This patch series introduces new subsystem called hardware timestamping engine (HTE). It offers functionality such as timestamping through hardware means in realtime. The HTE subsystem centralizes HTE provider and consumers where providers can register themselves and the consumers can request interested entity which could be lines, GPIO, signals or buses. The HTE subsystem provides timestamp in nano seconds, having said that the provider need to convert the timestamp if its not in that unit. There was upstream discussion about the HTE at https://lore.kernel.org/lkml/4c46726d-fa35-1a95-4295-bca37c8b6fe3@xxxxxxxxxx/ To summarize upstream discussion: - It was heavily favoured by Linus and Kent to extend GPIOLIB and supporting GPIO drivers to add HTE functionality and I agreed to experiment with it. This patch series implements and extends GPIOLIB, GPIOLIB-CDEV and GPIO tegra driver. - Discussed possibility to add HTE provider as irqchip instead which was argued against as HTE devices are not necessarily event emitting devices. This RFC version 2 however tries to emulate threaded irq style implementation. - Discussed other possibility if HTE device can be added as posix clock type like PTP clocks. That was also argues against since HTE devices are not necessarily tightly coupled with hardware clock. Typical HTE provider does following: - Register itself with HTE subsystem - Provide request, release, enable, disable timestamp and get_clk_src_info callbacks to HTE subsystem. - Provide optional xlate callback to the subsystem which can translate consumer provided logical ids into actual ids of the entity, where entity here is the provider dependent and could be GPIO, in chip lines or signals, buses etc...This converted id will be used between HTE subsystem and the provider for below bullet point. - Push timestamps to the subsystem. This happens when HTE provider has timestamp data available and willing to push it to HTE subsystem. - Unregister itself on exit. Typical HTE consumer does following: - Request interested entity it wishes to timestamp in realtime to the subsystem. - The subsystem does necessary communications with the provider to complete the request, which includes translating logical id of the entity to provider dependent physical/actual id and enabling hardware timestamping on requested id. - The request includes callbacks, it will be used to push timestamps. Optionally, the consumer can provided threaded callback, if specified, the HTE subsystem will create kernel thread responsible executing the threaded callback. - Release entity and its resources. HTE and GPIOLIB: - For the HTE provider which can timestamp GPIO lines. - For the GPIO consumers, either in kernel or userspace, The GPIOLIB and its CDEV framework are extended as frontend to the HTE by introducing new APIs. - Tegra194 AON GPIO controller has HTE support known as GTE (Generic Timestamping Engine). The tegra gpio driver is modified to accommodate HTE functionality. Changes in V2: - Removed buffer management and related APIs from the HTE core. - Removed timestamp retrieve APIs from the HTE core. - Modified request API with two callbacks, second callback is invoked in thread context and is optional, while first callback is mandatory and used to push timestamp data to consumers. - Replaced hte with hardware-timestamping in DT bindings as hte appeared too short according to review comments. Dipen Patel (11): Documentation: Add HTE subsystem guide drivers: Add hardware timestamp engine (HTE) hte: Add tegra194 HTE kernel provider dt-bindings: Add HTE bindings hte: Add Tegra194 IRQ HTE test driver gpiolib: Add HTE support gpio: tegra186: Add HTE in gpio-tegra186 driver gpiolib: cdev: Add hardware timestamp clock type tools: gpio: Add new hardware clock type hte: Add tegra GPIO HTE test driver MAINTAINERS: Added HTE Subsystem .../bindings/gpio/nvidia,tegra186-gpio.txt | 7 + .../hte/hardware-timestamps-common.yaml | 29 + .../devicetree/bindings/hte/hte-consumer.yaml | 48 + .../bindings/hte/nvidia,tegra194-hte.yaml | 79 ++ Documentation/hte/hte.rst | 83 ++ Documentation/hte/index.rst | 22 + Documentation/hte/tegra194-hte.rst | 56 ++ Documentation/index.rst | 1 + MAINTAINERS | 8 + drivers/Kconfig | 2 + drivers/Makefile | 1 + drivers/gpio/gpio-tegra186.c | 89 ++ drivers/gpio/gpiolib-cdev.c | 161 +++- drivers/gpio/gpiolib.c | 73 ++ drivers/gpio/gpiolib.h | 12 + drivers/hte/Kconfig | 50 + drivers/hte/Makefile | 5 + drivers/hte/hte-tegra194-gpio-test.c | 252 +++++ drivers/hte/hte-tegra194-irq-test.c | 169 ++++ drivers/hte/hte-tegra194.c | 554 +++++++++++ drivers/hte/hte.c | 907 ++++++++++++++++++ include/linux/gpio/consumer.h | 19 +- include/linux/gpio/driver.h | 14 + include/linux/hte.h | 248 +++++ include/uapi/linux/gpio.h | 1 + tools/gpio/gpio-event-mon.c | 6 +- 26 files changed, 2884 insertions(+), 12 deletions(-) create mode 100644 Documentation/devicetree/bindings/hte/hardware-timestamps-common.yaml create mode 100644 Documentation/devicetree/bindings/hte/hte-consumer.yaml create mode 100644 Documentation/devicetree/bindings/hte/nvidia,tegra194-hte.yaml create mode 100644 Documentation/hte/hte.rst create mode 100644 Documentation/hte/index.rst create mode 100644 Documentation/hte/tegra194-hte.rst create mode 100644 drivers/hte/Kconfig create mode 100644 drivers/hte/Makefile create mode 100644 drivers/hte/hte-tegra194-gpio-test.c create mode 100644 drivers/hte/hte-tegra194-irq-test.c create mode 100644 drivers/hte/hte-tegra194.c create mode 100644 drivers/hte/hte.c create mode 100644 include/linux/hte.h base-commit: 2d02a18f75fc81177a4e30f3aaaed9af06cc3adc -- 2.17.1
