[PATCH v4 0/3] ECAP support on TI AM62x SoC

[Julien Panis]

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 (1->2->3->4->1->...), 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 CAP1/2/3/4 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...

Modifications since v3:
	- Migrate driver from IIO to Counter subsystem
	- Minor modification in yaml ($id) to match Counter subsystem
	- Add ABI documentation

Userspace commands :
	### SIGNAL ###
	cd /sys/bus/counter/devices/counter0/signal0

	# Get available polarities for each capture event
	cat polarity1_available
	cat polarity2_available
	cat polarity3_available
	cat polarity4_available

	# Get polarity for each capture event
	cat polarity1
	cat polarity2
	cat polarity3
	cat polarity4

	# Set polarity for each capture event
	echo rising > polarity1
	echo falling > polarity2
	echo rising > polarity3
	echo falling > polarity4

	### COUNT ###
	cd /sys/bus/counter/devices/counter0/count0

	# Run ECAP
	echo 1 > enable

	# Get current timebase counter value
	cat count

	# Get captured timestamps
	cat capture1
	cat capture2
	cat capture3
	cat capture4

	# Note that counter watches can also be used to get
	# data from userspace application
	# -> see tools/counter/counter_example.c

	# Stop ECAP
	echo 0 > enable

Julien Panis (3):
  dt-binding: counter: add ti,am62-ecap-capture.yaml
  Documentation: ABI: add sysfs-bus-counter-ecap
  counter: capture-tiecap: capture driver support for ECAP

 .../ABI/testing/sysfs-bus-counter-ecap        |  64 ++
 .../counter/ti,am62-ecap-capture.yaml         |  61 ++
 drivers/counter/Kconfig                       |  14 +
 drivers/counter/Makefile                      |   1 +
 drivers/counter/capture-tiecap.c              | 634 ++++++++++++++++++
 include/uapi/linux/counter.h                  |   2 +
 6 files changed, 776 insertions(+)
 create mode 100644 Documentation/ABI/testing/sysfs-bus-counter-ecap
 create mode 100644 Documentation/devicetree/bindings/counter/ti,am62-ecap-capture.yaml
 create mode 100644 drivers/counter/capture-tiecap.c

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