305 lines
9.4 KiB
Zig
305 lines
9.4 KiB
Zig
const std = @import("std");
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const io = @import("bus/io.zig");
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const EventKind = @import("scheduler.zig").EventKind;
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const Scheduler = @import("scheduler.zig").Scheduler;
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const Bit = @import("bitfield").Bit;
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const Bitfield = @import("bitfield").Bitfield;
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const Allocator = std.mem.Allocator;
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pub const width = 240;
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pub const height = 160;
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pub const framebuf_pitch = width * @sizeOf(u16);
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pub const Ppu = struct {
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const Self = @This();
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// Registers
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bg0: Background,
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bg1: Background,
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bg2: Background,
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bg3: Background,
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dispcnt: io.DisplayControl,
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dispstat: io.DisplayStatus,
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vcount: io.VCount,
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vram: Vram,
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palette: Palette,
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oam: Oam,
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sched: *Scheduler,
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framebuf: []u8,
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alloc: Allocator,
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pub fn init(alloc: Allocator, sched: *Scheduler) !Self {
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// Queue first Hblank
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sched.push(.Draw, sched.tick + (240 * 4));
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const framebuf = try alloc.alloc(u8, framebuf_pitch * height);
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std.mem.set(u8, framebuf, 0);
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return Self{
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.vram = try Vram.init(alloc),
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.palette = try Palette.init(alloc),
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.oam = try Oam.init(alloc),
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.sched = sched,
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.framebuf = framebuf,
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.alloc = alloc,
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// Registers
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.bg0 = Background.init(),
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.bg1 = Background.init(),
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.bg2 = Background.init(),
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.bg3 = Background.init(),
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.dispcnt = .{ .raw = 0x0000 },
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.dispstat = .{ .raw = 0x0000 },
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.vcount = .{ .raw = 0x0000 },
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};
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}
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pub fn deinit(self: Self) void {
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self.alloc.free(self.framebuf);
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self.vram.deinit();
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self.palette.deinit();
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}
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pub fn drawScanline(self: *Self) void {
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const bg_mode = self.dispcnt.bg_mode.read();
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const scanline = self.vcount.scanline.read();
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switch (bg_mode) {
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0x0 => {
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// A Tile is always 8x8 pixels
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// Mode 0 Implementation Assuming:
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// - Scrolling isn't a thing
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// - Bill Gates said we'll never need more than BG0
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// Write to this Scanline once we're done
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const start = framebuf_pitch * @as(usize, scanline);
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var scanline_buf = std.mem.zeroes([framebuf_pitch]u8);
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// These we can probably move to top level?
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const charblock_len: u32 = 0x4000;
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const screenblock_len: u32 = 0x800;
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const cbb: u2 = self.bg0.cnt.char_base.read(); // Char Block Base
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const sbb: u5 = self.bg0.cnt.screen_base.read(); // Screen Block Base
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const is_8bpp: bool = self.bg0.cnt.palette_type.read(); // Colour Mode
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const size: u2 = self.bg0.cnt.screen_size.read(); // Background Size
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// 0x0600_000 is implied because we can access VRAM without the Bus
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const char_base: u32 = charblock_len * @as(u32, cbb);
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const screen_base: u32 = screenblock_len * @as(u32, sbb);
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const y = @as(u32, scanline);
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var x: u32 = 0;
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while (x < width) : (x += 1) {
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const entry_addr = screen_base + tilemapIndex(size, x, y);
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const entry = @bitCast(ScreenEntry, @as(u16, self.vram.buf[entry_addr + 1]) << 8 | @as(u16, self.vram.buf[entry_addr]));
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const tile_id: u32 = entry.tile_id.read();
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const px_y = if (entry.h_flip.read()) 7 - (y % 8) else y % 8;
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const px_x = if (entry.v_flip.read()) 7 - (x % 8) else x % 8;
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const tile_addr = char_base + if (is_8bpp) 0x40 * tile_id + 0x8 * px_y else 0x20 * tile_id + 0x4 * px_y;
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var tile = self.vram.buf[tile_addr + if (is_8bpp) px_x else px_x >> 1];
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tile = if (px_x & 1 == 1) tile >> 4 else tile & 0xF;
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const pal_bank: u8 = @as(u8, entry.palette_bank.read()) << 4;
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const colour = pal_bank | tile;
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std.mem.copy(u8, scanline_buf[x * 2 ..][0..2], self.palette.buf[colour * 2 ..][0..2]);
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}
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std.mem.copy(u8, self.framebuf[start..][0..framebuf_pitch], &scanline_buf);
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},
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0x3 => {
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const start = framebuf_pitch * @as(usize, scanline);
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std.mem.copy(u8, self.framebuf[start..][0..framebuf_pitch], self.vram.buf[start..][0..framebuf_pitch]);
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},
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0x4 => {
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const select = self.dispcnt.frame_select.read();
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const vram_start = width * @as(usize, scanline);
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const buf_start = vram_start * @sizeOf(u16);
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const start = vram_start + if (select) 0xA000 else @as(usize, 0);
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const end = start + width; // Each Entry is only a byte long
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// Render Current Scanline
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for (self.vram.buf[start..end]) |byte, i| {
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const id = byte * 2;
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const j = i * @sizeOf(u16);
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std.mem.copy(u8, self.framebuf[(buf_start + j)..][0..2], self.palette.buf[id..][0..2]);
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}
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},
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else => std.debug.panic("[PPU] TODO: Implement BG Mode {}", .{bg_mode}),
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}
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}
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fn tilemapIndex(size: u2, x: u32, y: u32) u32 {
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return switch (size) {
