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Force 4-byte alignment on the embedded firmware array #1

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Force 4-byte alignment on the embedded firmware array #1

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13 changes: 11 additions & 2 deletions target/atarist/firmware.py
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Original file line number Diff line number Diff line change
Expand Up @@ -32,8 +32,17 @@ def binary_to_c_array(input_source, output_file, array_name, endian_format="litt
if len(trimmed_data) % 2 != 0:
raise ValueError("The binary file size (after trimming zeros) should be an even number of bytes for word processing.")

# Prepare the output content
content = f"const uint16_t {array_name}[] = {{\n"
# Prepare the output content. The array MUST be 4-byte aligned: the
# RP2040 boot path copies it into ROM_IN_RAM with the XIP stream DMA
# (COPY_FIRMWARE_TO_RAM_DMA in memfunc.h), and the XIP STREAM_ADDR
# register silently truncates the source to a 32-bit word boundary.
# A uint16_t array is only 2-byte aligned, so a 2-mod-4 linker
# placement makes the stream start 2 bytes early -- the whole
# cartridge image lands in RAM shifted by 2 bytes and the m68k
# crashes (bombs / black screen / boot-to-desktop, varying per build
# because it depends purely on linker layout). aligned(4) makes the
# truncation a no-op.
content = f"const uint16_t __attribute__((aligned(4))) {array_name}[] = {{\n"

# Convert trimmed data to comma-separated hex values with MAX_WORDS_PER_LINE words per line
for i in range(offset, len(trimmed_data) - offset, 2 * MAX_WORDS_PER_LINE):
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