From 0ab099077a160dad8815b6674ec28f4063305c82 Mon Sep 17 00:00:00 2001
From: Matt Harlum <matt@cactuar.net>
Date: Thu, 15 Jul 2021 15:21:14 +0200
Subject: [PATCH] slow-to-chip: Fixup agnus detection

Write to VPOSW before reading Agnus id seems to fix cold boot Agnus id read failure

Add "force-move-slow-to-chip" config option to force-disable Agnus check in case issue persists
---
 emulator.c                        |  1 +
 platforms/amiga/amiga-platform.c  | 12 ++++++++++--
 platforms/amiga/amiga-registers.h |  2 ++
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/emulator.c b/emulator.c
index fee4e5f..f71056c 100644
--- a/emulator.c
+++ b/emulator.c
@@ -45,6 +45,7 @@ int cpu_emulation_running = 1;
 int swap_df0_with_dfx = 0;
 int spoof_df0_id = 0;
 int move_slow_to_chip = 0;
+int force_move_slow_to_chip = 0;
 
 uint8_t mouse_dx = 0, mouse_dy = 0;
 uint8_t mouse_buttons = 0;
diff --git a/platforms/amiga/amiga-platform.c b/platforms/amiga/amiga-platform.c
index 5808d8a..3e64ed8 100644
--- a/platforms/amiga/amiga-platform.c
+++ b/platforms/amiga/amiga-platform.c
@@ -61,6 +61,7 @@ extern int mouse_hook_enabled;
 extern int swap_df0_with_dfx;
 extern int spoof_df0_id;
 extern int move_slow_to_chip;
+extern int force_move_slow_to_chip;
 
 #define min(a, b) (a < b) ? a : b
 #define max(a, b) (a > b) ? a : b
@@ -540,6 +541,11 @@ void setvar_amiga(struct emulator_config *cfg, char *var, char *val) {
         move_slow_to_chip = 1;
         printf("[AMIGA] Slow ram moved to Chip.\n");
     }
+
+    if CHKVAR("force-move-slow-to-chip") {
+        force_move_slow_to_chip = 1;
+        printf("[AMIGA] Forcing slowram move to chip, bypassing Agnus version check.\n");
+    }
 }
 
 void handle_reset_amiga(struct emulator_config *cfg) {
@@ -556,8 +562,9 @@ void handle_reset_amiga(struct emulator_config *cfg) {
     if (piscsi_enabled)
         piscsi_refresh_drives();
 
-    if (move_slow_to_chip) {
-      int agnus_rev = ((ps_read_16(0xDFF004) >> 8) & 0x6F);
+    if (move_slow_to_chip && !force_move_slow_to_chip) {
+      ps_write_16(VPOSW,0x00); // Poke poke... wake up Agnus!
+      int agnus_rev = ((ps_read_16(VPOSR) >> 8) & 0x6F);
       if (agnus_rev != 0x20) {
         move_slow_to_chip = 0;
         printf("[AMIGA] Requested move slow ram to chip but 8372 Agnus not found - Disabling.\n");
@@ -610,6 +617,7 @@ void shutdown_platform_amiga(struct emulator_config *cfg) {
     swap_df0_with_dfx = 0;
     spoof_df0_id = 0;
     move_slow_to_chip = 0;
+    force_move_slow_to_chip = 0;
 
     autoconfig_reset_all();
     printf("[AMIGA] Platform shutdown completed.\n");
diff --git a/platforms/amiga/amiga-registers.h b/platforms/amiga/amiga-registers.h
index c42a8f7..e41684f 100644
--- a/platforms/amiga/amiga-registers.h
+++ b/platforms/amiga/amiga-registers.h
@@ -43,6 +43,8 @@ void adjust_gayle_1200();
 #define POTGOR  0xDFF016
 #define SERDAT  0xDFF030
 
+#define VPOSR   0xDFF004
+#define VPOSW   0xDFF02A
 #define DMACON  0xDFF096
 #define DMACONR 0xDFF002