From cd0636ee0434b8f6068b5962f825d5f79777e694 Mon Sep 17 00:00:00 2001
From: OBattler <oubattler@gmail.com>
Date: Thu, 11 Jan 2024 14:42:54 +0100
Subject: [PATCH] Fixed horizontal retrace start and end extensions on almost
 every applicable card, fixes #4025.

---
 src/video/vid_et4000.c         |  4 +-
 src/video/vid_et4000w32.c      |  4 +-
 src/video/vid_mga.c            |  9 +++--
 src/video/vid_s3.c             | 18 ++++-----
 src/video/vid_s3_virge.c       | 12 +++---
 src/video/vid_voodoo_banshee.c | 68 +++++++++++++++++-----------------
 6 files changed, 56 insertions(+), 59 deletions(-)

diff --git a/src/video/vid_et4000.c b/src/video/vid_et4000.c
index 882a3e12e..1b868ecd7 100644
--- a/src/video/vid_et4000.c
+++ b/src/video/vid_et4000.c
@@ -613,11 +613,11 @@ et4000_recalctimings(svga_t *svga)
         svga->rowoffset = 0x100;
     if (svga->crtc[0x3f] & 1)
         svga->htotal += 256;
-    if (svga->crtc[0x3f] & 0x04)
-        svga->hblankstart += 0x100;
     if (svga->attrregs[0x16] & 0x20)
         svga->hdisp <<= 1;
 
+    svga->hblankstart    = (((svga->crtc[0x3f] & 0x10) >> 4) << 8) + svga->crtc[4] + 1;
+
     switch (((svga->miscout >> 2) & 3) | ((svga->crtc[0x34] << 1) & 4)) {
         case 0:
         case 1:
diff --git a/src/video/vid_et4000w32.c b/src/video/vid_et4000w32.c
index 0133b728b..3ba134342 100644
--- a/src/video/vid_et4000w32.c
+++ b/src/video/vid_et4000w32.c
@@ -445,11 +445,11 @@ et4000w32p_recalctimings(svga_t *svga)
         svga->rowoffset += 0x100;
     if (svga->crtc[0x3F] & 0x01)
         svga->htotal += 256;
-    if (svga->crtc[0x3F] & 0x04)
-        svga->hblankstart += 0x100;
     if (svga->attrregs[0x16] & 0x20)
         svga->hdisp <<= 1;
 
+    svga->hblankstart    = (((svga->crtc[0x3f] & 0x10) >> 4) << 8) + svga->crtc[4] + 1;
+
     svga->clock = (cpuclock * (double) (1ULL << 32)) / svga->getclock((svga->miscout >> 2) & 3, svga->clock_gen);
 
     if (et4000->type != ET4000W32P_DIAMOND) {
diff --git a/src/video/vid_mga.c b/src/video/vid_mga.c
index 9fa9e9389..d386bdb71 100644
--- a/src/video/vid_mga.c
+++ b/src/video/vid_mga.c
@@ -943,8 +943,9 @@ mystique_recalctimings(svga_t *svga)
 
     if (mystique->crtcext_regs[1] & CRTCX_R1_HTOTAL8)
         svga->htotal |= 0x100;
-    if (mystique->crtcext_regs[1] & CRTCX_R1_HBLKSTRT8)
-        svga->hblankstart += 0x100;
+
+    svga->hblankstart    = (((mystique->crtcext_regs[1] & 0x04) >> 2) << 8) + svga->crtc[4] + 1;
+
     if (mystique->crtcext_regs[2] & CRTCX_R2_VTOTAL10)
         svga->vtotal |= 0x400;
     if (mystique->crtcext_regs[2] & CRTCX_R2_VTOTAL11)
@@ -975,8 +976,8 @@ mystique_recalctimings(svga_t *svga)
         svga->hdisp_time    = svga->hdisp;
         svga->rowoffset     = svga->crtc[0x13] | ((mystique->crtcext_regs[0] & CRTCX_R0_OFFSET_MASK) << 4);
 
