linux-kernel - Re: [PATCH v8 2/2] iio: adc: ad4130: add AD4130 driver

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Message-ID: <CACRpkdZ+KQqUKeevuXgcKLiK85STDeZFh=D47LMvyZb-o-Wbcw@mail.gmail.com>
Date:   Mon, 18 Jul 2022 15:26:22 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Cosmin Tanislav <demonsingur@...il.com>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Rob Herring <robh+dt@...nel.org>, linux-iio@...r.kernel.org,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org,
        Cosmin Tanislav <cosmin.tanislav@...log.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Subject: Re: [PATCH v8 2/2] iio: adc: ad4130: add AD4130 driver

Hi Cosmin,

thanks for your patch!

On Fri, Jul 15, 2022 at 6:50 AM Cosmin Tanislav <demonsingur@...il.com> wrote:

> AD4130-8 is an ultra-low power, high precision, measurement solution for
> low bandwidth battery operated applications.
>
> The fully integrated AFE (Analog Front-End) includes a multiplexer for up
> to 16 single-ended or 8 differential inputs, PGA (Programmable Gain
> Amplifier), 24-bit Sigma-Delta ADC, on-chip reference and oscillator,
> selectable filter options, smart sequencer, sensor biasing and excitation
> options, diagnostics, and a FIFO buffer.
>
> Signed-off-by: Cosmin Tanislav <cosmin.tanislav@...log.com>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
(...)
> +static int ad4310_parse_fw(struct iio_dev *indio_dev)
> +{
(...)
> +       int_clk_out = device_property_read_bool(dev, "adi,int-clk-out");
> +       if (st->mclk && int_clk_out)
> +               return dev_err_probe(dev, -EINVAL,
> +                                    "Cannot expose internal clock\n");
> +
> +       device_property_read_u32(dev, "adi,ext-clk-freq-hz", &ext_clk_freq);
> +       if (ext_clk_freq != AD4130_MCLK_FREQ_153_6KHZ &&
> +           ext_clk_freq != AD4130_MCLK_FREQ_76_8KHZ)
> +               return dev_err_probe(dev, -EINVAL,
> +                                    "Invalid external clock frequency %u\n",
> +                                    ext_clk_freq);

As mentioned in the bindings I think this is cheating. Just implement a real
clock abstraction and take the desired clock divider (1 or 2?) from the phandle.

See e.g.
commit 639d5661cc808057854681685ecb596406dbacce
"clk: ux500: Implement the missing CLKOUT clocks"
for an example, it is more complex so it should be a copy/paste/strip
exercise mostly.

Yours,
Linus Walleij