The FPGA trace loop was the last OLD reply on the device outside the two
the bootrom also serves. It stayed OLD because the DMA double-buffer was
sized to the frame payload and an NG header did not obviously fit in
front of it.
DMA straight into chunk->data of a download_chunk_t instead, so a filled
buffer is already a complete NG payload and needs no copy. Chunking now
follows DOWNLOAD_CHUNK_MAX and scales with PM3_CMD_DATA_SIZE. The
terminator carries download_done_t like the other bulk downloads. No
client change needed, dl_it already had the NG branch.
Two fixes fall out of it:
FPGA_TRACE_SIZE is 3072, an exact multiple of 512 but not of
DOWNLOAD_CHUNK_MAX. Each transfer is now armed for exactly the bytes
still expected - arming a full chunk for the short last one would spin in
FPGA_SSC_DMA_RX_Done() forever. This also drops the stray extra DMA the
old loop left armed.
get_tosend() moved after FpgaDownloadAndGo(). The loader calls
BigBuf_free(), which nulls s_toSend.buf, then reuses that same region for
its decompression ring buffer - the old code captured the pointer before
the free and only worked because the loader was done with it in time.
3072 bytes goes from 6 OLD frames to 7 NG frames at PM3_CMD_DATA_SIZE
512, and would be 5 at 688.
iceman1001