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vga: reindent memory access code
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The next patch will reuse latched memory access in text modes.  Start with
a patch that moves the latched access code out of the "if".

Best reviewed with "git diff -b".

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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@bonzini
bonzini committed Jan 18, 2024
1 parent 4d6c310 commit ae9d71a
Showing 1 changed file with 105 additions and 96 deletions.
201 changes: 105 additions & 96 deletions hw/display/vga.c
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Original file line number Diff line number Diff line change
Expand Up @@ -815,37 +815,41 @@ uint32_t vga_mem_readb(VGACommonState *s, hwaddr addr)
}

if (sr(s, VGA_SEQ_MEMORY_MODE) & VGA_SR04_CHN_4M) {
/* chain 4 mode : simplest access */
/* chain 4 mode : simplest access (but it should use the same
* algorithms as below; see e.g. vga_mem_writeb's plane mask check).
*/
assert(addr < s->vram_size);
ret = s->vram_ptr[addr];
} else if (s->gr[VGA_GFX_MODE] & 0x10) {
return s->vram_ptr[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;
}
ret = s->vram_ptr[addr];
} else {
/* standard VGA latched access */
if (addr * sizeof(uint32_t) >= s->vram_size) {
return 0xff;
}
s->latch = ((uint32_t *)s->vram_ptr)[addr];
return s->vram_ptr[addr];
}

if (!(s->gr[VGA_GFX_MODE] & 0x08)) {
/* read mode 0 */
plane = s->gr[VGA_GFX_PLANE_READ];
ret = GET_PLANE(s->latch, plane);
} else {
/* read mode 1 */
ret = (s->latch ^ mask16[s->gr[VGA_GFX_COMPARE_VALUE]]) &
mask16[s->gr[VGA_GFX_COMPARE_MASK]];
ret |= ret >> 16;
ret |= ret >> 8;
ret = (~ret) & 0xff;
}
/* standard VGA latched access */
plane = s->gr[VGA_GFX_PLANE_READ];
if (addr * sizeof(uint32_t) >= s->vram_size) {
return 0xff;
}
s->latch = ((uint32_t *)s->vram_ptr)[addr];
if (!(s->gr[VGA_GFX_MODE] & 0x08)) {
/* read mode 0 */
ret = GET_PLANE(s->latch, plane);
} else {
/* read mode 1 */
ret = (s->latch ^ mask16[s->gr[VGA_GFX_COMPARE_VALUE]]) &
mask16[s->gr[VGA_GFX_COMPARE_MASK]];
ret |= ret >> 16;
ret |= ret >> 8;
ret = (~ret) & 0xff;
}

return ret;
}

Expand Down Expand Up @@ -895,7 +899,10 @@ void vga_mem_writeb(VGACommonState *s, hwaddr addr, uint32_t val)
s->plane_updated |= mask; /* only used to detect font change */
memory_region_set_dirty(&s->vram, addr, 1);
}
} else if (s->gr[VGA_GFX_MODE] & 0x10) {
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);
Expand All @@ -911,84 +918,86 @@ void vga_mem_writeb(VGACommonState *s, hwaddr addr, uint32_t val)
s->plane_updated |= mask; /* only used to detect font change */
memory_region_set_dirty(&s->vram, addr, 1);
}
} else {
/* standard VGA latched access */
write_mode = s->gr[VGA_GFX_MODE] & 3;
switch(write_mode) {
default:
case 0:
/* rotate */
b = s->gr[VGA_GFX_DATA_ROTATE] & 7;
val = ((val >> b) | (val << (8 - b))) & 0xff;
val |= val << 8;
val |= val << 16;

/* apply set/reset mask */
set_mask = mask16[s->gr[VGA_GFX_SR_ENABLE]];
val = (val & ~set_mask) |
(mask16[s->gr[VGA_GFX_SR_VALUE]] & set_mask);
bit_mask = s->gr[VGA_GFX_BIT_MASK];
break;
case 1:
val = s->latch;
goto do_write;
case 2:
val = mask16[val & 0x0f];
bit_mask = s->gr[VGA_GFX_BIT_MASK];
break;
case 3:
/* rotate */
b = s->gr[VGA_GFX_DATA_ROTATE] & 7;
val = (val >> b) | (val << (8 - b));
return;
}

bit_mask = s->gr[VGA_GFX_BIT_MASK] & val;
val = mask16[s->gr[VGA_GFX_SR_VALUE]];
break;
}
mask = sr(s, VGA_SEQ_PLANE_WRITE);

