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vga: use latches in odd/even mode too

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Jazz Jackrabbit uses odd/even mode with 256-color graphics.  This is
probably so that it can do very fast blitting with a decent resolution
(two pixels, compared to four pixels for "regular" mode X).

Accesses still use all planes (reads go to the latches and the game uses
read mode 1 so that the CPU always gets 0xFF; writes use the plane mask
register because the game sets bit 2 of the sequencer's memory mode
register).  For this to work, QEMU needs to use the code for latched
memory accesses in odd/even mode.  The only difference between odd/even
mode and "regular" planar mode is how the plane is computed in read mode
0, and how the planes are masked if the aforementioned bit 2 is reset.

It is almost enough to fix the game.  You also need to honor byte/word
mode selection, which is done in the next patch.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2014-12-30 22:42:06 +01:00
parent ae9d71a003
commit 3f83435042
1 changed files with 13 additions and 27 deletions
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40
hw/display/vga.c
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@ -825,15 +825,12 @@ uint32_t vga_mem_readb(VGACommonState *s, hwaddr addr)
if (s->gr[VGA_GFX_MODE] & 0x10) {
/* odd/even mode (aka text mode mapping) */
plane = (s->gr[VGA_GFX_PLANE_READ] & 2) | (addr & 1);
addr = ((addr & ~1) << 1) | plane;
if (addr >= s->vram_size) {
return 0xff;
}
return s->vram_ptr[addr];
}
addr >>= 1;
} else {
/* standard VGA latched access */
plane = s->gr[VGA_GFX_PLANE_READ];
}
if (addr * sizeof(uint32_t) >= s->vram_size) {
return 0xff;
}
@ -886,11 +883,12 @@ void vga_mem_writeb(VGACommonState *s, hwaddr addr, uint32_t val)
break;
}
mask = sr(s, VGA_SEQ_PLANE_WRITE);
if (sr(s, VGA_SEQ_MEMORY_MODE) & VGA_SR04_CHN_4M) {
/* chain 4 mode : simplest access */
plane = addr & 3;
mask = (1 << plane);
if (sr(s, VGA_SEQ_PLANE_WRITE) & mask) {
mask &= (1 << plane);
if (mask) {
assert(addr < s->vram_size);
s->vram_ptr[addr] = val;
#ifdef DEBUG_VGA_MEM
@ -902,26 +900,14 @@ void vga_mem_writeb(VGACommonState *s, hwaddr addr, uint32_t val)
return;
}
if (s->gr[VGA_GFX_MODE] & 0x10) {
/* odd/even mode (aka text mode mapping) */
plane = (s->gr[VGA_GFX_PLANE_READ] & 2) | (addr & 1);
mask = (1 << plane);
if (sr(s, VGA_SEQ_PLANE_WRITE) & mask) {
addr = ((addr & ~1) << 1) | plane;
if (addr >= s->vram_size) {
return;
}
s->vram_ptr[addr] = val;
#ifdef DEBUG_VGA_MEM
printf("vga: odd/even: [0x" HWADDR_FMT_plx "]\n", addr);
#endif
s->plane_updated |= mask; /* only used to detect font change */
memory_region_set_dirty(&s->vram, addr, 1);
}
return;
if ((sr(s, VGA_SEQ_MEMORY_MODE) & VGA_SR04_SEQ_MODE) == 0) {
mask &= (addr & 1) ? 0x0a : 0x05;
}
mask = sr(s, VGA_SEQ_PLANE_WRITE);
if (s->gr[VGA_GFX_MODE] & 0x10) {
/* odd/even mode (aka text mode mapping) */
addr >>= 1;
}
/* standard VGA latched access */
write_mode = s->gr[VGA_GFX_MODE] & 3;