
+ // of bits in Status Register B, by setting Reg B to
+ // a few values and getting its value after INT 1A was called.
+ //
+ // try#1 try#2 try#3 try#4
+ // before 1111 1101 0111 1101 0000 0010 0000 0000
+ // after 0110 1101 0111 1101 0000 0010 0000 0000
+ //
+ // Bit4 in try#1 flipped in hardware (forced low) due to bit7=1
+ // My assumption: RegB = (RegB & 01111111b)
+ if (rtc_updating()) {
+ init_rtc();
+ SetCF(iret_addr.flags);
+ break;
+ }
+ outb_cmos(0x09, regs.u.r8.cl); // Year
+ outb_cmos(0x08, regs.u.r8.dh); // Month
+ outb_cmos(0x07, regs.u.r8.dl); // Day of Month
+ outb_cmos(0x32, regs.u.r8.ch); // Century
+ val8 = inb_cmos(0x0b) & 0x7f; // clear halt-clock bit
+ outb_cmos(0x0b, val8);
+ regs.u.r8.ah = 0;
+ regs.u.r8.al = val8; // AL = val last written to Reg B
+ ClearCF(iret_addr.flags); // OK
+ break;
+
+ case 6: // Set Alarm Time in CMOS
+ // Using a debugger, I notice the following masking/setting
+ // of bits in Status Register B, by setting Reg B to
+ // a few values and getting its value after INT 1A was called.
+ //
+ // try#1 try#2 try#3
+ // before 1101 1111 0101 1111 0000 0000
+ // after 0110 1111 0111 1111 0010 0000
+ //
+ // Bit4 in try#1 flipped in hardware (forced low) due to bit7=1
+ // My assumption: RegB = ((RegB & 01111111b) | 00100000b)
+ val8 = inb_cmos(0x0b); // Get Status Reg B
+ regs.u.r16.ax = 0;
+ if (val8 & 0x20) {
+ // Alarm interrupt enabled already
+ SetCF(iret_addr.flags); // Error: alarm in use
+ break;
+ }
+ if (rtc_updating()) {
+ init_rtc();
+ // fall through as if an update were not in progress
+ }
+ outb_cmos(0x01, regs.u.r8.dh); // Seconds alarm
+ outb_cmos(0x03, regs.u.r8.cl); // Minutes alarm
+ outb_cmos(0x05, regs.u.r8.ch); // Hours alarm
+ outb(0xa1, inb(0xa1) & 0xfe); // enable IRQ 8
+ // enable Status Reg B alarm bit, clear halt clock bit
+ outb_cmos(0x0b, (val8 & 0x7f) | 0x20);
+ ClearCF(iret_addr.flags); // OK
+ break;
+
+ case 7: // Turn off Alarm
+ // Using a debugger, I notice the following masking/setting
+ // of bits in Status Register B, by setting Reg B to
+ // a few values and getting its value after INT 1A was called.
+ //
+ // try#1 try#2 try#3 try#4
+ // before 1111 1101 0111 1101 0010 0000 0010 0010
+ // after 0100 0101 0101 0101 0000 0000 0000 0010
+ //
+ // Bit4 in try#1 flipped in hardware (forced low) due to bit7=1
+ // My assumption: RegB = (RegB & 01010111b)
+ val8 = inb_cmos(0x0b); // Get Status Reg B
+ // clear clock-halt bit, disable alarm bit
+ outb_cmos(0x0b, val8 & 0x57); // disable alarm bit
+ regs.u.r8.ah = 0;
+ regs.u.r8.al = val8; // val last written to Reg B
+ ClearCF(iret_addr.flags); // OK
+ break;
+
+ default:
+ BX_DEBUG_INT1A("int1a: AX=%04x unsupported\n", regs.u.r16.ax);
+ SetCF(iret_addr.flags); // Unsupported
+ }
+}
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