On Tue, 18 Nov 2025, Chad Jablonski wrote:
Hardware testing on the Rage 128 confirms that (SRC/DST)_OFFSET,
and (SRC/DST)_PITCH are latched when (SRC/DST)_PITCH_OFFSET_CNTL bits
in DP_GUI_MASTER_CNTL are set to "default".
The earlier approach looked at the state of the (SRC/DST)_PITCH_OFFSET_CNTL
bits when offset and pitch registers were used. This meant that when
(SRC/DST)_PITCH_OFFSET_CNTL was reset to "leave alone" the old values
stored in the registers would return. This is not how the real hardware
works.
Signed-off-by: Chad Jablonski <[email protected]>
---
hw/display/ati.c | 8 ++++++++
hw/display/ati_2d.c | 13 ++++---------
hw/display/ati_regs.h | 10 ++++++++++
3 files changed, 22 insertions(+), 9 deletions(-)
diff --git a/hw/display/ati.c b/hw/display/ati.c
index a2c0302e42..d0fa51f773 100644
--- a/hw/display/ati.c
+++ b/hw/display/ati.c
@@ -888,6 +888,14 @@ static void ati_mm_write(void *opaque, hwaddr addr,
(data & 0x4000) << 16;
s->regs.dp_mix = (data & GMC_ROP3_MASK) | (data & 0x7000000) >> 16;
+ if ((data & GMC_SRC_PITCH_OFFSET_CNTL_MASK) ==
GMC_SRC_PITCH_OFFSET_DEFAULT) {
+ s->regs.src_offset = s->regs.default_offset;
+ s->regs.src_pitch = s->regs.default_pitch;
+ }
+ if ((data & GMC_DST_PITCH_OFFSET_CNTL_MASK) ==
GMC_DST_PITCH_OFFSET_DEFAULT) {
+ s->regs.dst_offset = s->regs.default_offset;
+ s->regs.dst_pitch = s->regs.default_pitch;
+ }
if ((data & GMC_SRC_CLIPPING_MASK) == GMC_SRC_CLIP_DEFAULT) {
s->regs.src_sc_right = s->regs.default_sc_right;
s->regs.src_sc_bottom = s->regs.default_sc_bottom;
diff --git a/hw/display/ati_2d.c b/hw/display/ati_2d.c
index 309bb5ccb6..a8c4c534b9 100644
--- a/hw/display/ati_2d.c
+++ b/hw/display/ati_2d.c
@@ -43,8 +43,6 @@ static int ati_bpp_from_datatype(ATIVGAState *s)
}
}
-#define DEFAULT_CNTL (s->regs.dp_gui_master_cntl & GMC_DST_PITCH_OFFSET_CNTL)
-
void ati_2d_blt(ATIVGAState *s)
{
/* FIXME it is probably more complex than this and may need to be */
@@ -63,13 +61,12 @@ void ati_2d_blt(ATIVGAState *s)
qemu_log_mask(LOG_GUEST_ERROR, "Invalid bpp\n");
return;
}
- int dst_stride = DEFAULT_CNTL ? s->regs.dst_pitch : s->regs.default_pitch;
+ int dst_stride = s->regs.dst_pitch;
if (!dst_stride) {
qemu_log_mask(LOG_GUEST_ERROR, "Zero dest pitch\n");
return;
}
- uint8_t *dst_bits = s->vga.vram_ptr + (DEFAULT_CNTL ?
- s->regs.dst_offset : s->regs.default_offset);
+ uint8_t *dst_bits = s->vga.vram_ptr + s->regs.dst_offset;
if (s->dev_id == PCI_DEVICE_ID_ATI_RAGE128_PF) {
dst_bits += s->regs.crtc_offset & 0x07ffffff;
@@ -97,14 +94,12 @@ void ati_2d_blt(ATIVGAState *s)
s->regs.src_x : s->regs.src_x + 1 - s->regs.dst_width);
unsigned src_y = (s->regs.dp_cntl & DST_Y_TOP_TO_BOTTOM ?
s->regs.src_y : s->regs.src_y + 1 - s->regs.dst_height);
- int src_stride = DEFAULT_CNTL ?
- s->regs.src_pitch : s->regs.default_pitch;
+ int src_stride = s->regs.src_pitch;
if (!src_stride) {
qemu_log_mask(LOG_GUEST_ERROR, "Zero source pitch\n");
return;
}
- uint8_t *src_bits = s->vga.vram_ptr + (DEFAULT_CNTL ?
- s->regs.src_offset : s->regs.default_offset);
+ uint8_t *src_bits = s->vga.vram_ptr + s->regs.src_offset;
if (s->dev_id == PCI_DEVICE_ID_ATI_RAGE128_PF) {
src_bits += s->regs.crtc_offset & 0x07ffffff;
diff --git a/hw/display/ati_regs.h b/hw/display/ati_regs.h
index 2b56b9fb66..02025eef36 100644
--- a/hw/display/ati_regs.h
+++ b/hw/display/ati_regs.h
@@ -402,6 +402,16 @@
#define GMC_WRITE_MASK_SET 0x40000000
#define GMC_DP_CONVERSION_TEMP_6500 0x00000000
+/* DP_GUI_MASTER_CNTL DP_SRC_PITCH_OFFSET named constants */
+#define GMC_SRC_PITCH_OFFSET_CNTL_MASK 0x00000001
+#define GMC_SRC_PITCH_OFFSET_DEFAULT 0x00000000
+#define GMC_SRC_PITCH_OFFSET_LEAVE_ALONE 0x00000001
+
+/* DP_GUI_MASTER_CNTL DP_DST_PITCH_OFFSET named constants */
+#define GMC_DST_PITCH_OFFSET_CNTL_MASK 0x00000002
+#define GMC_DST_PITCH_OFFSET_DEFAULT 0x00000000
+#define GMC_DST_PITCH_OFFSET_LEAVE_ALONE 0x00000002
+
If you're adding these you could remove GMC_SRC_PITCH_OFFSET_CNTL and
GMC_DST_PITCH_OFFSET_CNTL but I think it's simpler to keep those and
not add these long new defines and just test for the bit as was in
DEFAULT_CNTL (s->regs.dp_gui_master_cntl & GMC_DST_PITCH_OFFSET_CNTL) or
because the zero value is actually what matters as
!(s->regs.dp_gui_master_cntl & GMC_DST_PITCH_OFFSET_CNTL) (or == 0 instead
of ! if you think that's more explicit).
Along the same lines in patch 2 you can just add GMC_SRC_CLIPPING and
GMC_DST_CLIPPING as 4 and 8 replacing the unuseful
GMC_{SRC,DST}_CLIP_DEFAULT values and use that the same way instead of the
3 detailed new defines of which only 2 are used.
Regards,
BALATON Zoltan
/* DP_GUI_MASTER_CNTL DP_SRC_CLIPPING named constants */
#define GMC_SRC_CLIPPING_MASK 0x00000004
#define GMC_SRC_CLIP_DEFAULT 0x00000000
