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Subject[PATCH v8 0/4] 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 (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 v7 :
- Simplify ecap_cnt_capture_get/set_evmode() functions
- Modify ecap_cnt_count_write() callback
- Modify ecap_cnt_watch_validate() callback
- Modify ecap_cnt_pol_read() callback
- Add ecap_cnt_cap_write() callback
- Modify ecap_cnt_nb_ovf_write() callback
- Use DEFINE_COUNTER_ARRAY_CAPTURE() and COUNTER_COMP_ARRAY_CAPTURE() macros
- Push COUNTER_EVENT_OVERFLOW to all 4 channels in ISR
- Redefine time_cntr and related functions as u32
- Remove ecap_cnt_capture_set_evmode() function call in probe function

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 | 7 +
drivers/counter/Kconfig | 15 +
drivers/counter/Makefile | 1 +
drivers/counter/ti-ecap-capture.c | 621 ++++++++++++++++++
6 files changed, 719 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

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