linux-kernel - Re: [RFC 06/11] gpiolib: Add HTE support

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Message-ID: <CACRpkdb79ONmgBGh=YE9kXMa8_8_zCyyiPkg531NDCsX8jGx5Q@mail.gmail.com>
Date:   Sun, 27 Jun 2021 13:41:42 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Dipen Patel <dipenp@...dia.com>
Cc:     "thierry.reding@...il.com" <thierry.reding@...il.com>,
        Jon Hunter <jonathanh@...dia.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-tegra <linux-tegra@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Kent Gibson <warthog618@...il.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux Doc Mailing List <linux-doc@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [RFC 06/11] gpiolib: Add HTE support

On Sat, Jun 26, 2021 at 1:48 AM Dipen Patel <dipenp@...dia.com> wrote:

> Some GPIO chip can provide hardware timestamp support on its GPIO lines
> , in order to support that additional functions needs to be added which
> can talk to both GPIO chip and HTE (hardware timestamping engine)
> subsystem. This patch introduces functions which gpio consumer can use
> to request hardware assisted timestamping. Below is the list of the APIs
> that are added in gpiolib subsystem.
>
> - gpiod_hw_timestamp_control - to enable/disable HTE on specified GPIO
> line. This API will return HTE specific descriptor for the specified
> GPIO line during the enable call, it will be stored as pointer in the
> gpio_desc structure as hw_ts_data.
> - gpiod_is_hw_timestamp_enabled - to query if HTE is enabled on
> specified GPIO line.
> - gpiod_get_hw_timestamp - to retrieve hardware timestamps.
>
> Signed-off-by: Dipen Patel <dipenp@...dia.com>

This looks good to me.

The chip driver can look up and provide a timestamp provider for a
certain line, which is proper since the GPIO hardware will be tightly
coupled with the timestamp hardware so we need to ask the hardware
about this directly and delegate it to the GPIO driver.

Yours,
Linus Walleij