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
