From db57cbb83e573e115ca60f3855b28c264cf2159a Mon Sep 17 00:00:00 2001
From: notaz <notasas@gmail.com>
Date: Fri, 14 Jul 2023 01:20:43 +0300
Subject: [PATCH] handle more GP0 status bits

should help openbios
---
 libpcsxcore/gpu.h         | 13 +++++++------
 libpcsxcore/misc.c        |  2 ++
 libpcsxcore/psxcounters.c | 12 +++++++++---
 3 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/libpcsxcore/gpu.h b/libpcsxcore/gpu.h
index c924b67b..21384e58 100644
--- a/libpcsxcore/gpu.h
+++ b/libpcsxcore/gpu.h
@@ -24,18 +24,19 @@
 #ifndef __GPU_H__
 #define __GPU_H__
 
-#define PSXGPU_LCF     (1<<31)
-#define PSXGPU_nBUSY   (1<<26)
-#define PSXGPU_ILACE   (1<<22)
-#define PSXGPU_DHEIGHT (1<<19)
+#define PSXGPU_LCF     (1u<<31)
+#define PSXGPU_nBUSY   (1u<<26)
+#define PSXGPU_ILACE   (1u<<22)
+#define PSXGPU_DHEIGHT (1u<<19)
+#define PSXGPU_FIELD   (1u<<13)
 
 // both must be set for interlace to work
-#define PSXGPU_ILACE_BITS (PSXGPU_ILACE | PSXGPU_DHEIGHT)
+#define PSXGPU_ILACE_BITS (PSXGPU_ILACE | PSXGPU_DHEIGHT | PSXGPU_FIELD)
 
 #define HW_GPU_STATUS psxHu32ref(0x1814)
 
 // TODO: handle com too
-#define PSXGPU_TIMING_BITS (PSXGPU_LCF | PSXGPU_nBUSY)
+#define PSXGPU_TIMING_BITS (PSXGPU_LCF | PSXGPU_nBUSY | PSXGPU_FIELD)
 
 #define gpuSyncPluginSR() { \
 	HW_GPU_STATUS &= SWAP32(PSXGPU_TIMING_BITS); \
diff --git a/libpcsxcore/misc.c b/libpcsxcore/misc.c
index 022ad6d9..678f2dbf 100644
--- a/libpcsxcore/misc.c
+++ b/libpcsxcore/misc.c
@@ -164,6 +164,8 @@ void BiosLikeGPUSetup()
 
 	for (i = 0; i < sizeof(gpu_data_def) / sizeof(gpu_data_def[0]); i++)
 		GPU_writeData(gpu_data_def[i]);
+
+	HW_GPU_STATUS |= SWAP32(PSXGPU_nBUSY);
 }
 
 static void SetBootRegs(u32 pc, u32 gp, u32 sp)
diff --git a/libpcsxcore/psxcounters.c b/libpcsxcore/psxcounters.c
index e19b7819..18bd6a4e 100644
--- a/libpcsxcore/psxcounters.c
+++ b/libpcsxcore/psxcounters.c
@@ -361,14 +361,20 @@ void psxRcntUpdate()
         // Update lace.
         if( hSyncCount >= HSyncTotal[Config.PsxType] )
         {
+            u32 status, field = 0;
             rcnts[3].cycleStart += Config.PsxType ? PSXCLK / 50 : PSXCLK / 60;
             hSyncCount = 0;
             frame_counter++;
 
             gpuSyncPluginSR();
-            if ((HW_GPU_STATUS & SWAP32(PSXGPU_ILACE_BITS)) == SWAP32(PSXGPU_ILACE_BITS))
-                HW_GPU_STATUS |= SWAP32(frame_counter << 31);
-            GPU_vBlank(0, SWAP32(HW_GPU_STATUS) >> 31);
+            status = SWAP32(HW_GPU_STATUS) | PSXGPU_FIELD;
+            if ((status & PSXGPU_ILACE_BITS) == PSXGPU_ILACE_BITS) {
+                field = frame_counter & 1;
+                status |= field << 31;
+                status ^= field << 13;
+            }
+            HW_GPU_STATUS = SWAP32(status);
+            GPU_vBlank(0, field);
         }
 
         scheduleRcntBase();
-- 
2.39.2