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From: Wolfram Sang <>
	Andy Shevchenko <>,
	Linus Walleij <>,
	Ulrich Hecht <>,
	Wolfram Sang <>
Subject: [RFC PATCH v2 0/1] gpio: add simple logic analyzer using polling
Date: Wed, 19 May 2021 15:25:27 +0200	[thread overview]
Message-ID: <> (raw)

The bravery continues with the second RFC for the in-kernel logic
analyzer based on GPIO polling with local irqs disabled. Besides the
driver, there is also a script which isolates a CPU to achieve the best
possible result. I am aware of the latency limitations. However, the
intention is only for debugging. Especially for remote debugging and to
get a first impression, this has already been useful. Documentation is
within the patch, to get a better idea what this is all about.

Changes since RFC v1:

* moved from misc/ to gpio/. Thanks to Linus and Bartosz for offering a
  home for this
* renamed from "simple logic analyzer" to "sloppy logic analyzer"
  everywhere to make its limitations crystal clear
* moved the parser for trigger data from the kernel into the script.
  Much cleaner kernel code but passing binary data now. We'll see...
* all gpios now must be named. This removes ugly fallback code and
  allows to use generic device properties instead of OF properties only.
* added and updated documentation
* triggers are also now checked at sample speed, not full speed
* replaced pr_* printouts with dev_*
* removed bashisms in the script (tested with bash, dash, and busybox
* depends on EXPERT now
* small bugfixes, refactoring, cleanups all around

Thanks to Andy, Linus, Randy, and Ulrich for suggestions and testing.

A branch with preparation for the Renesas Salvator-XS boards is here:
git:// renesas/gpio-logic-analyzer-v2

The documentation is also available online on the elinux wiki:

Looking forward to comments and especially further tests with different
use cases than mine. I have looked enough at the code, fresh view would
really help. And still, if somebody has a pointer how to detect if a
task was requested to be killed (while irqs and preemption are
disabled), I'd appreciate that to avoid the currently unkillable

All the best,


Wolfram Sang (1):
  misc: add sloppy logic analyzer using polling

 .../dev-tools/gpio-sloppy-logic-analyzer.rst  |  72 ++++
 Documentation/dev-tools/index.rst             |   1 +
 drivers/gpio/Kconfig                          |  17 +
 drivers/gpio/Makefile                         |   1 +
 drivers/gpio/gpio-sloppy-logic-analyzer.c     | 317 ++++++++++++++++++
 tools/gpio/gpio-sloppy-logic-analyzer         | 200 +++++++++++
 6 files changed, 608 insertions(+)
 create mode 100644 Documentation/dev-tools/gpio-sloppy-logic-analyzer.rst
 create mode 100644 drivers/gpio/gpio-sloppy-logic-analyzer.c
 create mode 100755 tools/gpio/gpio-sloppy-logic-analyzer


             reply	other threads:[~2021-05-19 13:26 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-19 13:25 Wolfram Sang [this message]
2021-05-19 13:25 ` [RFC PATCH v2 1/1] misc: add sloppy " Wolfram Sang
2021-05-19 14:49   ` Andy Shevchenko
2021-07-30 19:57     ` Wolfram Sang
2021-07-30 20:45       ` Andy Shevchenko
2021-08-10  8:32         ` Wolfram Sang
2021-08-11 12:40           ` Andy Shevchenko

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