From eee24961b1f2b2bcdb50b132486c8690b8d7237c Mon Sep 17 00:00:00 2001
From: Jeffrey Pfau <jeffrey@endrift.com>
Date: Tue, 26 Jan 2016 20:57:34 -0800
Subject: [PATCH] GB: Partially fix timers

---
 src/gb/io.c    |  4 +---
 src/gb/timer.c | 18 +++++++++++-------
 src/gb/timer.h |  1 +
 3 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/src/gb/io.c b/src/gb/io.c
index 3a0bb95ea..c8a38d131 100644
--- a/src/gb/io.c
+++ b/src/gb/io.c
@@ -55,10 +55,8 @@ void GBIOWrite(struct GB* gb, unsigned address, uint8_t value) {
 	case REG_DIV:
 		GBTimerDivReset(&gb->timer);
 		return;
-	case REG_TIMA:
-		// ???
-		return;
 	case REG_JOYP:
+	case REG_TIMA:
 	case REG_TMA:
 	case REG_LYC:
 		// Handled transparently by the registers
diff --git a/src/gb/timer.c b/src/gb/timer.c
index 45a07fa45..47b240563 100644
--- a/src/gb/timer.c
+++ b/src/gb/timer.c
@@ -71,15 +71,19 @@ uint8_t GBTimerUpdateTAC(struct GBTimer* timer, GBRegisterTAC tac) {
 			timer->timaPeriod = 256;
 			break;
 		}
-		timer->nextTima = timer->eventDiff + timer->timaPeriod;
-		if (timer->nextTima < timer->nextEvent) {
-			timer->nextEvent = timer->nextTima;
-			if (timer->nextEvent < timer->p->cpu->nextEvent) {
-				timer->p->cpu->nextEvent = timer->nextEvent;
-			}
-		}
+		GBTimerUpdateTIMA(timer);
 	} else {
 		timer->nextTima = INT_MAX;
 	}
 	return tac;
 }
+
+void GBTimerUpdateTIMA(struct GBTimer* timer) {
+	timer->nextTima = timer->eventDiff + timer->p->cpu->cycles + timer->timaPeriod;
+	if (timer->eventDiff + timer->timaPeriod < timer->nextEvent) {
+		timer->nextEvent = timer->eventDiff + timer->timaPeriod;
+		if (timer->nextEvent < timer->p->cpu->nextEvent) {
+			timer->p->cpu->nextEvent = timer->nextEvent;
+		}
+	}
+}
diff --git a/src/gb/timer.h b/src/gb/timer.h
index af31ea81f..c650dad3a 100644
--- a/src/gb/timer.h
+++ b/src/gb/timer.h
@@ -32,5 +32,6 @@ void GBTimerReset(struct GBTimer*);
 int32_t GBTimerProcessEvents(struct GBTimer*, int32_t cycles);
 void GBTimerDivReset(struct GBTimer*);
 uint8_t GBTimerUpdateTAC(struct GBTimer*, GBRegisterTAC tac);
+void GBTimerUpdateTIMA(struct GBTimer* timer);
 
 #endif