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fix: resolve bugs in VRAM unpredictable read/writes

This commit is contained in:
Rekai Nyangadzayi Musuka 2022-06-29 03:59:14 -03:00
parent 887bd89668
commit 5d37c212e2
1 changed files with 9 additions and 14 deletions
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23
src/ppu.zig
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@ -658,11 +658,8 @@ const Palette = struct {
switch (T) {
u32, u16 => std.mem.writeIntSliceLittle(T, self.buf[addr..][0..@sizeOf(T)], value),
u8 => {
const halfword: u16 = @as(u16, value) * 0x0101;
// FIXME: I don't think my comment here makes sense?
const weird_addr = addr & ~@as(u32, 1); // *was* 8-bit read so address won't be aligned
std.mem.writeIntSliceLittle(u16, self.buf[weird_addr..(weird_addr + @sizeOf(u16))], halfword);
const align_addr = addr & ~@as(u32, 1); // Aligned to Halfword boundary
std.mem.writeIntSliceLittle(u16, self.buf[align_addr..][0..@sizeOf(u16)], @as(u16, value) * 0x101);
},
else => @compileError("PALRAM: Unsupported write width"),
}
@ -705,21 +702,19 @@ const Vram = struct {
pub fn write(self: *Self, comptime T: type, dispcnt: io.DisplayControl, address: usize, value: T) void {
const mode: u3 = dispcnt.bg_mode.read();
const addr = Self.mirror(address);
const idx = Self.mirror(address);
switch (T) {
u32, u16 => std.mem.writeIntSliceLittle(T, self.buf[addr..][0..@sizeOf(T)], value),
u32, u16 => std.mem.writeIntSliceLittle(T, self.buf[idx..][0..@sizeOf(T)], value),
u8 => {
// Ignore if write is in OBJ
// Ignore write if it falls within the boundaries of OBJ VRAM
switch (mode) {
0, 1, 2 => if (0x0601_0000 <= address and address < 0x0601_8000) return,
else => if (0x0601_4000 <= address and address < 0x0601_8000) return,
0, 1, 2 => if (0x0001_0000 <= idx) return,
else => if (0x0001_4000 <= idx) return,
}
const halfword: u16 = @as(u16, value) * 0x0101;
const weird_addr = addr & ~@as(u32, 1);
std.mem.writeIntSliceLittle(u16, self.buf[weird_addr..(weird_addr + @sizeOf(u16))], halfword);
const align_idx = idx & ~@as(u32, 1); // Aligned to a halfword boundary
std.mem.writeIntSliceLittle(u16, self.buf[align_idx..][0..@sizeOf(u16)], @as(u16, value) * 0x101);
},
else => @compileError("VRAM: Unsupported write width"),
}