Commit 0f4eeb63 authored Feb 08, 2025 by Andy Ross Committed by Benjamin Cabé Feb 13, 2025

soc/mediatek/mtk_adsp: Use smaller accesses when find()ing in device memory



Recent Python interpreters have started tossing bus errors from this
12-byte string search (the loader is looking for the winstream
descriptor in the live firmware image).  My guess is that there's a
SIMD optimization that's been added that's trying to do e.g. a 16 byte
load, and something in the fabric is kicking that out.  Note that this
is 100% a software change: the same hardware with one version of the
host environment works, and an update breaks it.

But really I have no idea what's happening here, the memory region in
question is documented as system DRAM, the same bus regular process
memory is on (it's just not kernel-utilized memory).  All I know is
that the bus error is introduced with a Python upgrade from 3.8.20 to
3.11.10.

Regardless, it's no great hardship to do the search on 64 bit chunks.

Signed-off-by: Andy Ross <andyross@google.com>

parent caafe238

soc/mediatek/mt8xxx/mtk_adsp_load.py

+7 −1

Original line number	Diff line number	Diff line
		@@ -277,7 +277,13 @@ def find_winstream(maps):
		magic = b'\x74\x5f\x6a\xd0\x79\xe2\x4f\x00\xcd\xb8\xbd\xf9'
		for m in maps:
		if "dram" in m:
		magoff = maps[m].find(magic)
		# Some python versions produce bus errors (!) on the
		# hardware when finding a 12 byte substring (maybe a SIMD
		# load that the hardware doesn't like?). Do it in two
		# chunks.
		magoff = maps[m].find(magic[0:8])
		if magoff >= 0:
		magoff = maps[m].find(magic[8:], magoff) - 8
		if magoff >= 0:
		addr = le4(maps[m][magoff + 12 : magoff + 16])
		return addr

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