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References: <20211222034646.222189-1-liambeguin@gmail.com> <20211222034646.222189-9-liambeguin@gmail.com>
In-Reply-To: <20211222034646.222189-9-liambeguin@gmail.com>
From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Wed, 22 Dec 2021 14:27:01 +0200
Message-ID: <CAHp75VdonriGKBQz=pnJboPZ=HPfuYSakEGCorBath5iBxfX_Q@mail.gmail.com>
Subject: Re: [PATCH v11 08/15] iio: afe: rescale: fix accuracy for small
 fractional scales
To:     Liam Beguin <liambeguin@gmail.com>
Cc:     Peter Rosin <peda@axentia.se>, Jonathan Cameron <jic23@kernel.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        linux-iio <linux-iio@vger.kernel.org>,
        devicetree <devicetree@vger.kernel.org>,
        Rob Herring <robh+dt@kernel.org>
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On Wed, Dec 22, 2021 at 5:47 AM Liam Beguin <liambeguin@gmail.com> wrote:
>
> From: Liam Beguin <lvb@xiphos.com>
>
> The approximation caused by integer divisions can be costly on smaller
> scale values since the decimal part is significant compared to the
> integer part. Switch to an IIO_VAL_INT_PLUS_NANO scale type in such
> cases to maintain accuracy.

...

> -               tmp = div_s64(tmp, 1000000000LL);
> +
> +               tmp = div_s64_rem(tmp, 1000000000LL, &rem);
>                 *val = tmp;

> -               return scale_type;
> +

It seems you may add this blank line to one of the previous patches, may you?

> +               if (!rem)
> +                       return scale_type;

-- 
With Best Regards,
Andy Shevchenko