From e88697c7733954353a56a4cba50157e72a7de2c3 Mon Sep 17 00:00:00 2001
From: condret <condr3t@protonmail.com>
Date: Fri, 1 Nov 2024 02:24:47 +0100
Subject: [PATCH] Immplement oam_scan

---
 include/gb.h | 27 +++++++++++++++++----------
 io/dma.c     |  4 ++--
 io/ppu.c     | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 70 insertions(+), 12 deletions(-)

diff --git a/include/gb.h b/include/gb.h
index fcc090a..ced4190 100644
--- a/include/gb.h
+++ b/include/gb.h
@@ -87,24 +87,30 @@ enum {
 	GB_PPU_N_REGS,
 };
 
+enum {
+	GB_PPU_STAT_MODE_HBLANK = 0,
+	GB_PPU_STAT_MODE_VBLANK,
+	GB_PPU_STAT_MODE_OAM_SCAN,
+	GB_PPU_STAT_MODE_RENDER,
+};
+
+#define	GB_PPU_STAT_MODE_MASK	0x3
+
+typedef struct oam_scan_table {
+	ut16 data[10];	//low byte is x coordinate of sprite; high byte is addr of entry (0xffe0 + high byte)
+	ut8 n_entries;	//max 10
+	ut8 addr;
+} OAMScanTable;
+
 typedef struct gb_dmg_ppu_t {
 	GBPixBuf *pixbuf;
 	ut64 seek;
 	ut8 buf[GB_PPU_N_REGS];
+	OAMScanTable ost;
 	int reg_fd;
 	int vram_fd;
 } GBPPU;
 
-//these are in STAT
-#define	GB_PPU_MODE0	0
-#define	GB_PPU_MODE1	1
-#define	GB_PPU_MODE2	2
-#define	GB_PPU_MODE3	3
-#define	GB_PPU_MODE_MASK	3
-
-//this is in seek
-#define	GB_PPU_DOUBLE_SPEED	0x10000
-
 typedef struct gameboy_t {
 	RIO *io;
 	RArch *arch;
@@ -114,6 +120,7 @@ typedef struct gameboy_t {
 	GBPPU *ppu;
 	ut64 addr;
 	int cartrigde_fd;
+	bool double_speed;
 } GB;
 
 GBPPU *gb_ppu_open (RIO *io, SDL_Renderer *renderer);
diff --git a/io/dma.c b/io/dma.c
index 7b3fe6f..99f814c 100644
--- a/io/dma.c
+++ b/io/dma.c
@@ -60,10 +60,10 @@ static int __bus_write(RIO *io, RIODesc *desc, const ut8 *buf, int len) {
 	int _len = R_MIN (len, 0xa0 - ((ut32)dma->dst + (st32)dma->frontrun));
 //	memcpy (buf, &dma->buf[dma->dst + dma->frontrun], _len);
 	dma->frontrun += _len;
-#if 0
+#if 1
 	if (len != _len) {
 		ut64 vseek = r_io_p2v (io, seek + _len);
-		r_io_bank_write_at (io, dma->default_bank_id, &buf[_len], len - _len)
+		r_io_bank_write_at (io, dma->default_bank_id, vseek, &buf[_len], len - _len);
 	}
 #endif
 	seek += len;
diff --git a/io/ppu.c b/io/ppu.c
index ff05720..353665f 100644
--- a/io/ppu.c
+++ b/io/ppu.c
@@ -124,7 +124,58 @@ GBPPU *gb_ppu_open (RIO *io, SDL_Renderer *renderer) {
 	return ppu;
 }
 
+static ut32 gb_ppu_oam_scan_update (GB *gb, ut32 cycles) {
+	if (gb->ppu->ost.addr >= 0xa0) {
+		gb->ppu->ost.addr = 0;
+		gb->ppu->ost.n_entries = 0;
+	}
+	if (cycles & 0x1) {
+		R_LOG_WARN ("Odd amount of cycles");
+	}
+	if (gb->dma->seek & GB_DMA_ACTIVE) {
+		const ut8 running_cycles = R_MIN (cycles, (0xa0 - gb->ppu->ost.addr) >> 1);
+		//every oam entry costs 2 cycles
+		gb->ppu->ost.addr += running_cycles << 1;
+		cycles -= running_cycles;
+		goto beach;
+	}
+	const ut8 height = gb->ppu->buf[GB_PPU_LCDC] & 0x3? 16: 8;
+	const ut8 ly = gb->ppu->buf[GB_PPU_LY] + 16; 
+	while (cycles && gb->ppu->ost.addr <= 0xa0) {
+		if (gb->ppu->ost.n_entries < 10) {
+			ut8 yx[2];
+			r_io_fd_read_at (gb->io, gb->dma->oam_fd, (ut64)gb->ppu->ost.addr, yx, 2);
+			if ((yx[0] <= ly) && (ly < (yx[0] + height))) {
+				gb->ppu->ost.data[gb->ppu->ost.n_entries] =
+					(gb->ppu->ost.addr << 8) | yx[1];
+				gb->ppu->ost.n_entries++;
+			}
+		}
+		gb->ppu->ost.addr += 4;
+		cycles -= 2;
+	}
+beach:
+	if (gb->ppu->ost.addr == 0xa0) {
+		//indicate next mode
+		gb->ppu->buf[GB_PPU_STAT] |= GB_PPU_STAT_MODE_RENDER;
+	}
+	return cycles;
+}
+
 void gb_ppu_update (GB *gb, ut32 cycles) {
+	while (cycles) {
+		switch (gb->ppu->buf[GB_PPU_STAT] & GB_PPU_STAT_MODE_MASK) {
+		case GB_PPU_STAT_MODE_OAM_SCAN:
+			cycles = gb_ppu_oam_scan_update (gb, cycles);
+			break;
+		case GB_PPU_STAT_MODE_RENDER:
+			break;
+		case GB_PPU_STAT_MODE_HBLANK:
+			break;
+		case GB_PPU_STAT_MODE_VBLANK:
+			break;
+		}
+	}
 	//TODO
 }