From 76b881c2e153e164485814257fee472572dd8482 Mon Sep 17 00:00:00 2001
From: Lior Halphon <LIJI32@gmail.com>
Date: Wed, 2 Feb 2022 23:01:38 +0200
Subject: [PATCH] More accurate HDMA during halt

---
 Core/display.c  | 2 +-
 Core/sm83_cpu.c | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/Core/display.c b/Core/display.c
index fc61dda..35ac8df 100644
--- a/Core/display.c
+++ b/Core/display.c
@@ -1773,7 +1773,7 @@ skip_slow_mode_3:
             GB_SLEEP(gb, display, 33, 2);
             gb->cgb_palettes_blocked = !gb->cgb_double_speed;
             
-            if (gb->hdma_on_hblank) {
+            if (gb->hdma_on_hblank && !gb->halted && !gb->stopped) {
                 gb->hdma_on = true;
             }
             
diff --git a/Core/sm83_cpu.c b/Core/sm83_cpu.c
index b79e4fc..14050af 100644
--- a/Core/sm83_cpu.c
+++ b/Core/sm83_cpu.c
@@ -1617,6 +1617,9 @@ void GB_cpu_run(GB_gameboy_t *gb)
     /* Wake up from HALT mode without calling interrupt code. */
     if (gb->halted && !effective_ime && interrupt_queue) {
         gb->halted = false;
+        if (gb->hdma_on_hblank && (gb->io_registers[GB_IO_STAT] & 3) == 0) {
+            gb->hdma_on = true;
+        }
         gb->dma_cycles = 4;
         GB_dma_run(gb);
         gb->speed_switch_halt_countdown = 0;
@@ -1625,6 +1628,9 @@ void GB_cpu_run(GB_gameboy_t *gb)
     /* Call interrupt */
     else if (effective_ime && interrupt_queue) {
         gb->halted = false;
+        if (gb->hdma_on_hblank && (gb->io_registers[GB_IO_STAT] & 3) == 0) {
+            gb->hdma_on = true;
+        }
         // TODO: verify the timing!
         gb->dma_cycles = 4;
         GB_dma_run(gb);