From b5eea012cc6e5785a6aa40c5d9ad1592d67f85c7 Mon Sep 17 00:00:00 2001
From: Lior Halphon <LIJI32@gmail.com>
Date: Sat, 5 Feb 2022 17:43:48 +0200
Subject: [PATCH] STAT reads 0 during mode 2 if DMA is active

---
 Core/display.c | 3 +++
 Core/memory.c  | 5 +++++
 2 files changed, 8 insertions(+)

diff --git a/Core/display.c b/Core/display.c
index 09991d3..a3fded5 100644
--- a/Core/display.c
+++ b/Core/display.c
@@ -397,6 +397,9 @@ void GB_set_light_temperature(GB_gameboy_t *gb, double temperature)
 void GB_STAT_update(GB_gameboy_t *gb)
 {
     if (!(gb->io_registers[GB_IO_LCDC] & 0x80)) return;
+    if (GB_is_dma_active(gb) && (gb->io_registers[GB_IO_STAT] & 3) == 2) {
+        gb->io_registers[GB_IO_STAT] &= ~3;
+    }
     
     bool previous_interrupt_line = gb->stat_interrupt_line;
     /* Set LY=LYC bit */
diff --git a/Core/memory.c b/Core/memory.c
index 0ad9c84..19a4121 100644
--- a/Core/memory.c
+++ b/Core/memory.c
@@ -1471,6 +1471,7 @@ static void write_high_memory(GB_gameboy_t *gb, uint16_t addr, uint8_t value)
                 gb->dma_current_dest = 0xFF;
                 gb->dma_current_src = value << 8;
                 gb->io_registers[GB_IO_DMA] = value;
+                GB_STAT_update(gb);
                 return;
             case GB_IO_SVBK:
                 if (gb->cgb_mode || (GB_is_cgb(gb) && !gb->boot_rom_finished)) {
@@ -1701,6 +1702,10 @@ void GB_dma_run(GB_gameboy_t *gb)
         cycles -= 4;
         if (gb->dma_current_dest >= 0xa0) {
             gb->dma_current_dest++;
+            if (gb->display_state == 8) {
+                gb->io_registers[GB_IO_STAT] |= 2;
+                GB_STAT_update(gb);
+            }
             break;
         }
         if (unlikely(gb->hdma_in_progress && (gb->hdma_steps_left > 1 || (gb->hdma_current_dest & 0xF) != 0xF))) {