/* apply logical operation */
func_select = s->gr[VGA_GFX_DATA_ROTATE] >> 3;
switch(func_select) {
case 0:
default:
/* nothing to do */
break;
case 1:
/* and */
val &= s->latch;
break;
case 2:
/* or */
val |= s->latch;
break;
case 3:
/* xor */
val ^= s->latch;
break;
}
/* standard VGA latched access */
write_mode = s->gr[VGA_GFX_MODE] & 3;
switch(write_mode) {
default:
case 0:
/* rotate */
b = s->gr[VGA_GFX_DATA_ROTATE] & 7;
val = ((val >> b) | (val << (8 - b))) & 0xff;
val |= val << 8;
val |= val << 16;

/* apply set/reset mask */
set_mask = mask16[s->gr[VGA_GFX_SR_ENABLE]];
val = (val & ~set_mask) |
(mask16[s->gr[VGA_GFX_SR_VALUE]] & set_mask);
bit_mask = s->gr[VGA_GFX_BIT_MASK];
break;
case 1:
val = s->latch;
goto do_write;
case 2:
val = mask16[val & 0x0f];
bit_mask = s->gr[VGA_GFX_BIT_MASK];
break;
case 3:
/* rotate */
b = s->gr[VGA_GFX_DATA_ROTATE] & 7;
val = (val >> b) | (val << (8 - b));

/* apply bit mask */
bit_mask |= bit_mask << 8;
bit_mask |= bit_mask << 16;
val = (val & bit_mask) | (s->latch & ~bit_mask);

do_write:
/* mask data according to sr[2] */
mask = sr(s, VGA_SEQ_PLANE_WRITE);
s->plane_updated |= mask; /* only used to detect font change */
write_mask = mask16[mask];
if (addr * sizeof(uint32_t) >= s->vram_size) {
return;
}
((uint32_t *)s->vram_ptr)[addr] =
(((uint32_t *)s->vram_ptr)[addr] & ~write_mask) |
(val & write_mask);
bit_mask = s->gr[VGA_GFX_BIT_MASK] & val;
val = mask16[s->gr[VGA_GFX_SR_VALUE]];
break;
}

/* apply logical operation */
func_select = s->gr[VGA_GFX_DATA_ROTATE] >> 3;
switch(func_select) {
case 0:
default:
/* nothing to do */
break;
case 1:
/* and */
val &= s->latch;
break;
case 2:
/* or */
val |= s->latch;
break;
case 3:
/* xor */
val ^= s->latch;
break;
}

/* apply bit mask */
bit_mask |= bit_mask << 8;
bit_mask |= bit_mask << 16;
val = (val & bit_mask) | (s->latch & ~bit_mask);

do_write:
/* mask data according to sr[2] */
s->plane_updated |= mask; /* only used to detect font change */
write_mask = mask16[mask];
if (addr * sizeof(uint32_t) >= s->vram_size) {
return;
}
((uint32_t *)s->vram_ptr)[addr] =
(((uint32_t *)s->vram_ptr)[addr] & ~write_mask) |
(val & write_mask);
#ifdef DEBUG_VGA_MEM
printf("vga: latch: [0x" HWADDR_FMT_plx "] mask=0x%08x val=0x%08x\n",
addr * 4, write_mask, val);
printf("vga: latch: [0x" HWADDR_FMT_plx "] mask=0x%08x val=0x%08x\n",
addr * 4, write_mask, val);
#endif
memory_region_set_dirty(&s->vram, addr << 2, sizeof(uint32_t));
}
memory_region_set_dirty(&s->vram, addr << 2, sizeof(uint32_t));
}

typedef void *vga_draw_line_func(VGACommonState *s1, uint8_t *d,
Expand Down

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