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

Bagas Sanjaya
2023-04-05T02:24:53Z

On 3/23/23 08:29, Dipen Patel wrote:
> 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(-)
>

While generalizing the doc, the doc file name should also be renamed
(i.e. to tegra-hte.rst).

> 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

The wording LGTM, thanks!

Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>

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