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Drop copy_to_ram. It was always the lazy option - I didn't want to work out which functions actually needed to be in SRAM, so I put all of them there. Now that the audio core is marked, the linker script already does the right thing: it pulls '.time_critical*' out of flash, and everything else is cold enough to run from XIP. RAM before: 73132 text + 386972 bss = 460104 RAM after: 20504 data + 384652 bss = 405156 which is 54948 bytes back, and takes the headroom from 70K to 124K out of 520K. That matters more than it sounds: bss is already 384K, mostly the 64K analyzer ring and the 64K FFT buffer, so headroom is the thing that was going to run out first. Also add scripts/check-audio.py, run after every link. Everything in a '.time_critical.audio_*' section may only call into another one, and anything else fails the build. Right now there is nothing on the allowed list at all - the audio path doesn't call a single library function - which is the whole reason to add the check now rather than after it has rotted. The last one to go was the newlib 'lrintf()' a couple of commits ago. The one thing this cannot check is that the code still *works* from flash. cpu1 is unaffected by construction since all of it is in RAM, but cpu0 now takes XIP cache misses, and the tuner does an 8192-point FFT at 25Hz. I think the cache holds the inner loop fine. I have not proven it on hardware. Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
79 lines
2.7 KiB
Python
Executable File
79 lines
2.7 KiB
Python
Executable File
#!/usr/bin/env python3
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#
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# Check that nothing running on the audio core calls out of it.
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#
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# Everything marked with __audio_func() is compiled into its own
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# '.time_critical.audio_<name>' section. Anything such a function calls
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# has to be marked too - if it isn't, either it wants marking, or we have
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# accidentally pulled a newlib or soft-float routine into the
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# hard-realtime path.
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#
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# The linker merges all of those input sections into .data, so the
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# section names only survive in the map file. That is fine: the macro
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# builds the section name out of the function name, so the map is enough
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# to recover the list.
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#
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# Called as: check-audio.py <map> <elf> [objdump]
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#
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import re
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import subprocess
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import sys
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# Calls allowed out of the audio sections. Keep this short, and say why.
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ALLOWED = {
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# (nothing yet - the audio path is entirely self-contained)
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}
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def main():
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mapfile, elf = sys.argv[1], sys.argv[2]
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objdump = (sys.argv[3] if len(sys.argv) > 3 and sys.argv[3]
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else "arm-none-eabi-objdump")
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with open(mapfile) as f:
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audio = set(re.findall(r"^ \.time_critical\.audio_(\S+)$",
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f.read(), re.M))
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if not audio:
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sys.exit("check-audio: no __audio_func() symbols in the map - "
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"stale build?")
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res = subprocess.run([objdump, "-d", "--no-show-raw-insn", elf],
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capture_output=True, text=True)
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if res.returncode:
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sys.exit(f"check-audio: {objdump} failed:\n{res.stderr}")
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func = re.compile(r"^[0-9a-f]+ <([^>]+)>:")
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call = re.compile(r"\s(?:bl|blx)\s+[0-9a-f]+ <([^>+]+)")
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cur, bad, seen = None, set(), set()
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for line in res.stdout.splitlines():
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m = func.match(line)
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if m:
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cur = m.group(1)
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if cur in audio:
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seen.add(cur)
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continue
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m = call.search(line)
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if m and cur in audio:
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callee = m.group(1)
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if callee not in audio and callee not in ALLOWED:
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bad.add((cur, callee))
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# A marked function that vanished was fully inlined into its callers,
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# which is fine - they are marked too.
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if bad:
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print(f"check-audio: {len(bad)} call(s) leaving the audio core:",
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file=sys.stderr)
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for caller, callee in sorted(bad):
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print(f" {caller} -> {callee}", file=sys.stderr)
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print("\nMark the callee with __audio_func(), or if it really has to "
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"live\nout of line, add it to ALLOWED in this script with a "
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"reason.", file=sys.stderr)
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return 1
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print(f"check-audio: {len(seen)} functions on the audio core, no calls out")
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return 0
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if __name__ == "__main__":
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sys.exit(main())
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