[PATCH v8 0/4] ECAP support on TI AM62x SoC

From: Julien Panis
Date: Thu Sep 22 2022 - 13:04:18 EST


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@xxxxxxxxxx/

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

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2.37.3