| Message ID | 20210625235532.19575-1-dipenp@nvidia.com |
|---|---|
| Headers | show |
| Series | Intro to Hardware timestamping engine | expand |
On Sat, Jun 26, 2021 at 2:48 AM Dipen Patel <dipenp@nvidia.com> wrote: > > 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 with subsystem 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 same at > https://lore.kernel.org/lkml/4c46726d-fa35-1a95-4295-bca37c8b6fe3@nvidia.com/ > > 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. I guess this series should include more people from different companies, especially documentation parts. This may be used by different hardware and quite different vendors. Developing a framework like this for only one vendor is no go in general. > This patch series implements and extends GPIOLIB 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. > - 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 callbacks and > optional get_clk_src_info callback 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. The HTE > subsystem stores it into software buffer for the consumers. > - Unregister itself > > Typical HTE consumer does following: > - Request interested entity it wishes to timestamp in realtime to the > subsystem. During this call HTE subsystem allocates software buffer to > store timestamps data. > - 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. > - It can optionally specify callback during registration, this cb will > be called when provider pushes timestamps. Once notified through cb, the > consumer can call retrieve API to read the data from the software buffer. > If cb is not provided, the consumers can elect to call blocking version of > retrieve API. > - Manage pre allocated software buffer if needed. It includes changing buffer > length and watermark/threshold. The subsystem automatically sets watermark or > threshold at 1, consumers can later change it to any other value it wishes. The > main purpose for having threshold functionality is to notify consumer either > through callback if provided or unblock waiting consumer when threshold is > reached. > - Retrieve timestamp using various means provided by subsystem. > - 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 also known as GTE > (Generic Timestamping Engine). The tegra gpio driver is modified to accommodate > HTE functionality. > > Dipen Patel (11): > Documentation: Add HTE subsystem guide > drivers: Add HTE subsystem > 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 + > .../devicetree/bindings/hte/hte-consumer.yaml | 47 + > .../devicetree/bindings/hte/hte.yaml | 34 + > .../bindings/hte/nvidia,tegra194-hte.yaml | 83 + > Documentation/hte/hte.rst | 198 +++ > Documentation/hte/index.rst | 21 + > Documentation/hte/tegra194-hte.rst | 65 + > Documentation/index.rst | 1 + > MAINTAINERS | 8 + > drivers/Kconfig | 2 + > drivers/Makefile | 1 + > drivers/gpio/gpio-tegra186.c | 78 + > drivers/gpio/gpiolib-cdev.c | 65 +- > drivers/gpio/gpiolib.c | 92 ++ > drivers/gpio/gpiolib.h | 11 + > drivers/hte/Kconfig | 49 + > drivers/hte/Makefile | 4 + > drivers/hte/hte-tegra194-gpio-test.c | 255 +++ > drivers/hte/hte-tegra194-irq-test.c | 400 +++++ > drivers/hte/hte-tegra194.c | 554 +++++++ > drivers/hte/hte.c | 1368 +++++++++++++++++ > include/linux/gpio/consumer.h | 21 +- > include/linux/gpio/driver.h | 13 + > include/linux/hte.h | 278 ++++ > include/uapi/linux/gpio.h | 1 + > tools/gpio/gpio-event-mon.c | 6 +- > 26 files changed, 3657 insertions(+), 5 deletions(-) > create mode 100644 Documentation/devicetree/bindings/hte/hte-consumer.yaml > create mode 100644 Documentation/devicetree/bindings/hte/hte.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 > > -- > 2.17.1 > -- With Best Regards, Andy Shevchenko