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0 => (((y % 256) / 8) * 64) + (((x % 256) / 8) * 2),
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1 => (((y % 256) / 8) * 64) + (((x % 256) / 8) * 2),
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else => std.debug.panic("tile size {}", .{size}),
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};
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}
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};
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const Palette = struct {
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const Self = @This();
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buf: []u8,
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alloc: Allocator,
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fn init(alloc: Allocator) !Self {
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const buf = try alloc.alloc(u8, 0x400);
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std.mem.set(u8, buf, 0);
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return Self{
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.buf = buf,
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.alloc = alloc,
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};
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}
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fn deinit(self: Self) void {
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self.alloc.free(self.buf);
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}
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pub fn get32(self: *const Self, idx: usize) u32 {
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return (@as(u32, self.get16(idx + 2)) << 16) | @as(u32, self.get16(idx));
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}
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pub fn set32(self: *Self, idx: usize, word: u32) void {
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self.set16(idx + 2, @truncate(u16, word >> 16));
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self.set16(idx, @truncate(u16, word));
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}
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pub fn get16(self: *const Self, idx: usize) u16 {
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return (@as(u16, self.buf[idx + 1]) << 8) | @as(u16, self.buf[idx]);
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}
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pub fn set16(self: *Self, idx: usize, halfword: u16) void {
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self.buf[idx + 1] = @truncate(u8, halfword >> 8);
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self.buf[idx] = @truncate(u8, halfword);
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}
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pub fn get8(self: *const Self, idx: usize) u8 {
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return self.buf[idx];
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}
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};
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const Vram = struct {
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const Self = @This();
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buf: []u8,
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alloc: Allocator,
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fn init(alloc: Allocator) !Self {
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const buf = try alloc.alloc(u8, 0x18000);
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std.mem.set(u8, buf, 0);
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return Self{
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.buf = buf,
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.alloc = alloc,
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};
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}
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fn deinit(self: Self) void {
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self.alloc.free(self.buf);
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}
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pub fn get32(self: *const Self, idx: usize) u32 {
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return (@as(u32, self.get16(idx + 2)) << 16) | @as(u32, self.get16(idx));
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}
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pub fn set32(self: *Self, idx: usize, word: u32) void {
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self.set16(idx + 2, @truncate(u16, word >> 16));
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self.set16(idx, @truncate(u16, word));
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}
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pub fn get16(self: *const Self, idx: usize) u16 {
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return (@as(u16, self.buf[idx + 1]) << 8) | @as(u16, self.buf[idx]);
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}
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pub fn set16(self: *Self, idx: usize, halfword: u16) void {
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self.buf[idx + 1] = @truncate(u8, halfword >> 8);
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self.buf[idx] = @truncate(u8, halfword);
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}
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pub fn get8(self: *const Self, idx: usize) u8 {
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return self.buf[idx];
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}
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};
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const Oam = struct {
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const Self = @This();
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buf: []u8,
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alloc: Allocator,
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fn init(alloc: Allocator) !Self {
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const buf = try alloc.alloc(u8, 0x400);
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std.mem.set(u8, buf, 0);
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return Self{
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.buf = buf,
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.alloc = alloc,
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};
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}
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pub fn get32(self: *const Self, idx: usize) u32 {
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return (@as(u32, self.buf[idx + 3]) << 24) | (@as(u32, self.buf[idx + 2]) << 16) | (@as(u32, self.buf[idx + 1]) << 8) | (@as(u32, self.buf[idx]));
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}
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pub fn set32(self: *Self, idx: usize, word: u32) void {
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self.buf[idx + 3] = @truncate(u8, word >> 24);
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self.buf[idx + 2] = @truncate(u8, word >> 16);
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self.buf[idx + 1] = @truncate(u8, word >> 8);
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self.buf[idx] = @truncate(u8, word);
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}
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pub fn get16(self: *const Self, idx: usize) u16 {
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return (@as(u16, self.buf[idx + 1]) << 8) | @as(u16, self.buf[idx]);
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}
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pub fn set16(self: *Self, idx: usize, halfword: u16) void {
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self.buf[idx + 1] = @truncate(u8, halfword >> 8);
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self.buf[idx] = @truncate(u8, halfword);
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}
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pub fn get8(self: *const Self, idx: usize) u8 {
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return self.buf[idx];
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}
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};
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const Background = struct {
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const Self = @This();
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/// Read / Write
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cnt: io.BackgroundControl,
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/// Write Only
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hofs: io.BackgroundOffset,
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/// Write Only
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vofs: io.BackgroundOffset,
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fn init() Self {
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return .{
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.cnt = .{ .raw = 0x0000 },
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.hofs = .{ .raw = 0x0000 },
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.vofs = .{ .raw = 0x0000 },
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};
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}
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};
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const ScreenEntry = extern union {
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tile_id: Bitfield(u16, 0, 10),
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h_flip: Bit(u16, 10),
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v_flip: Bit(u16, 11),
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palette_bank: Bitfield(u16, 12, 4),
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raw: u16,
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};
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