From ed30b2cb21c429620323a448b49d287b96eb7f3f Mon Sep 17 00:00:00 2001
From: Lephe <sebastien.michelland@protonmail.com>
Date: Thu, 2 Jul 2020 15:47:11 +0200
Subject: [PATCH] render-cg: allow VRAM in user stack

This is currently unused and has some artifacts in gintctl for reasons I
haven't understood yet. Will have to investigate later.
---
 configure             |  8 +++++---
 fxcg50.ld             | 15 +++++----------
 src/render-cg/dvram.c | 24 +++++++++++++++++++++---
 3 files changed, 31 insertions(+), 16 deletions(-)

diff --git a/configure b/configure
index e800ebb..d7d8b32 100755
--- a/configure
+++ b/configure
@@ -13,9 +13,9 @@ prefix=
 cflags=
 
 # Behavior
-boot_log=
 no_syscalls=
 static_gray=
+user_vram=
 
 # Size limits
 atexit_max=
@@ -57,6 +57,7 @@ Library options (disabled by default):
                        Only use this option if you have a good idea of which.
   --static-gray        Allocate gray VRAMs in static RAM instead of the heap
                        May help when --no-syscalls is on.
+  --user-vram          Allocate VRAM in user stack; takes 350k/512k [fxcg50]
 
 Size limits:
   --atexit-max=NUM     Number of exit handlers in atexit()'s array [16]
@@ -109,12 +110,12 @@ for arg; do case "$arg" in
   --cflags=*)
     cflags=${arg#*=};;
 
-  --boot-log)
-    boot_log=true;;
   --no-syscalls)
     no_syscalls=true;;
   --static-gray)
     static_gray=true;;
+  --user-vram)
+    user_vram=true;;
 
   --atexit-max=*)
     n=${arg#*=}
@@ -190,6 +191,7 @@ output_config()
   echo -n " -D$(echo $target | tr 'a-z' 'A-Z')"
   [[ "$no_syscalls" ]] && echo -n " -DGINT_NO_SYSCALLS"
   [[ "$static_gray" ]] && echo -n " -DGINT_STATIC_GRAY"
+  [[ "$user_vram"   ]] && echo -n " -DGINT_USER_VRAM"
   [[ "$atexit_max"  ]] && echo -n " -DATEXIT_MAX=$atexit_max"
   echo ""
 }
diff --git a/fxcg50.ld b/fxcg50.ld
index 505f2f6..8a4f2b6 100644
--- a/fxcg50.ld
+++ b/fxcg50.ld
@@ -68,18 +68,14 @@ SECTIONS
 		*(.text .text.*)
 	} > rom
 
-	/* Interrupt handlers going to ROM:
-	   - gint's interrupt handler blocks (.gint.blocks)
-
-	   Although gint's blocks end up in VBR space, they are installed at
+	/* gint's interrupt handler blocks (.gint.blocks)
+	   Although gint's blocks end up in VBR space, they are relocated at
 	   startup by the library/drivers, so we store them here for now */
 	.gint.blocks : {
 		KEEP(*(.gint.blocks));
 	} > rom
 
-	/* Driver data going to ROM:
-	   - Exposed driver interfaces (.gint.drivers)
-
+	/* Exposed driver interfaces (.gint.drivers)
 	   The driver information is required to start and configure the
 	   driver, even if the symbols are not referenced */
 	.gint.drivers : {
@@ -117,6 +113,7 @@ SECTIONS
 	.bss (NOLOAD) : {
 		_rbss = . ;
 
+		*(.bss.vram)
 		*(.bss COMMON)
 
 		. = ALIGN(16);
@@ -183,9 +180,7 @@ SECTIONS
 
 
 	/*
-	**  gint-related sections
-	**  8c160000:5k  VBR space
-	**  8c161400:3k  .gint.data and .gint.bss
+	**  gint-related sections (VBR space, .gint.data and .gint.bss)
 	*/
 
 	/* VBR address: let's just start at the beginning of the RAM area.
diff --git a/src/render-cg/dvram.c b/src/render-cg/dvram.c
index 392475f..d7f4584 100644
--- a/src/render-cg/dvram.c
+++ b/src/render-cg/dvram.c
@@ -1,13 +1,31 @@
 #include <gint/display.h>
 
-/* Put both VRAMs in the system stack! */
+#ifdef GINT_USER_VRAM
+/* We want to put the VRAM in the user section, however we can't use the
+   virtualized P0 address as this will mess up the DMA. As the static RAM is
+   always fully mapped at a fixed place, we can use the target P1 address. We
+   just need to allocate the space for the linker. This special section ensures
+   that the first address of the user stack will be used */
+GALIGNED(4) GSECTION(".bss.vram") int8_t _gint_vram_buffers[396*224*2];
+
+/* In this case, we can define pointers to our user stack directly, these will
+   be the physical address associated with _vram_buffers */
+static uint16_t *main = (void *)0xac161400;
+static uint16_t *scnd = (void *)0xac18c900;
+
+/* Shared VRAM pointer, the one exposed by <gint/display.h> */
+uint16_t *gint_vram = (void *)0xac161400;
+
+#else
+
+/* Otherwise, just put both VRAMs in the system stack! */
 static uint16_t *main = (void *)0xac0f0000;
 static uint16_t *scnd = (void *)0xac11b500;
+uint16_t *gint_vram = (void *)0xac0f0000;
+#endif
 
 /* On Prizm: should be: 0xa80f0000 and 0xa811b500 */
 
-/* Shared VRAM pointer, the one exposed by <gint/display.h> */
-uint16_t *gint_vram = (void *)0xac0f0000;
 
 /* dsetvram() - Control video RAM address and triple buffering */
 void dsetvram(uint16_t *new_main, uint16_t *new_secondary)