gba: handle 8bit writes to vram

ignore 8bit writes to obj and oam, and duplicate bits for bg and palette
memory, as per gbatek.

thanks aiju for helping with the implementation.

diff --git a/sys/src/games/gba/mem.c b/sys/src/games/gba/mem.c
index c5a56abbb6d0ca368e93c47fdb265ab0d3be8087..500123b4e7aef0f0cd299f3c90901b25eca70b55 100644 (file)
--- a/sys/src/games/gba/mem.c
+++ b/sys/src/games/gba/mem.c
@@ -315,6 +315,11 @@ memwrite(u32int a, u32int v, int n)
                return;
        case 5:
                b = a & sizeof(pram) - 1;
+               if(n == 1){
+                       b &= ~1;
+                       n = 2;
+                       v |= v << 8;
+               }
                cyc += (n+1) >> 1;
                ar16write(pram + b/2, b & 1, v, n);
                return;
@@ -322,13 +327,20 @@ memwrite(u32int a, u32int v, int n)
                b = a & 128*KB - 1;
                if(b >= 64*KB)
                        b &= ~(32*KB);
+               if(n == 1 && ((reg[DISPCNT] & 7) > 2 && b < 80*KB || b < 64*KB)){
+                       b &= ~1;
+                       n = 2;
+                       v |= v << 8;
+               }
                cyc += (n+1) >> 1;
-               arwrite(vram + b, v, n);
+               if(n != 1)
+                       arwrite(vram + b, v, n);
                return;
        case 7:
                b = a & sizeof(oam) - 1;
                cyc++;
-               ar16write(oam + b/2, b & 1, v, n);
+               if(n != 1)
+                       ar16write(oam + b/2, b & 1, v, n);
                return;
        case 8: case 9: case 10: case 11: case 12: case 13:
                if(backup == EEPROM){