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References: <20231018182943.18700-1-ddrokosov@salutedevices.com> <20231018182943.18700-3-ddrokosov@salutedevices.com>
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From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Thu, 19 Oct 2023 11:56:54 +0300
Message-ID: <CAHp75VcyvEdkzx4emYwssdYuqAiPdx5iqc-tY74_ebZfLKKM3A@mail.gmail.com>
Subject: Re: [PATCH v2 02/11] leds: aw200xx: support HWEN hardware control
To:     Dmitry Rokosov <ddrokosov@salutedevices.com>
Cc:     lee@kernel.org, pavel@ucw.cz, robh+dt@kernel.org,
        krzysztof.kozlowski+dt@linaro.org, conor+dt@kernel.org,
        kernel@sberdevices.ru, rockosov@gmail.com,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-leds@vger.kernel.org
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On Wed, Oct 18, 2023 at 9:29=E2=80=AFPM Dmitry Rokosov
<ddrokosov@salutedevices.com> wrote:
>
> HWEN is hardware control, which is used for enable/disable aw200xx chip.
> It's high active, internally pulled down to GND.
>
> After HWEN pin set high the chip begins to load the OTP information,
> which takes 200us to complete. About 200us wait time is needed for
> internal oscillator startup and display SRAM initialization. After
> display SRAM initialization, the registers in page 1 to page 5 can be
> configured via i2c interface.

Is there any Documentation update for this new binding?

...

> +       chip->hwen =3D devm_gpiod_get_optional(&client->dev, "hwen", GPIO=
D_OUT_HIGH);

With _optional APIs we distinguish 3 cases: found, not found, error.
And error can be (among others) the deferred probe, meaning that GPIO
_is coming_. Hence the rule of thumb for the _optional() APIs is to
check for error and bail out on that condition (note, it's applicable
to any _optional() APIs, not limited by GPIO library).

...

>         aw200xx_chip_reset(chip);
> +       aw200xx_disable(chip);

It seems it can be modeled as a (GPIO) regulator. At least many
drivers do so, but I leave this to the maintainers to decide.

--=20
With Best Regards,
Andy Shevchenko