From: Chad Jablonski <chad@jablonski.xyz>

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 <chad@jablonski.xyz>
Reviewed-by: BALATON Zoltan <balaton@eik.bme.hu>
Message-ID: <20260303024730.1489136-5-chad@jablonski.xyz>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
---
 hw/display/ati.c    |  9 +++++++++
 hw/display/ati_2d.c | 13 ++++---------
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/hw/display/ati.c b/hw/display/ati.c
index 028efd13e19..ce23e5e48b9 100644
--- a/hw/display/ati.c
+++ b/hw/display/ati.c
@@ -868,6 +868,15 @@ static void ati_mm_write(void *opaque, hwaddr addr,
         s->regs.dp_datatype = (data & 0x0f00) >> 8 | (data & 0x30f0) << 4 |
                               (data & 0x4000) << 16;
         s->regs.dp_mix = (data & GMC_ROP3_MASK) | (data & 0x7000000) >> 16;
+
+        if (!(data & GMC_SRC_PITCH_OFFSET_CNTL)) {
+            s->regs.src_offset = s->regs.default_offset;
+            s->regs.src_pitch = s->regs.default_pitch;
+        }
+        if (!(data & GMC_DST_PITCH_OFFSET_CNTL)) {
+            s->regs.dst_offset = s->regs.default_offset;
+            s->regs.dst_pitch = s->regs.default_pitch;
+        }
         break;
     case DST_WIDTH_X:
         s->regs.dst_x = data & 0x3fff;
diff --git a/hw/display/ati_2d.c b/hw/display/ati_2d.c
index 309bb5ccb6c..a8c4c534b94 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;
-- 
2.53.0