DP_GUI_MASTER_CNTL aliases several fields from DP_DATATYPE and DP_MIX.
These were being written correctly but not returned on a read of
DP_GUI_MASTER_CNTL.

Signed-off-by: Chad Jablonski <chad@jablonski.xyz>
Reviewed-by: BALATON Zoltan <balaton@eik.bme.hu>
---
 hw/display/ati.c      | 8 +++++++-
 hw/display/ati_regs.h | 5 +++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/hw/display/ati.c b/hw/display/ati.c
index 777a6b0a2e..028efd13e1 100644
--- a/hw/display/ati.c
+++ b/hw/display/ati.c
@@ -460,7 +460,13 @@ static uint64_t ati_mm_read(void *opaque, hwaddr addr, unsigned int size)
         val = s->regs.dst_y;
         break;
     case DP_GUI_MASTER_CNTL:
-        val = s->regs.dp_gui_master_cntl;
+        /* DP_GUI_MASTER_CNTL aliases fields from DP_MIX and DP_DATATYPE */
+        val = s->regs.dp_gui_master_cntl |
+              ((s->regs.dp_datatype & DP_BRUSH_DATATYPE) >> 4) |
+              ((s->regs.dp_datatype & DP_DST_DATATYPE) << 8) |
+              ((s->regs.dp_datatype & DP_SRC_DATATYPE) >> 4) |
+              (s->regs.dp_mix & DP_ROP3) |
+              ((s->regs.dp_mix & DP_SRC_SOURCE) << 16);
         break;
     case SRC_OFFSET:
         val = s->regs.src_offset;
diff --git a/hw/display/ati_regs.h b/hw/display/ati_regs.h
index d7127748ff..0a0825db04 100644
--- a/hw/display/ati_regs.h
+++ b/hw/display/ati_regs.h
@@ -386,6 +386,9 @@
 #define DST_16BPP                               0x00000004
 #define DST_24BPP                               0x00000005
 #define DST_32BPP                               0x00000006
+#define DP_DST_DATATYPE                         0x0000000f
+#define DP_BRUSH_DATATYPE                       0x00000f00
+#define DP_SRC_DATATYPE                         0x00030000
 
 #define BRUSH_SOLIDCOLOR                        0x00000d00
 
@@ -437,6 +440,8 @@
 #define DP_SRC_RECT                             0x00000200
 #define DP_SRC_HOST                             0x00000300
 #define DP_SRC_HOST_BYTEALIGN                   0x00000400
+#define DP_SRC_SOURCE                           0x00000700
+#define DP_ROP3                                 0x00ff0000
 
 /* LVDS_GEN_CNTL constants */
 #define LVDS_BL_MOD_LEVEL_MASK                  0x0000ff00
-- 
2.52.0