From: Julien Panis <jpanis@baylibre.com>
To: william.gray@linaro.org, robh+dt@kernel.org,
krzysztof.kozlowski+dt@linaro.org
Cc: linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org,
devicetree@vger.kernel.org, mranostay@ti.com
Subject: [PATCH v6 0/3] ECAP support on TI AM62x SoC
Date: Wed, 7 Sep 2022 15:03:24 +0200 [thread overview]
Message-ID: <20220907130327.139757-1-jpanis@baylibre.com> (raw)
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...
Modifications since v5:
- Fix descriptions for capture items in sysfs-bus-counter ABI file
- Modify TI_ECAP_CAPTURE help in Kconfig file
- Replace ecap_event_id enum with defines
- Add callbacks to reset nb_ovf & TSCNT
- Modify action_read callback to serve both clock and input signals
- Modify watch_validate callback
- Replace 'count_cumul' with 'num_overflows' & 'ceiling' components
- Replace one-based index with zero-based index for polarityX & captureX
- Reverse clock & input signal order (0/1)
- Move the check for overflow outside of the for-loop (in ISR)
- Push each CAPx event to respective counter event channels (in ISR)
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 available polarities for each capture event
cat polarity0_available
cat polarity1_available
cat polarity2_available
cat polarity3_available
# Get polarity for each capture event
cat polarity0
cat polarity1
cat polarity2
cat polarity3
# Set polarity for each capture event
echo rising edge > polarity0
echo falling edge > polarity1
echo rising edge > polarity2
echo falling edge > 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 (3):
dt-bindings: counter: add ti,am62-ecap-capture.yaml
Documentation: ABI: sysfs-bus-counter: add capture items
counter: ti-ecap-capture: capture driver support for ECAP
Documentation/ABI/testing/sysfs-bus-counter | 45 ++
.../counter/ti,am62-ecap-capture.yaml | 61 ++
drivers/counter/Kconfig | 15 +
drivers/counter/Makefile | 1 +
drivers/counter/ti-ecap-capture.c | 653 ++++++++++++++++++
include/uapi/linux/counter.h | 2 +
6 files changed, 777 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
next reply other threads:[~2022-09-07 13:03 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-07 13:03 Julien Panis [this message]
2022-09-07 13:03 ` [PATCH v6 1/3] dt-bindings: counter: add ti,am62-ecap-capture.yaml Julien Panis
2022-09-07 13:03 ` [PATCH v6 2/3] Documentation: ABI: sysfs-bus-counter: add capture items Julien Panis
2022-09-07 13:03 ` [PATCH v6 3/3] counter: ti-ecap-capture: capture driver support for ECAP Julien Panis
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