-        svga->hblank_end_len = 0x80;
-        svga->hblank_end_val += mystique->crtcext_regs[1] & CRTCX_R1_HBLKEND6;
+        svga->hblank_end_val = (mystique->crtcext_regs[1] & 0x40) | (svga->crtc[3] & 0x1f) |
+                               ((svga->crtc[5] & 0x80) ? 0x20 : 0x00);
 
         svga->hblank_overscan = 0;
 
diff --git a/src/video/vid_s3.c b/src/video/vid_s3.c
index 6f648f628..073b8523f 100644
--- a/src/video/vid_s3.c
+++ b/src/video/vid_s3.c
@@ -3988,6 +3988,8 @@ s3_recalctimings(svga_t *svga)
             svga->dots_per_clock = ((svga->seqregs[1] & 1) ? 16 : 18);
         }
 
+        svga->hblankstart    = (((svga->crtc[0x5d] & 0x10) >> 4) << 8) + svga->crtc[4] + 1;
+
         if (svga->crtc[0x5d] & 0x04)
             svga->hblankstart += 0x100;
         if (s3->chip >= S3_VISION964) {
@@ -3995,12 +3997,8 @@ s3_recalctimings(svga_t *svga)
                      The datasheets for the pre-Trio64V+ cards say +64, which implies bit 6,
                      and, contrary to VGADOC, it also exists on Trio32, Trio64, Vision868,
                      and Vision968. */
-#if 0
-            pclog("svga->crtc[0x5d] = %02X\n", svga->crtc[0x5d]);
-#endif
-            if (svga->crtc[0x5d] & 0x08)
-                svga->hblank_ext = 0x40;
-            svga->hblank_end_len = 0x00000040;
+            svga->hblank_end_val = (svga->crtc[3] & 0x1f) | (((svga->crtc[5] & 0x80) >> 7) << 5) |
+                                   (((svga->crtc[0x5d] & 0x08) >> 3) << 6);
         }
     }
 
@@ -4152,16 +4150,14 @@ s3_trio64v_recalctimings(svga_t *svga)
         }
     }
 
-    if (svga->crtc[0x5d] & 0x04)
-        svga->hblankstart += 0x100;
+    svga->hblankstart    = (((svga->crtc[0x5d] & 0x10) >> 4) << 8) + svga->crtc[4] + 1;
 
     /* NOTE: The S3 Trio64V+ datasheet says this is bit 7, but then where is bit 6?
              The datasheets for the pre-Trio64V+ cards say +64, which implies bit 6,
              and, contrary to VGADOC, it also exists on Trio32, Trio64, Vision868,
              and Vision968. */
-    if (svga->crtc[0x5d] & 0x08)
-        svga->hblank_ext = 0x40;
-    svga->hblank_end_len = 0x00000040;
+    svga->hblank_end_val = (svga->crtc[3] & 0x1f) | (((svga->crtc[5] & 0x80) >> 7) << 5) |
+                           (((svga->crtc[0x5d] & 0x08) >> 3) << 6);
 
     svga->hblank_overscan = !(svga->crtc[0x33] & 0x20);
 }
diff --git a/src/video/vid_s3_virge.c b/src/video/vid_s3_virge.c
index 76195189f..f398aa80b 100644
--- a/src/video/vid_s3_virge.c
+++ b/src/video/vid_s3_virge.c
@@ -911,13 +911,11 @@ s3_virge_recalctimings(svga_t *svga)
         }
         svga->vram_display_mask = virge->vram_mask;
     }
-    
-    if (svga->crtc[0x5d] & 0x04)
-        svga->hblankstart += 0x100;
-    
-    if (svga->crtc[0x5d] & 0x08)
-        svga->hblank_ext = 0x40;
-    svga->hblank_end_len = 0x00000040;
+
+    svga->hblankstart    = (((svga->crtc[0x5d] & 0x10) >> 4) << 8) + svga->crtc[4] + 1;
+
+    svga->hblank_end_val = (svga->crtc[3] & 0x1f) | (((svga->crtc[5] & 0x80) >> 7) << 5) |
+                           (((svga->crtc[0x5d] & 0x08) >> 3) << 6);
 
     svga->hblank_overscan = !(svga->crtc[0x33] & 0x20);
 }
diff --git a/src/video/vid_voodoo_banshee.c b/src/video/vid_voodoo_banshee.c
index e10337928..31e0d34d4 100644
--- a/src/video/vid_voodoo_banshee.c
+++ b/src/video/vid_voodoo_banshee.c
@@ -540,37 +540,40 @@ banshee_recalctimings(svga_t *svga)
     banshee_t      *banshee = (banshee_t *) svga->priv;
     const voodoo_t *voodoo  = banshee->voodoo;
 
