Messages in this thread | | | Subject | Re: [RFC v2 03/11] hte: Add tegra194 HTE kernel provider | From | Randy Dunlap <> | Date | Fri, 1 Oct 2021 17:07:02 -0700 |
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On 9/30/21 4:26 PM, Dipen Patel wrote: > diff --git a/Documentation/hte/tegra194-hte.rst b/Documentation/hte/tegra194-hte.rst > new file mode 100644 > index 000000000000..fb229bda2408 > --- /dev/null > +++ b/Documentation/hte/tegra194-hte.rst > @@ -0,0 +1,56 @@ > +HTE Kernel provider driver > +========================== > + > +Description > +----------- > +The Nvidia tegra194 HTE provider driver implements two GTE > +(Generic Timestamping Engine) instances 1) GPIO GTE and 2) LIC IRQ GTE. The
instances: ^^Drop "The"
> +both GTEs instances get the timestamp from the system counter TSC which has
Both
> +31.25MHz clock rate, and the driver converts clock tick rate to nano seconds
nanoseconds
> +before storing it as timestamp value. > + > +GPIO GTE > +-------- > + > +This GTE instance timestamps GPIO in real time, for that to happen GPIO
time. For
> +needs to be configured as input and IRQ needs to ba enabled. The only always on
be
> +(AON) gpio controller instance supports timestamping GPIOs in realtime and it
GPIO real time {or change the instance 3 lines above to be "realtime"}
> +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 later case,
in-kernel latter
> +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 > +specifed during IOCTL calls, refer ``tools/gpio/gpio-event-mon.c``, which
specified calls. Refer to
> +returns the timestamp in nano second.
nanoseconds.
> + > +LIC IRQ GTE > +----------- > + > +This GTE instance timestamp LIC IRQ lines in real time. There are 352 IRQ
timestamps ^^^^^^^^^ {be consistent} (also (repeating a prior email) define "LIC")
> +lines which this instance can help timestamp realtime. The hte devicetree
can add timestamps to in realtime.
> +binding described at ``Documentation/devicetree/bindings/hte/`` gives out
provides an
> +example how consumer can request IRQ line, since it is one to one mapping,
example of how a consumer can request an IRQ line. Since it is a one-to-one mapping,
> +consumers can simply specify IRQ number that they are interested in. There is
specify the IRQ number
> +no userspace consumer support for this GTE instance. The sample test code > +hte-tegra194-irq-test.c, located in ``drivers/hte/`` directory,
in the
> +demonstrates how to use IRQ GTE instance. The below is sample device tree
how to use an IRQ GTE instance.
> +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 locate at
located
> +``drivers/hte/hte-tegra194.c``. > +
-- ~Randy
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