From 1a41957b3c2be23856d63c28aafbbb3b30f51427 Mon Sep 17 00:00:00 2001
From: Lior Halphon <LIJI32@gmail.com>
Date: Mon, 31 Jan 2022 01:02:31 +0200
Subject: [PATCH] LCDOff behavior, basic halt/stop behavior

---
 Core/display.c  | 14 ++++++--------
 Core/gb.h       |  1 +
 Core/memory.c   |  2 ++
 Core/sm83_cpu.c |  6 ------
 4 files changed, 9 insertions(+), 14 deletions(-)

diff --git a/Core/display.c b/Core/display.c
index b36e73b..fc61dda 100644
--- a/Core/display.c
+++ b/Core/display.c
@@ -437,16 +437,14 @@ void GB_lcd_off(GB_gameboy_t *gb)
     gb->display_cycles = 0;
     /* When the LCD is disabled, state is constant */
     
+    if (gb->hdma_on_hblank && (gb->io_registers[GB_IO_STAT] & 3)) {
+        gb->hdma_on = true;
+    }
+    
     /* When the LCD is off, LY is 0 and STAT mode is 0.  */
     gb->io_registers[GB_IO_LY] = 0;
     gb->io_registers[GB_IO_STAT] &= ~3;
-    if (gb->hdma_on_hblank) {
-        gb->hdma_on_hblank = false;
-        gb->hdma_on = false;
-        
-        /* Todo: is this correct? */
-        gb->hdma_steps_left = 0xff;
-    }
+    
     
     gb->oam_read_blocked = false;
     gb->vram_read_blocked = false;
@@ -696,7 +694,7 @@ static inline uint8_t vram_read(GB_gameboy_t *gb, uint16_t addr)
     if (unlikely(gb->vram_ppu_blocked)) {
         return 0xFF;
     }
-    if (unlikely(gb->hdma_on)) {
+    if (unlikely(gb->hdma_in_progress)) {
         gb->addr_for_hdma_conflict = addr;
         return 0;
     }
diff --git a/Core/gb.h b/Core/gb.h
index 6ef3a6c..5827533 100644
--- a/Core/gb.h
+++ b/Core/gb.h
@@ -779,6 +779,7 @@ struct GB_gameboy_internal_s {
         bool tile_sel_glitch;
         bool disable_oam_corruption; // For safe memory reads
         bool in_dma_read;
+        bool hdma_in_progress;
         uint16_t addr_for_hdma_conflict;
                
         GB_gbs_header_t gbs_header;
diff --git a/Core/memory.c b/Core/memory.c
index e87744e..bd50fe2 100644
--- a/Core/memory.c
+++ b/Core/memory.c
@@ -1736,6 +1736,7 @@ void GB_hdma_run(GB_gameboy_t *gb)
     while (gb->hdma_on) {
         uint8_t byte = gb->hdma_open_bus;
         gb->addr_for_hdma_conflict = 0xFFFF;
+        gb->hdma_in_progress = true; // TODO: timing? (affects VRAM reads)
         GB_advance_cycles(gb, cycles);
         
         if (gb->hdma_current_src < 0x8000 ||
@@ -1773,6 +1774,7 @@ void GB_hdma_run(GB_gameboy_t *gb)
             }
         }
     }
+    gb->hdma_in_progress = false; // TODO: timing? (affects VRAM reads)
     if (!gb->cgb_double_speed) {
         GB_advance_cycles(gb, 2);
     }
diff --git a/Core/sm83_cpu.c b/Core/sm83_cpu.c
index 1bf8094..b79e4fc 100644
--- a/Core/sm83_cpu.c
+++ b/Core/sm83_cpu.c
@@ -1580,9 +1580,6 @@ static opcode_t *opcodes[256] = {
 };
 void GB_cpu_run(GB_gameboy_t *gb)
 {
-    if (unlikely(gb->hdma_on && (gb->stopped || gb->halted))) {
-        GB_hdma_run(gb);
-    }
     if (gb->stopped) {
         GB_timing_sync(gb);
         GB_advance_cycles(gb, 4);
@@ -1686,9 +1683,6 @@ void GB_cpu_run(GB_gameboy_t *gb)
         }
         opcodes[opcode](gb, opcode);
     }
-    else if (gb->hdma_on) {
-        GB_hdma_run(gb);
-    }
     
     flush_pending_cycles(gb);
 }