Re: [RFC v3 03/12] hte: Add tegra194 HTE kernel provider
From: Randy Dunlap <hidden>
Date: 2021-11-24 00:45:46
Also in:
linux-doc, linux-gpio, linux-tegra, lkml
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
quoted hunk ↗ jump to hunk
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? ----------- ^^^^^^
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+(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