From 6118f7080ddad100607a88a9ee96c18f65100822 Mon Sep 17 00:00:00 2001
From: OBattler <oubattler@gmail.com>
Date: Wed, 7 Aug 2024 17:34:09 +0200
Subject: [PATCH] Compaq EGA: Put the dot poll timer into the correct time
 after a timings recalculation, fixes POST errors on non-Compaq machines.

---
 src/video/vid_ega.c | 48 ++++++++++++++++++++++++++++++++++++---------
 1 file changed, 39 insertions(+), 9 deletions(-)

diff --git a/src/video/vid_ega.c b/src/video/vid_ega.c
index b05491bf0..a472f2e57 100644
--- a/src/video/vid_ega.c
+++ b/src/video/vid_ega.c
@@ -62,6 +62,7 @@ enum {
 
 static video_timings_t timing_ega = { .type = VIDEO_ISA, .write_b = 8, .write_w = 16, .write_l = 32, .read_b = 8, .read_w = 16, .read_l = 32 };
 static uint8_t         ega_rotate[8][256];
+static int             active             = 0;
 static uint32_t        pallook16[256];
 static uint32_t        pallook64[256];
 static int             ega_type           = EGA_TYPE_IBM;
@@ -155,6 +156,25 @@ ega_out(uint16_t addr, uint8_t val, void *priv)
             if (!(val & 1))
                 io_sethandler(0x03a0, 0x0020, ega_in, NULL, NULL, ega_out, NULL, NULL, ega);
             ega_recalctimings(ega);
+            if ((ega_type == 2) && !(val & 0x02))
+                mem_mapping_disable(&ega->mapping);
+            else  switch (ega->gdcreg[6] & 0xc) {
+                case 0x0: /*128k at A0000*/
+                    mem_mapping_set_addr(&ega->mapping, 0xa0000, 0x20000);
+                    break;
+                case 0x4: /*64k at A0000*/
+                    mem_mapping_set_addr(&ega->mapping, 0xa0000, 0x10000);
+                    break;
+                case 0x8: /*32k at B0000*/
+                    mem_mapping_set_addr(&ega->mapping, 0xb0000, 0x08000);
+                    break;
+                case 0xC: /*32k at B8000*/
+                    mem_mapping_set_addr(&ega->mapping, 0xb8000, 0x08000);
+                    break;
+
+                default:
+                    break;
+            }
             break;
         case 0x3c4:
             ega->seqaddr = val;
@@ -207,7 +227,9 @@ ega_out(uint16_t addr, uint8_t val, void *priv)
                     ega->chain2_read = val & 0x10;
                     break;
                 case 6:
-                    switch (val & 0xc) {
+                    if ((ega_type == 2) && !(ega->miscout & 0x02))
+                        mem_mapping_disable(&ega->mapping);
+                    else  switch (val & 0xc) {
                         case 0x0: /*128k at A0000*/
                             mem_mapping_set_addr(&ega->mapping, 0xa0000, 0x20000);
                             break;
@@ -593,9 +615,16 @@ ega_recalctimings(ega_t *ega)
     if (ega->dispofftime < TIMER_USEC)
         ega->dispofftime = TIMER_USEC;
 
-    ega->dot_time  = (uint64_t) (ega->dot_clock);
-    if (ega->dot_time < TIMER_USEC)
-        ega->dot_time = TIMER_USEC;
+    if (ega_type == 2) {
+        ega->dot_time  = (uint64_t) (ega->dot_clock);
+        if (ega->dot_time < TIMER_USEC)
+            ega->dot_time = TIMER_USEC;
+        timer_disable(&ega->dot_timer);
+        timer_set_delay_u64(&ega->dot_timer, ega->dot_time);
+        ega->cca = 0;
+        active = 1;
+        ega->dot = 0;
+    }
 
     ega_recalc_remap_func(ega);
 }
@@ -622,14 +651,13 @@ ega_dot_poll(void *priv)
     uint32_t addr;
     int drawcursor;
     uint32_t charaddr;
-    static int fg;
-    static int bg;
-    static uint32_t dat;
+    static int fg            = 0;
+    static int bg            = 0;
+    static uint32_t dat      = 0x00000000;
+    static int cclock        = 0;
     static int disptime;
     static int _dispontime;
     static int _dispofftime;
-    static int cclock = 0;
-    static int active = 0;
 
     if (ega->seqregs[1] & 8) {
         disptime    = ((ega->crtc[0] + 2) << 1);
@@ -1476,6 +1504,8 @@ ega_standalone_init(const device_t *info)
     ega->vrammask   = ega->vram_limit - 1;
 
     mem_mapping_add(&ega->mapping, 0xa0000, 0x20000, ega_read, NULL, NULL, ega_write, NULL, NULL, NULL, MEM_MAPPING_EXTERNAL, ega);
+    if (ega_type == 2)
+        mem_mapping_disable(&ega->mapping);
     io_sethandler(0x03c0, 0x0020, ega_in, NULL, NULL, ega_out, NULL, NULL, ega);
 
     if (ega->chipset) {