From af05a2979f97d00eab36261374af1eaf2ac3c833 Mon Sep 17 00:00:00 2001
From: Bad Diode <bd@badd10de.dev>
Date: Tue, 27 Apr 2021 12:36:28 +0200
Subject: Add DMA control macros and small memory copy test

---
 src/common.h | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 69 insertions(+)

(limited to 'src/common.h')

diff --git a/src/common.h b/src/common.h
index 669fb6e..e3405be 100644
--- a/src/common.h
+++ b/src/common.h
@@ -305,6 +305,7 @@ unpack_1bb(u8 hex) {
 }
 
 // Unpack N tiles packed at 1bpp.
+static inline void
 unpack_tiles(u32 *src, u32 *dst, size_t n_tiles) {
     u32 *target_src = src + n_tiles * 2;
     while (src != target_src) {
@@ -316,4 +317,72 @@ unpack_tiles(u32 *src, u32 *dst, size_t n_tiles) {
     }
 }
 
+//
+// Direct Memory Access (DMA)
+//
+
+
+// Source, destination, and control registers.
+#define DMA_SRC(N)  *((vu32*) 0x040000B0 + (N) * 12)
+#define DMA_DST(N)  *((vu32*) 0x040000B4 + (N) * 12)
+#define DMA_CTRL(N) *((vu32*) 0x040000B8 + (N) * 12)
+
+// DMA control bits.
+#define DMA_DST_INC    (0 << 0x15)
+#define DMA_DST_DEC    (1 << 0x15)
+#define DMA_DST_FIXED  (2 << 0x15)
+#define DMA_DST_RELOAD (3 << 0x15)
+#define DMA_SRC_INC    (0 << 0x17)
+#define DMA_SRC_DEC    (1 << 0x17)
+#define DMA_SRC_FIXED  (2 << 0x17)
+#define DMA_REPEAT     (1 << 0x19)
+#define DMA_CHUNK_16   (0 << 0x1A)
+#define DMA_CHUNK_32   (1 << 0x1A)
+#define DMA_NOW        (0 << 0x1C)
+#define DMA_VBLANK     (1 << 0x1C)
+#define DMA_HBLANK     (2 << 0x1C)
+#define DMA_REFRESH    (3 << 0x1C)
+#define DMA_IRQ        (1 << 0x1E)
+#define DMA_ENABLE     (1 << 0x1F)
+
+// Custom struct for cleaner DMA transfer functions.
+typedef struct DmaStr {
+    const void *src;
+    void *dst;
+    u32 ctrl;
+} DmaStr;
+
+#define DMA_TRANSFER ((volatile DmaStr*) 0x040000B0)
+
+// Transfer `count` number of chunks from src to dst using a DMA channel. Note
+// that chunks are not bytes, but instead configured based on bits set by
+// DMA_CTRL.
+inline void
+dma_transfer_copy(void *dst, const void *src, u32 count, int channel, u32 options) {
+    DMA_TRANSFER[channel].ctrl = 0;
+    DMA_TRANSFER[channel].src = src;
+    DMA_TRANSFER[channel].dst = dst;
+    DMA_TRANSFER[channel].ctrl = count | options;
+}
+
+inline void
+dma_transfer_fill(void *dst, volatile u32 src, u32 count, int channel, u32 options) {
+    DMA_TRANSFER[channel].ctrl = 0;
+    DMA_TRANSFER[channel].src = (const void *)&src;
+    DMA_TRANSFER[channel].dst = dst;
+    DMA_TRANSFER[channel].ctrl = count | options | DMA_SRC_FIXED;
+}
+
+// Copy N number of bytes using a DMA channel.
+inline void
+dma_copy(void *dst, const void *src, u32 size, int channel) {
+    dma_transfer_copy(dst, src, size / 4, channel, DMA_CHUNK_32 | DMA_ENABLE);
+}
+
+// Fill the dst location with the word set at src.
+inline void
+dma_fill(void *dst, const void *src, u32 size, int channel) {
+    dma_transfer_fill(dst, src, size / 4, channel, DMA_CHUNK_32 | DMA_ENABLE);
+}
+
 #endif // GBAEXP_COMMON_H
-- 
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