From 443f6e1f2a8d83ad9da051cbb960311c5aaaea66 Mon Sep 17 00:00:00 2001
From: Joonas Javanainen <joonas.javanainen@gmail.com>
Date: Thu, 26 Sep 2024 20:16:51 +0300
Subject: [PATCH] Add timeouts to some LY waits

---
 common/common.s                   |  1 +
 common/lib/disable_ppu_safe.s     |  6 ++++-
 common/lib/quit.s                 | 14 ++++++++--
 common/lib/wait_ly_with_timeout.s | 45 +++++++++++++++++++++++++++++++
 utils/bootrom_dumper.s            |  1 +
 5 files changed, 64 insertions(+), 3 deletions(-)
 create mode 100644 common/lib/wait_ly_with_timeout.s

diff --git a/common/common.s b/common/common.s
index 9aab3bb..9b56c2b 100644
--- a/common/common.s
+++ b/common/common.s
@@ -103,6 +103,7 @@
 .include "lib/quit_dump_mem.s"
 .include "lib/reset_screen.s"
 .include "lib/serial_send_byte.s"
+.include "lib/wait_ly_with_timeout.s"
 
 ; --- Cartridge header ---
 
diff --git a/common/lib/disable_ppu_safe.s b/common/lib/disable_ppu_safe.s
index 6557ba9..153c2b8 100644
--- a/common/lib/disable_ppu_safe.s
+++ b/common/lib/disable_ppu_safe.s
@@ -30,7 +30,11 @@ disable_ppu_safe:
   ld hl, LCDC
   bit 7, (hl)
   ret z
-  wait_ly 144
+
+  push de
+  ld a, 144
+  call wait_ly_with_timeout
   res 7, (hl)
+  pop de
   ret
 .ends
diff --git a/common/lib/quit.s b/common/lib/quit.s
index ee656b0..1d5cf4f 100644
--- a/common/lib/quit.s
+++ b/common/lib/quit.s
@@ -46,15 +46,25 @@ quit:
     ret
 
   @cb_return:
+    push de
     call is_ppu_broken
     jr c, @report_result
 
     enable_ppu
-    wait_vblank
+
+    ld a, 143
+    call wait_ly_with_timeout
+    jr c, @report_result
+    ld a, 144
+    call wait_ly_with_timeout
     ; Extra vblank to account for initial (invisible) frame
-    wait_vblank
+    ld a, 143
+    call wait_ly_with_timeout
+    ld a, 144
+    call wait_ly_with_timeout
 
   @report_result:
+    pop de
     ld a, d
     and a
     jr nz, @failure
diff --git a/common/lib/wait_ly_with_timeout.s b/common/lib/wait_ly_with_timeout.s
new file mode 100644
index 0000000..ae26cb6
--- /dev/null
+++ b/common/lib/wait_ly_with_timeout.s
@@ -0,0 +1,45 @@
+; Copyright (C) 2014-2024 Joonas Javanainen <joonas.javanainen@gmail.com>
+;
+; Permission is hereby granted, free of charge, to any person obtaining a copy
+; of this software and associated documentation files (the "Software"), to deal
+; in the Software without restriction, including without limitation the rights
+; to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+; copies of the Software, and to permit persons to whom the Software is
+; furnished to do so, subject to the following conditions:
+;
+; The above copyright notice and this permission notice shall be included in
+; all copies or substantial portions of the Software.
+;
+; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+; IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+; FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+; AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+; LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+; OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+; SOFTWARE.
+
+.ifdef FORCE_SECTIONS
+.section "wait_ly_with_timeout" FORCE
+.else
+.section "wait_ly_with_timeout"
+.endif
+; Inputs:
+;   A expected LY value
+; Outputs:
+;   cf 0 if LY value was seen, 1 if the wait timed out
+; Preserved: E, HL
+wait_ly_with_timeout:
+  ld d, a
+  ld bc, $0000
+- ldh a, (<LY)
+  cp d
+  ret z ; cf=0 if the right LY value was seen
+  inc bc
+  ld a, b
+  or c
+  jr nz, -
+
+  @timeout:
+    scf
+    ret
+.ends
diff --git a/utils/bootrom_dumper.s b/utils/bootrom_dumper.s
index 15c44ca..794b42c 100644
--- a/utils/bootrom_dumper.s
+++ b/utils/bootrom_dumper.s
@@ -243,6 +243,7 @@ tilemap_sadface:
 .include "lib/reset_screen.s"
 .include "lib/serial_memcpy.s"
 .include "lib/serial_send_byte.s"
+.include "lib/wait_ly_with_timeout.s"
 
 .org $4000 - 3
   jp $7D00