linux-kernel - Re: [PATCH 5/7] hte: Re-phrase tegra API document

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Date:   Sat, 5 Nov 2022 10:33:35 +0700
From:   Bagas Sanjaya <bagasdotme@...il.com>
To:     Dipen Patel <dipenp@...dia.com>
Cc:     thierry.reding@...il.com, jonathanh@...dia.com,
        linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-gpio@...r.kernel.org, linus.walleij@...aro.org,
        devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
        robh+dt@...nel.org
Subject: Re: [PATCH 5/7] hte: Re-phrase tegra API document

On Thu, Nov 03, 2022 at 10:45:21AM -0700, Dipen Patel wrote:
>  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().
>  

I think the wording can be better:

---- >8 ----

diff --git a/Documentation/driver-api/hte/tegra194-hte.rst b/Documentation/driver-api/hte/tegra194-hte.rst
index 85e654772782c1..13c45bfc03a75e 100644
--- a/Documentation/driver-api/hte/tegra194-hte.rst
+++ b/Documentation/driver-api/hte/tegra194-hte.rst
@@ -5,11 +5,11 @@ HTE Kernel provider driver
 
 Description
 -----------
-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.
+The Nvidia tegra HTE provider, also known as GTE (Generic Timestamping Engine)
+driver implements two GTE instances: GPIO GTE and LIC (Legacy Interrupt
+Controller) IRQ GTE. Both GTE instances get the timestamp from 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
 --------
@@ -19,17 +19,17 @@ 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.
+kernel space consumers can directly talk to HTE subsystem while requests from
+userspace consumers 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().
+To toggle hardware timestamp, use gpiod_enable_hw_timestamp_ns() and
+gpiod_disable_hw_timestamp_ns().
 
 For userspace consumers, GPIO_V2_LINE_FLAG_EVENT_CLOCK_HTE flag must be
-specified during IOCTL calls. Refer to ``tools/gpio/gpio-event-mon.c``, which
-returns the timestamp in nanoseconds.
+specified during IOCTL calls. Refer to ``tools/gpio/gpio-event-mon.c`` for
+example.
 
 LIC (Legacy Interrupt Controller) IRQ GTE
 -----------------------------------------

Thanks.

-- 
An old man doll... just what I always wanted! - Clara

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