From 7886a60ef29cbeafffebf9867a0499e1b1330edd Mon Sep 17 00:00:00 2001
From: Zack Buhman <zack@buhman.org>
Date: Wed, 20 Aug 2025 21:56:42 -0500
Subject: [PATCH] add framebuffer, framebuffer_shaded, vo_border_col

---
 framebuffer.c        | 36 ++++++++++++++++++++++++++++++++++++
 framebuffer_shaded.c | 39 +++++++++++++++++++++++++++++++++++++++
 vo_border_col.c      | 18 ++++++++++++++++++
 3 files changed, 93 insertions(+)
 create mode 100644 framebuffer.c
 create mode 100644 framebuffer_shaded.c
 create mode 100644 vo_border_col.c

diff --git a/framebuffer.c b/framebuffer.c
new file mode 100644
index 0000000..f9aabc0
--- /dev/null
+++ b/framebuffer.c
@@ -0,0 +1,36 @@
+#include <stdint.h>
+
+void main()
+{
+  volatile uint32_t * texture_memory32 = (volatile uint32_t *)(0x05000000 | 0xA0000000);
+
+  int blue = 0x0000ff;
+  for (int i = 0; i < 640 * 480; i++) {
+    texture_memory32[i] = blue;
+  }
+
+  volatile uint32_t * FB_R_CTRL = (volatile uint32_t*)(0x005F8044 | 0xA0000000);
+
+  int vclk_div = 1;
+  int fb_depth = 0x3; // 0888 RGB 32 bit
+  int fb_enable = 1;
+  *FB_R_CTRL
+    = (vclk_div  << 23)
+    | (fb_depth  << 2 )
+    | (fb_enable << 0 );
+
+  volatile uint32_t * FB_R_SOF1 = (volatile uint32_t*)(0x005F8050 | 0xA0000000);
+  // the framebuffer is at the start of texture memory (texture memory address 0)
+  *FB_R_SOF1 = 0;
+
+  volatile uint32_t * FB_R_SIZE = (volatile uint32_t*)(0x005F805C | 0xA0000000);
+
+  int fb_modulus = 1;
+  int fb_y_size = 480 - 1;
+  int bytes_per_pixel = 4;
+  int fb_x_size = ((640 * bytes_per_pixel) / 4) - 1;
+  *FB_R_SIZE
+    = (fb_modulus << 20)
+    | (fb_y_size  << 10)
+    | (fb_x_size  << 0 );
+}
diff --git a/framebuffer_shaded.c b/framebuffer_shaded.c
new file mode 100644
index 0000000..29c02fc
--- /dev/null
+++ b/framebuffer_shaded.c
@@ -0,0 +1,39 @@
+#include <stdint.h>
+
+void main()
+{
+  volatile uint32_t * texture_memory32 = (volatile uint32_t *)(0x05000000 | 0xA0000000);
+
+  for (int y = 0; y < 480; y++) {
+    for (int x = 0; x < 640; x++) {
+      int red = (y % 255);
+      int blue = (x % 255);
+
+      texture_memory32[y * 640 + x] = (red << 16) | (blue << 0);
+    }
+  }
+
+  volatile uint32_t * FB_R_CTRL = (volatile uint32_t*)(0x005F8044 | 0xA0000000);
+  int vclk_div = 1;
+  int fb_depth = 0x3; // 0888 RGB 32 bit
+  int fb_enable = 1;
+  *FB_R_CTRL
+    = (vclk_div  << 23)
+    | (fb_depth  << 2 )
+    | (fb_enable << 0 );
+
+  volatile uint32_t * FB_R_SOF1 = (volatile uint32_t*)(0x005F8050 | 0xA0000000);
+  // the framebuffer is at the start of texture memory (texture memory address 0)
+  *FB_R_SOF1 = 0;
+
+  volatile uint32_t * FB_R_SIZE = (volatile uint32_t*)(0x005F805C | 0xA0000000);
+
+  int fb_modulus = 1;
+  int fb_y_size = 480 - 1;
+  int bytes_per_pixel = 4;
+  int fb_x_size = ((640 * bytes_per_pixel) / 4) - 1;
+  *FB_R_SIZE
+    = (fb_modulus << 20)
+    | (fb_y_size  << 10)
+    | (fb_x_size  << 0 );
+}
diff --git a/vo_border_col.c b/vo_border_col.c
new file mode 100644
index 0000000..2c2c293
--- /dev/null
+++ b/vo_border_col.c
@@ -0,0 +1,18 @@
+#include <stdint.h>
+
+typedef volatile uint32_t reg32;
+
+void main()
+{
+  reg32 * VO_BORDER_COL = (reg32 *)(0x005F8040 | 0xA0000000);
+  reg32 * FB_R_CTRL = (reg32 *)(0x005F8044 | 0xA0000000);
+
+  int vclk_div = 1;
+  int fb_enable = 0;
+  *FB_R_CTRL
+    = (vclk_div  << 23)
+    | (fb_enable <<  0);
+
+  int green = 0x00ff00;
+  *VO_BORDER_COL = green;
+}