Hi Randy,

Thanks for the comments. I will implement changes in RFC V3.

Best Regards,

Dipen Patel

On 10/1/21 5:07 PM, Randy Dunlap wrote:

On 9/30/21 4:26 PM, Dipen Patel wrote:

quoted

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"

quoted

+both GTEs instances get the timestamp from the system counter TSC which has

   Both

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+31.25MHz clock rate, and the driver converts clock tick rate to nano seconds

                                                                   nanoseconds

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+before storing it as timestamp value.
+
+GPIO GTE
+--------
+
+This GTE instance timestamps GPIO in real time, for that to happen GPIO

                                             time. For

quoted

+needs to be configured as input and IRQ needs to ba enabled. The only always on

                                                    be

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+(AON) gpio controller instance supports timestamping GPIOs in realtime and it

         GPIO                                                    real time {or change
                           the instance 3 lines above to be "realtime"}

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+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

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+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

quoted

+returns the timestamp in nano second.

                            nanoseconds.

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+
+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")

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+lines which this instance can help timestamp realtime. The hte devicetree

                             can add timestamps to in realtime.

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+binding described at ``Documentation/devicetree/bindings/hte/`` gives out

                                                                   provides an

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+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,

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+consumers can simply specify IRQ number that they are interested in. There is

                        specify the IRQ number

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+no userspace consumer support for this GTE instance. The sample test code
+hte-tegra194-irq-test.c, located in ``drivers/hte/`` directory,

                                    in the

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+demonstrates how to use IRQ GTE instance. The below is sample device tree

                how to use an IRQ GTE instance.

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+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

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+``drivers/hte/hte-tegra194.c``.
+