[PATCH v4 0/3] Add the System Timer Module counter

[Daniel Lezcano <daniel.lezcano@linaro.org>]

The NXP S32 family provides a System Timer Module (STM), a 32-bit
free-running counter clocked from a peripheral clock. The STM includes
a prescaler and one or more compare channels generating optional
interrupts. When used as a generic hardware counter, only the main
free-running counter is required, while the compare channels are
typically unused.

On S32G2 devices, the STM is exposed as a simple counter block that
can operate continuously and be shared across subsystems such as the
Linux kernel, firmware components running on Cortex-M7 cores, or other
co-processors. The counter can be read atomically and provides a
stable timestamp source to correlate events occurring in different
execution contexts.

The Linux kernel controls the STM through a memory-mapped interface,
configuring the prescaler, enabling or disabling the counter, and
accounting for wrap-arounds. Other subsystems access the counter in
read-only mode, making it a shared timestamp reference across the
platform.

This driver adds support for the STM when used as a counter on S32G2
platforms. The device is described in the device tree using the
following compatible:

compatible = "nxp,s32g2-stm-cnt";

The driver exposes basic counter functionality: start, stop, reset,
prescaler configuration, and overflow handling.

Changelog:
	* v4
	  - Split context structure to suspend/resume
	  - Converted counter to a u64 to accumulate the time
	  - Replaced 'reset' to a count write to reset (William Breathitt Gray)
	  - Added events for userspace (William Breathitt Gray)
	  - Added action COUNTER_SYNAPSE_ACTION_RISING_EDGE for signal (William Breathitt Gray)
	  - Renamed counter name to "System Timer Module Counter" (William Breathitt Gray)

	* v3
	  - Fixed compatible typo "nxp,s32g2-stm" to "nxp,s32g2-stm-cnt"

	* v2
	  - Added Rob's tag
	  ** kbuild
	  - Reordered alphabetically the headers
	  - Added bitfield.h header
	  - Use DEFINE_SIMPLE_DEV_PM_OPS() and pm_sleep_ptr()

Daniel Lezcano (3):
  counters: Reorder the Makefile
  dt-bindings: counter: Add NXP System Timer Module Counter
  counter: Add STM based counter

 .../bindings/counter/nxp,s32g2-stm-cnt.yaml   |  64 +++
 arch/arm64/boot/dts/freescale/s32g2.dtsi      |   6 +-
 .../boot/dts/freescale/s32g274a-rdb2.dts      |  10 +-
 drivers/counter/Kconfig                       |  10 +
 drivers/counter/Makefile                      |  21 +-
 drivers/counter/nxp-stm-cnt.c                 | 433 ++++++++++++++++++
 6 files changed, 525 insertions(+), 19 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/counter/nxp,s32g2-stm-cnt.yaml
 create mode 100644 drivers/counter/nxp-stm-cnt.c

-- 
2.43.0