From 32eb2c8cd20a21a24d8f1e78ebabc1b20d657531 Mon Sep 17 00:00:00 2001
From: Floogle <18466542+skyfloogle@users.noreply.github.com>
Date: Tue, 9 Jan 2024 19:50:49 +0100
Subject: [PATCH] allow late timer interrupts

---
 include/v810_cpu.h       |  2 +-
 source/common/v810_cpu.c | 24 ++++++++++++++----------
 source/common/v810_mem.c |  2 +-
 3 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/include/v810_cpu.h b/include/v810_cpu.h
index 56d883b..84371c4 100644
--- a/include/v810_cpu.h
+++ b/include/v810_cpu.h
@@ -120,7 +120,7 @@ void v810_exit();
 void v810_reset();
 
 // Generate Interupt #n
-void v810_int(WORD iNum, WORD PC);
+bool v810_int(WORD iNum, WORD PC);
 
 // Generate Exception #n
 void v810_exp(WORD iNum, WORD eCode);
diff --git a/source/common/v810_cpu.c b/source/common/v810_cpu.c
index c16fcf3..5ac38c1 100644
--- a/source/common/v810_cpu.c
+++ b/source/common/v810_cpu.c
@@ -206,14 +206,17 @@ int serviceInt(unsigned int cycles, WORD PC) {
             if (tHReg.tCount <= 0) {
                 tHReg.tCount += tHReg.tTHW; //reset counter
                 tHReg.TCR |= 0x02; //Zero Status
-                if (tHReg.TCR & 0x08) {
-                    v810_int(1, PC);
-                    return 1;
-                }
             }
             tHReg.TLB = (tHReg.tCount&0xFF);
             tHReg.THB = ((tHReg.tCount>>8)&0xFF);
         }
+        if ((tHReg.TCR & 0x02) && (tHReg.TCR & 0x08)) {
+            // zero & interrupt enabled
+            return v810_int(1, PC);
+        }
+    } else {
+        // don't get too overzealous if we turn it off and on again
+        lasttime = cycles;
     }
 
     return 0;
@@ -332,12 +335,12 @@ int serviceDisplayInt(unsigned int cycles, WORD PC) {
 }
 
 // Generate Interupt #n
-void v810_int(WORD iNum, WORD PC) {
-    if (iNum > 0x0F) return;  // Invalid Interupt number...
-    if((v810_state->S_REG[PSW] & PSW_NP)) return;
-    if((v810_state->S_REG[PSW] & PSW_EP)) return; // Exception pending?
-    if((v810_state->S_REG[PSW] & PSW_ID)) return; // Interupt disabled
-    if(iNum < ((v810_state->S_REG[PSW] & PSW_IA)>>16)) return; // Interupt to low on the chain
+bool v810_int(WORD iNum, WORD PC) {
+    if (iNum > 0x0F) return false;  // Invalid Interupt number...
+    if((v810_state->S_REG[PSW] & PSW_NP)) return false;
+    if((v810_state->S_REG[PSW] & PSW_EP)) return false; // Exception pending?
+    if((v810_state->S_REG[PSW] & PSW_ID)) return false; // Interupt disabled
+    if(iNum < ((v810_state->S_REG[PSW] & PSW_IA)>>16)) return false; // Interupt to low on the chain
 
     dprintf(1, "[INT]: iNum=0x%lx\n", iNum);
 
@@ -354,6 +357,7 @@ void v810_int(WORD iNum, WORD PC) {
     if((iNum+=1) > 0x0F)
         (iNum = 0x0F);
     v810_state->S_REG[PSW] = v810_state->S_REG[PSW] | (iNum << 16); //Set the Interupt
+    return true;
 }
 
 // Generate exception #n
diff --git a/source/common/v810_mem.c b/source/common/v810_mem.c
index 498d62c..9c8d7f4 100644
--- a/source/common/v810_mem.c
+++ b/source/common/v810_mem.c
@@ -515,7 +515,7 @@ void hcreg_wbyte(WORD addr, BYTE data) {
         }
 
         tHReg.TCR = (((data|0xE4)&0xFD)|(tHReg.TCR&0x02));
-        if ((data & 0x04) && (!(tHReg.TCR & 0x01))) { //cannot clear ZStat if timer is enabled...
+        if ((data & 0x05) == 0x04 || !(data & 0x08)) {
             tHReg.TCR &= 0xFD; // Clear the ZStat Flag...
         }
         break;