linux-kernel - Re: [PATCH v5 01/11] Documentation: Add HTE subsystem guide

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Date:   Tue, 29 Mar 2022 15:36:46 -0700
From:   Dipen Patel <dipenp@...dia.com>
To:     Bagas Sanjaya <bagasdotme@...il.com>, thierry.reding@...il.com,
        jonathanh@...dia.com, smangipudi@...dia.com,
        linux-kernel@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-gpio@...r.kernel.org, linus.walleij@...aro.org,
        bgolaszewski@...libre.com, warthog618@...il.com,
        devicetree@...r.kernel.org, linux-doc@...r.kernel.org,
        robh+dt@...nel.org
Subject: Re: [PATCH v5 01/11] Documentation: Add HTE subsystem guide

Hi Sanjaya,

I will address your comments in next patch version.  Thanks for the comment.

Best,

Dipen Patel

On 3/29/22 6:16 AM, Bagas Sanjaya wrote:
> On 29/03/22 12.45, Dipen Patel wrote:
>> +============================================
>> +The Linux Hardware Timestamping Engine (HTE)
>> +============================================
>> +
>> +:Author: Dipen Patel
>> +
>
> Please learn how to convey semantics with rst format, see further comments
> below.
>
>> +This document describes the API that can be used by hardware timestamping
>> +engine provider and consumer drivers that want to use the hardware timestamping
>> +engine (HTE) framework. Both consumers and providers must include
>> +#include <linux/hte.h>.
>> +
>
> Maybe it's better to write as `... providers must ``#include <linux/hte.h>```.
>
>> +The HTE framework APIs for the providers
>> +----------------------------------------
>> +
>> +.. kernel-doc:: drivers/hte/hte.c
>> +   :functions: devm_hte_register_chip hte_push_ts_ns
>> +
>> +The HTE framework APIs for the consumers
>> +----------------------------------------
>> +
>> +.. kernel-doc:: drivers/hte/hte.c
>> +   :functions: devm_of_hte_request_ts_ns hte_req_ts_by_linedata_ns hte_release_ts hte_enable_ts hte_disable_ts hte_get_clk_src_info
>> +
>> +The HTE framework public structures
>> +-----------------------------------
>> +.. kernel-doc:: include/linux/hte.h
>> +
>> +More on the HTE timestamp data
>> +------------------------------
>> +The struct hte_ts_data is used to pass timestamp details between the consumers
>> +and the providers. It expresses timestamp data in nanoseconds in u64 data
>> +type. For now all the HTE APIs using struct hte_ts_data require tsc to be in
>> +nanoseconds. An example of the typical hte_ts_data data life cycle, for the
>> +GPIO line is as follows::
>> +
>
> When we talk about name terms found in actual code (like keywords or variable
> names), it is customary to enclose them inside inline code (for example,
> ``struct what`` or ``u64 what``).
>
>> + - Monitors GPIO line change.
>> + - Detects the state change on GPIO line.
>> + - Converts timestamps in nanoseconds and stores it in tsc.
>> + - Stores GPIO raw level in raw_level variable if the provider has that
>> + hardware capability.
>> + - Pushes this hte_ts_data object to HTE subsystem.
>> + - HTE subsystem increments seq counter and invokes consumer provided callback.
>> + Based on callback return value, the HTE core invokes secondary callback in
>> + the thread context.
>> +
>> +HTE subsystem debugfs attributes
>> +--------------------------------
>> +HTE subsystem creates debugfs attributes at ``/sys/kernel/debug/hte/``.
>> +It also creates line/signal-related debugfs attributes at
>> +``/sys/kernel/debug/hte/<provider>/<label or line id>/``.
>> +
>> +`ts_requested`
>> +        The total number of entities requested from the given provider,
>> +        where entity is specified by the provider and could represent
>> +        lines, GPIO, chip signals, buses etc...
>> +                The attribute will be available at
>> +        ``/sys/kernel/debug/hte/<provider>/``.
>> +
>> +        Read-only value
>> +
>> +`total_ts`
>> +        The total number of entities supported by the provider.
>> +                The attribute will be available at
>> +        ``/sys/kernel/debug/hte/<provider>/``.
>> +
>> +        Read-only value
>> +
>> +`dropped_timestamps`
>> +        The dropped timestamps for a given line.
>> +                The attribute will be available at
>> +        ``/sys/kernel/debug/hte/<provider>/<label or line id>/``.
>> +
>> +        Read-only value
>
> Since all these debugfs variables are read-only, we can say "Note that all
> these values are read-only".
>