Messages in this thread Patch in this message | | | Subject | Re: [RFC v3 03/12] hte: Add tegra194 HTE kernel provider | From | Randy Dunlap <> | Date | Tue, 23 Nov 2021 16:45:37 -0800 |
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Hi--
On 11/23/21 11:30 AM, Dipen Patel wrote: > Tegra194 device has multiple HTE instances also known as GTE > (Generic hardware Timestamping Engine) which can timestamp subset of > SoC lines/signals. This provider driver focuses on IRQ and GPIO lines > and exposes timestamping ability on those lines to the consumers > through HTE subsystem. > > Also, with this patch, added: > - documentation about this provider and its capabilities at > Documentation/hte. > - Compilation support in Makefile and Kconfig > > Signed-off-by: Dipen Patel <dipenp@nvidia.com> > --- > Changes in v3: > - Addressed grammatical/spelling errors. > > Documentation/hte/index.rst | 22 ++ > Documentation/hte/tegra194-hte.rst | 57 +++ > Documentation/index.rst | 1 + > drivers/hte/Kconfig | 12 + > drivers/hte/Makefile | 1 + > drivers/hte/hte-tegra194.c | 545 +++++++++++++++++++++++++++++ > 6 files changed, 638 insertions(+) > create mode 100644 Documentation/hte/index.rst > create mode 100644 Documentation/hte/tegra194-hte.rst > create mode 100644 drivers/hte/hte-tegra194.c >
> diff --git a/Documentation/hte/tegra194-hte.rst b/Documentation/hte/tegra194-hte.rst > new file mode 100644 > index 000000000000..3bebcbac5847 > --- /dev/null > +++ b/Documentation/hte/tegra194-hte.rst > @@ -0,0 +1,57 @@ > +HTE Kernel provider driver > +========================== > + > +Description > +----------- > +The Nvidia tegra194 HTE provider driver implements two GTE > +(Generic Timestamping Engine) instances: 1) GPIO GTE and 2) LIC > +(Legacy Interrupt Controller) IRQ GTE. Both GTEs instances get the
Both GTE instances
> +timestamp from the system counter TSC which has 31.25MHz clock rate, and the > +driver converts clock tick rate to nanoseconds before storing it as timestamp > +value. > + > +GPIO GTE > +-------- > + > +This GTE instance timestamps GPIO in real time. For that to happen GPIO > +needs to be configured as input and IRQ needs to be enabled. The only always on
Is "only" supposed to be here? ----------- ^^^^^^
> +(AON) GPIO controller instance supports timestamping GPIOs in real time and it > +has 39 GPIO lines. The GPIO GTE and AON GPIO controller are tightly coupled as > +it requires very specific bits to be set in GPIO config register before GPIO > +GTE can be used. The GPIO GTE functionality is accessed from the GPIOLIB > +framework for the in-kernel and userspace consumers. In the latter case, > +requests go through GPIOLIB CDEV framework. The below APIs are added in GPIOLIB > +framework to access HTE subsystem and GPIO GTE. > + > +.. kernel-doc:: drivers/gpio/gpiolib.c > + :functions: gpiod_req_hw_timestamp_ns gpiod_rel_hw_timestamp_ns > + > +There is hte-tegra194-gpio-test.c, located in ``drivers/hte/`` directory, test > +driver which demonstrates above APIs for the Jetson AGX platform. > + > +For userspace consumers, GPIO_V2_LINE_FLAG_EVENT_CLOCK_HARDWARE flag must be > +specified during IOCTL calls. Refer to ``tools/gpio/gpio-event-mon.c``, which > +returns the timestamp in nanoseconds. > + > +LIC (Legacy Interrupt Controller) IRQ GTE > +----------------------------------------- > + > +This GTE instance timestamps LIC IRQ lines in real time. There are 352 IRQ > +lines which this instance can add timestamps to in real time. The hte > +devicetree binding described at ``Documentation/devicetree/bindings/hte/`` > +provides an example of how a consumer can request an IRQ line. Since it is a > +one-to-one mapping, consumers can simply specify the IRQ number that they are > +interested in. There is no userspace consumer support for this GTE instance in > +the hte framework. The sample test code hte-tegra194-irq-test.c, located in > +the ``drivers/hte/`` directory, demonstrates how to use an IRQ GTE instance. > +The below is sample device tree snippet code for the test driver:: > + > + tegra_hte_irq_test { > + compatible = "nvidia,tegra194-hte-irq-test"; > + htes = <&tegra_hte_lic 0x19>; > + hte-names = "hte-lic"; > + }; > + > +The provider source code of both IRQ and GPIO GTE instances is located at > +``drivers/hte/hte-tegra194.c``. > + > diff --git a/Documentation/index.rst b/Documentation/index.rst > index 1b13c2445e87..b41118577fe6 100644 > --- a/Documentation/index.rst > +++ b/Documentation/index.rst > @@ -138,6 +138,7 @@ needed). > misc-devices/index > scheduler/index > mhi/index > + hte/index
Looks like a text alignment problem there.
> > Architecture-agnostic documentation > -----------------------------------
-- ~Randy
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