From 6412d01deb4b375ff5965e6f13dacb5928059919 Mon Sep 17 00:00:00 2001
From: SarahW <pcem@pcem-emulator.co.uk>
Date: Sat, 24 Mar 2018 15:29:10 +0000
Subject: [PATCH] Added level-sensitive IRQs on PIIX and SiS497. Fixes hanging
 audio with AudioPCI on Windows 2000.

---
 src/ibm.h    |  1 +
 src/pic.c    | 49 +++++++++++++++++++++++++++++++++++++++++++++----
 src/pic.h    |  1 +
 src/piix.c   |  3 +++
 src/sis496.c |  3 +++
 5 files changed, 53 insertions(+), 4 deletions(-)

diff --git a/src/ibm.h b/src/ibm.h
index 491116f..5fdb9f6 100644
--- a/src/ibm.h
+++ b/src/ibm.h
@@ -363,6 +363,7 @@ typedef struct PIC
         int icw;
         uint8_t vector;
         int read;
+        uint8_t level_sensitive;
 } PIC;
 
 PIC pic,pic2;
diff --git a/src/pic.c b/src/pic.c
index 26918f3..b1110a4 100644
--- a/src/pic.c
+++ b/src/pic.c
@@ -36,6 +36,8 @@ void pic_reset()
         pic.mask2=0;
         pic2.pend=pic2.ins=0;
         pic_intpending = 0;
+        pic.level_sensitive = 0;
+        pic2.level_sensitive = 0;
 }
 
 void pic_update_mask(uint8_t *mask, uint8_t ins)
@@ -275,6 +277,41 @@ void pic2_init()
         io_sethandler(0x00a0, 0x0002, pic2_read, NULL, NULL, pic2_write, NULL, NULL, NULL);
 }
 
+static uint8_t pic_elcrx_read(uint16_t addr, void *p)
+{
+        uint8_t temp = 0xff;
+
+        switch (addr)
+        {
+                case 0x4d0:
+                temp = pic.level_sensitive;
+                break;
+                case 0x4d1:
+                temp = pic2.level_sensitive;
+                break;
+        }
+        
+        return temp;
+}
+
+static void pic_elcrx_write(uint16_t addr, uint8_t val, void *p)
+{
+//        pclog("pic_elcrx_write: addr=%04x val=%02x\n", addr, val);
+        switch (addr)
+        {
+                case 0x4d0:
+                pic.level_sensitive = val & 0xf8;
+                break;
+                case 0x4d1:
+                pic2.level_sensitive = val & 0xde;
+                break;
+        }
+}
+
+void pic_init_elcrx()
+{
+        io_sethandler(0x04d0, 0x0002, pic_elcrx_read, NULL, NULL, pic_elcrx_write, NULL, NULL, NULL);
+}
 
 void clearpic()
 {
@@ -364,7 +401,8 @@ uint8_t picinterrupt()
         {
                 if (temp & (1 << c))
                 {
-                        pic.pend &= ~(1 << c);
+                        if (!(pic.level_sensitive & (1 << c)))
+                                pic.pend &= ~(1 << c);
                         pic.ins |= (1 << c);
                         pic_update_mask(&pic.mask2, pic.ins);                      
                    
@@ -385,11 +423,13 @@ uint8_t picinterrupt()
                 {
                         if (temp2 & (1 << c))
                         {
-                                pic2.pend &= ~(1 << c);
+                                if (!(pic2.level_sensitive & (1 << c)))
+                                        pic2.pend &= ~(1 << c);
                                 pic2.ins |= (1 << c);
                                 pic_update_mask(&pic2.mask2, pic2.ins);
                         
-                                pic.pend &= ~(1 << c);
+                                if (!(pic2.level_sensitive & (1 << c)))
+                                        pic.pend &= ~(1 << c);
                                 pic.ins |= (1 << 2); /*Cascade IRQ*/
                                 pic_update_mask(&pic.mask2, pic.ins);
 
@@ -406,7 +446,8 @@ uint8_t picinterrupt()
         {
                 if (temp & (1 << c))
                 {
-                        pic.pend &= ~(1 << c);
+                        if (!(pic.level_sensitive & (1 << c)))
+                                pic.pend &= ~(1 << c);
                         pic.ins |= (1 << c);
                         pic_update_mask(&pic.mask2, pic.ins);                      
                         pic_updatepending();
diff --git a/src/pic.h b/src/pic.h
index e386313..1e129f3 100644
--- a/src/pic.h
+++ b/src/pic.h
@@ -1,5 +1,6 @@
 void pic_init();
 void pic2_init();
+void pic_init_elcrx();
 void pic_reset();
 
 void picint(uint16_t num);
diff --git a/src/piix.c b/src/piix.c
index b902419..342cce5 100644
--- a/src/piix.c
+++ b/src/piix.c
@@ -10,6 +10,7 @@
 #include "io.h"
 #include "mem.h"
 #include "pci.h"
+#include "pic.h"
 
 #include "piix.h"
 
@@ -386,4 +387,6 @@ void piix_init(int card, int pci_a, int pci_b, int pci_c, int pci_d)
         
         ide_pri_disable();
         ide_sec_disable();
+        
+        pic_init_elcrx();
 }
diff --git a/src/sis496.c b/src/sis496.c
index a5ec77f..b958feb 100644
--- a/src/sis496.c
+++ b/src/sis496.c
@@ -4,6 +4,7 @@
 #include "io.h"
 #include "mem.h"
 #include "pci.h"
+#include "pic.h"
 
 #include "sis496.h"
 
@@ -137,6 +138,8 @@ void *sis496_init()
         pci_set_card_routing(13, PCI_INTD);
         pci_set_card_routing(11, PCI_INTC);
 
+        pic_init_elcrx();
+        
 	return sis496;
 }