linux-kernel - Re: [PATCH v9 0/4] ECAP support on TI AM62x SoC

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Date:   Tue, 27 Sep 2022 17:49:09 -0400
From:   William Breathitt Gray <wbg@...nel.org>
To:     Julien Panis <jpanis@...libre.com>
Cc:     william.gray@...aro.org, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        mranostay@...com
Subject: Re: [PATCH v9 0/4] ECAP support on TI AM62x SoC

On Fri, Sep 23, 2022 at 04:24:33PM +0200, Julien Panis wrote:
> The Enhanced Capture (ECAP) module can be used to timestamp events
> detected on signal input pin. It can be used for time measurements
> of pulse train signals.
> 
> ECAP module includes 4 timestamp capture registers. For all 4 sequenced
> timestamp capture events (0->1->2->3->0->...), edge polarity (falling/rising
> edge) can be selected.
> 
> This driver leverages counter subsystem to :
> - select edge polarity for all 4 capture events (event mode)
> - log timestamps for each capture event
> Event polarity, and CAP0/1/2/3 timestamps give all the information
> about the input pulse train. Further information can easily be computed :
> period and/or duty cycle if frequency is constant, elapsed time between
> pulses, etc...
> 
> This patchset must be applied on top of the following counter subsystem patchset :
> https://lore.kernel.org/all/cover.1663693757.git.william.gray@linaro.org/
> 
> Modifications since v8 :
> 	- Add documentation to private driver structure
> 	- Add mutex to prevent IO race conditions
> 	- Stop counter before disabling interrupts in ecap_cnt_capture_disable() function
> 	- Remove returning of status in ecap_cnt_count_get/set_val() functions
> 	- Remove unnecessary 'return -EBUSY' in all callbacks
> 	- Remove unnecessary '.id = 0' in ecap_cnt_counts[]
> 	- Modify driver info in MAINTAINER file
> 
> Userspace commands :
> 	### CLOCK SIGNAL ###
> 	cd /sys/bus/counter/devices/counter0/signal0
> 
> 	# Get frequency
> 	cat frequency
> 
> 	### INPUT SIGNAL ###
> 	cd /sys/bus/counter/devices/counter0/signal1
> 
> 	# Get polarity for each capture event
> 	cat polarity0
> 	cat polarity1
> 	cat polarity2
> 	cat polarity3
> 
> 	# Set polarity for each capture event
> 	echo positive > polarity0
> 	echo negative > polarity1
> 	echo positive > polarity2
> 	echo negative > polarity3
> 
> 	### COUNT ###
> 	cd /sys/bus/counter/devices/counter0/count0
> 
> 	# Get ceiling (counter max value)
> 	cat ceiling
> 
> 	# Reset number of overflows & current timebase counter value
> 	echo 0 > num_overflows
> 	echo 0 > count
> 
> 	# Run ECAP
> 	echo 1 > enable
> 
> 	# Get number of overflows & current timebase counter value
> 	cat num_overflows
> 	cat count
> 
> 	# Get captured timestamps
> 	cat capture0
> 	cat capture1
> 	cat capture2
> 	cat capture3
> 
> 	# Note that counter watches can also be used to get
> 	# data from userspace application
> 	# -> see tools/counter/counter_example.c
> 
> 	# Pause ECAP
> 	echo 0 > enable
> 
> Julien Panis (4):
>   dt-bindings: counter: add ti,am62-ecap-capture.yaml
>   Documentation: ABI: sysfs-bus-counter: add frequency & num_overflows
>     items
>   counter: ti-ecap-capture: capture driver support for ECAP
>   MAINTAINERS: add TI ECAP driver info
> 
>  Documentation/ABI/testing/sysfs-bus-counter   |  14 +
>  .../counter/ti,am62-ecap-capture.yaml         |  61 ++
>  MAINTAINERS                                   |   9 +
>  drivers/counter/Kconfig                       |  15 +
>  drivers/counter/Makefile                      |   1 +
>  drivers/counter/ti-ecap-capture.c             | 614 ++++++++++++++++++
>  6 files changed, 714 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/counter/ti,am62-ecap-capture.yaml
>  create mode 100644 drivers/counter/ti-ecap-capture.c
> 
> -- 
> 2.37.3

Queued for counter-next with a minor context adjustment for
sysfs-bus-counter changes.

Thanks,

William Breathitt Gray

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