Skip to content

debugability: logger: add note on DMA trace limitations #381

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
lgirdwood merged 1 commit into from
Nov 15, 2021
Merged

debugability: logger: add note on DMA trace limitations #381

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
14 changes: 14 additions & 0 deletions developer_guides/debugability/logger/index.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -136,6 +136,20 @@ Examples
distribution kernels ``sof_debug=1`` module option for ``snd_sof`` might be
needed if the /sys/kernel/debug/sof/trace file is not present)

.. note::
If sof-logger is started (or restarted) while firmware is active, the initial
trace messages might be incomplete. This can happen as current (as of SOF version
1.9) trace is implemented with a ringbuffer between firmware and the kernel driver.
When sof-logger is started, kernel will always start to read the ringbuffer from
0 position, independently of firmware state. If firmware write pointer just wrapped
around when sof-logger is started, sof-logger will only show the traces after
the wrap. Firmware write position is also reset whenever firmware is booted,
including runtime suspend and resume. To capture traces over runtime suspend
events, the kernel trace interface will signal end of file at runtime suspend.
When sof-logger notices the end of file marker, it will reopen the trace
file and start reading from position 0 and thus be in sync with the firmware
when it is resumed.

Trace filtering
***************

Expand Down