-    /*7 R/W Horizontal Retrace End bit 5. -
-      6 R/W Horizontal Retrace Start bit 8 0x4
-      5 R/W Horizontal Blank End bit 6. -
-      4 R/W Horizontal Blank Start bit 8. 0x3
-      3 R/W Reserved. -
-      2 R/W Horizontal Display Enable End bit 8. 0x1
-      1 R/W Reserved. -
-      0 R/W Horizontal Total bit 8. 0x0*/
-    if (svga->crtc[0x1a] & 0x01)
-        svga->htotal += 0x100;
-    if (svga->crtc[0x1a] & 0x04)
-        svga->hdisp += 0x100;
-    if (svga->crtc[0x1a] & 0x10)
-        svga->hblankstart += 0x100;
-    if (svga->crtc[0x1a] & 0x20)
-        svga->hblank_end_val += 0x40;
-    /*6 R/W Vertical Retrace Start bit 10 0x10
-      5 R/W Reserved. -
-      4 R/W Vertical Blank Start bit 10. 0x15
-      3 R/W Reserved. -
-      2 R/W Vertical Display Enable End bit 10 0x12
-      1 R/W Reserved. -
-      0 R/W Vertical Total bit 10. 0x6*/
-    if (svga->crtc[0x1b] & 0x01)
-        svga->vtotal += 0x400;
-    if (svga->crtc[0x1b] & 0x04)
-        svga->dispend += 0x400;
-    if (svga->crtc[0x1b] & 0x10)
-        svga->vblankstart += 0x400;
-    if (svga->crtc[0x1b] & 0x40)
-        svga->vsyncstart += 0x400;
+    if (banshee->vgaInit0 & 0x40) {
+        /*7 R/W Horizontal Retrace End bit 5. -
+          6 R/W Horizontal Retrace Start bit 8 0x4
+          5 R/W Horizontal Blank End bit 6. -
+          4 R/W Horizontal Blank Start bit 8. 0x3 ---- Erratum: Actually, 0x02!
+          3 R/W Reserved. -
+          2 R/W Horizontal Display Enable End bit 8. 0x1
+          1 R/W Reserved. -
+          0 R/W Horizontal Total bit 8. 0x0*/
+        if (svga->crtc[0x1a] & 0x01)
+            svga->htotal += 0x100;
+        if (svga->crtc[0x1a] & 0x04)
+            svga->hdisp += 0x100;
+
+        svga->hblankstart    = (((svga->crtc[0x1a] & 0x40) >> 6) << 8) + svga->crtc[4] + 1;
+        svga->hblank_end_val = (svga->crtc[3] & 0x1f) | (((svga->crtc[5] & 0x80) >> 7) << 5) |
+                               (((svga->crtc[0x1a] & 0x20) >> 5) << 6);
+
+        /*6 R/W Vertical Retrace Start bit 10 0x10
+          5 R/W Reserved. -
+          4 R/W Vertical Blank Start bit 10. 0x15
+          3 R/W Reserved. -
+          2 R/W Vertical Display Enable End bit 10 0x12
+          1 R/W Reserved. -
+          0 R/W Vertical Total bit 10. 0x6*/
+        if (svga->crtc[0x1b] & 0x01)
+            svga->vtotal += 0x400;
+        if (svga->crtc[0x1b] & 0x04)
+            svga->dispend += 0x400;
+        if (svga->crtc[0x1b] & 0x10)
+            svga->vblankstart += 0x400;
+        if (svga->crtc[0x1b] & 0x40)
+            svga->vsyncstart += 0x400;
+    }
 #if 0
     banshee_log("svga->hdisp=%i\n", svga->hdisp);
 #endif
@@ -615,8 +618,6 @@ banshee_recalctimings(svga_t *svga)
         svga->char_width = 8;
         svga->split      = 99999;
 
-        svga->hblank_end_len = 0x80;
-
         if (banshee->vidProcCfg & VIDPROCCFG_2X_MODE) {
             svga->hdisp *= 2;
             svga->htotal *= 2;
@@ -801,6 +802,7 @@ banshee_ext_outl(uint16_t addr, uint32_t val, void *priv)
         case Init_vgaInit0:
             banshee->vgaInit0 = val;
             svga_set_ramdac_type(svga, (val & VGAINIT0_RAMDAC_8BIT ? RAMDAC_8BIT : RAMDAC_6BIT));
+            svga_recalctimings(svga);
             break;
         case Init_vgaInit1:
             banshee->vgaInit1   = val;