[PATCH V4 06/10] hte: Re-phrase tegra API document

Dipen Patel
2023-03-23T01:30:13Z

Make Tegra194 API document generic to make it applicable for
current and future tegra hte providers.

Signed-off-by: Dipen Patel <dipenp@nvidia.com>
---
Documentation/driver-api/hte/tegra194-hte.rst | 33 +++++++++----------
1 file changed, 16 insertions(+), 17 deletions(-)

diff --git a/Documentation/driver-api/hte/tegra194-hte.rst b/Documentation/driver-api/hte/tegra194-hte.rst
index f2d617265546..85e654772782 100644
--- a/Documentation/driver-api/hte/tegra194-hte.rst
+++ b/Documentation/driver-api/hte/tegra194-hte.rst
@@ -5,25 +5,25 @@ 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 GTE instances get the
-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.
+The Nvidia tegra HTE provider also known as GTE (Generic Timestamping Engine)
+driver implements two GTE instances: 1) GPIO GTE and 2) LIC
+(Legacy Interrupt Controller) IRQ GTE. Both GTE instances get the 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. The always on (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, for that GPIOLIB
-adds two optional APIs as below. The GPIO GTE code supports both kernel
-and userspace consumers. The kernel space consumers can directly talk to HTE
-subsystem while userspace consumers timestamp requests go through GPIOLIB CDEV
-framework to HTE subsystem.
+needs to be configured as input. Only the always on (AON) GPIO controller
+instance supports timestamping GPIOs in real time as it is tightly coupled with
+the GPIO GTE. To support this, GPIOLIB adds two optional APIs as mentioned
+below. The GPIO GTE code supports both kernel and userspace consumers. The
+kernel space consumers can directly talk to HTE subsystem while userspace
+consumers timestamp requests go through GPIOLIB CDEV framework to HTE
+subsystem. The hte devicetree binding described at
+``Documentation/devicetree/bindings/timestamp`` provides an example of how a
+consumer can request an GPIO line.

See gpiod_enable_hw_timestamp_ns() and gpiod_disable_hw_timestamp_ns().

@@ -34,9 +34,8 @@ 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/timestamp``
+This GTE instance timestamps LIC IRQ lines in real time. The hte devicetree
+binding described at ``Documentation/devicetree/bindings/timestamp``
provides an example of how a consumer can request an IRQ line. Since it is a
one-to-one mapping with IRQ GTE provider, consumers can simply specify the IRQ
number that they are interested in. There is no userspace consumer support for
--
2.17.1