linux-kernel - Re: [PATCH v2 2/3] iio: chemical: Add support for external Reset and Wakeup in CCS811

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Date:   Tue, 14 Apr 2020 19:42:24 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     mani@...nel.org
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Rob Herring <robh+dt@...nel.org>, narcisaanamaria12@...il.com,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald <pmeerw@...erw.net>,
        linux-iio <linux-iio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] iio: chemical: Add support for external Reset and
 Wakeup in CCS811

On Tue, Apr 14, 2020 at 6:34 PM <mani@...nel.org> wrote:
>
> From: Manivannan Sadhasivam <mani@...nel.org>
>
> CCS811 VOC sensor exposes nRESET and nWAKE pins which can be connected
> to GPIO pins of the host controller. These pins can be used to externally
> release the device from reset and also to wake it up before any I2C
> transaction. The initial driver support assumed that the nRESET pin is not
> connected and the nWAKE pin is tied to ground.
>
> This commit improves it by adding support for controlling those two pins
> externally using a host controller. For the case of reset, if the hardware
> reset is not available, the mechanism to do software reset is also added.
>
> As a side effect of doing this, the IIO device allocation needs to be
> slightly moved to top of probe to make use of priv data early.

Thank you for an update, my comments below.

...

> +       reset_gpio = devm_gpiod_get_optional(&client->dev, "reset",
> +                                            GPIOD_OUT_LOW);
> +       if (IS_ERR(reset_gpio)) {

> +               dev_err(&client->dev, "Failed to acquire reset gpio\n");

If it's a deferred probe, it would spam the log.

> +               return PTR_ERR(reset_gpio);
> +       }

...

> +               static const u8 reset_seq[] = {
> +                       0xFF, 0x11, 0xE5, 0x72, 0x8A,
> +               };

I would suggest to comment above from where you got this and the
meaning of the numbers.

...

> +       data->wakeup_gpio = devm_gpiod_get_optional(&client->dev, "wakeup",
> +                                                   GPIOD_OUT_HIGH);
> +       if (IS_ERR(data->wakeup_gpio)) {

> +               dev_err(&client->dev, "Failed to acquire wakeup gpio\n");

Ditto.

> +               return PTR_ERR(data->wakeup_gpio);
> +       }

-- 
With Best Regards,
Andy Shevchenko