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

--
2.25.1

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