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 suggested 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. From RFC version 2 however, emulated threaded irq style implementation. - Discussed other possibility if HTE device can be added as posix clock type like PTP clocks. That was argued 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 clock source 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 is used as communication token between HTE subsystem and the provider. - Push timestamps to the subsystem. - Unregister itself on exit. Typical HTE consumer does following: - Initializes line attributes. - Obtains HTE descriptor. - 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 uses workqueue executing the secondary callback. - Release entity and its resources. HTE and GPIOLIB: - For the HTE provider which can timestamp GPIO lines. - For the userspace GPIO consumers, the GPIOLIB CDEV framework are extended as a frontend to the HTE. The kernel space consumers request GPIO lines directly to HTE subsystem. - 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. Changes in V3: - Corrected grammatical errors in HTE documentation and its bindings documents. - Removed multi-plural words in the HTE DT bindings. - Reflected changes done in DT bindings in the respective source codes. - Separated previous patch 07 into two patches in this series as 07 and 08. - Corrections in MAINTAINERS file. Changes in V4: - Removed hardware-timestamp-engine device tree property from gpio.txt. - Added hte_req_ts_by_linedata_ns. - Removed hte_req_ts_by_hte_name. - Renamed devm_of_hte_request_ts to devm_of_hte_request_ts_ns. - Corrected hte ts seqeunce counter handling in hte related code in gpiolib-cdev code. - Added line level detection in Tegra GPIO HTE provider. - Corrected GPIO line level calculation in gpiolib-cdev. Changes in V5: - Minor changes in dt-bindings. - Removed kernel thread in the HTE core. Changes in V6: - Changes in dt-bindings. - Added APIs in HTE core. - Merged tegra HTE test drivers. There are patches pending to add HTE provider for another Nvidia Tegra chip which will be pushed after this patch set. Dipen Patel (10): Documentation: Add HTE subsystem guide drivers: Add hardware timestamp engine (HTE) hte: Add tegra194 HTE kernel provider dt-bindings: Add HTE bindings 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 HTE test driver MAINTAINERS: Added HTE Subsystem .../hte/hardware-timestamps-common.yaml | 29 + .../devicetree/bindings/hte/hte-consumer.yaml | 39 + .../bindings/hte/nvidia,tegra194-hte.yaml | 88 ++ Documentation/hte/hte.rst | 77 ++ Documentation/hte/index.rst | 22 + Documentation/hte/tegra194-hte.rst | 47 + Documentation/index.rst | 1 + MAINTAINERS | 8 + drivers/Kconfig | 2 + drivers/Makefile | 1 + drivers/gpio/gpio-tegra186.c | 81 +- drivers/gpio/gpiolib-cdev.c | 252 ++++- drivers/gpio/gpiolib.c | 58 ++ drivers/gpio/gpiolib.h | 1 + drivers/hte/Kconfig | 33 + drivers/hte/Makefile | 3 + drivers/hte/hte-tegra194-test.c | 239 +++++ drivers/hte/hte-tegra194.c | 730 ++++++++++++++ drivers/hte/hte.c | 948 ++++++++++++++++++ include/linux/gpio/consumer.h | 16 +- include/linux/gpio/driver.h | 10 + include/linux/hte.h | 272 +++++ include/uapi/linux/gpio.h | 3 + tools/gpio/gpio-event-mon.c | 6 +- 24 files changed, 2929 insertions(+), 37 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-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: c2528a0cdebd8ba7ef30e0655f8ea89f34c3a633 -- 2.17.1
