From: Peter Rosin <peda@axentia.se>
To: Andy Shevchenko <andy.shevchenko@gmail.com>,
Liam Beguin <liambeguin@gmail.com>
Cc: 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>
Subject: Re: [PATCH v12 07/16] iio: afe: rescale: add INT_PLUS_{MICRO,NANO} support
Date: Sun, 9 Jan 2022 21:20:09 +0100 [thread overview]
Message-ID: <8046b39f-28c1-7e46-e27c-6b9bc8824e21@axentia.se> (raw)
In-Reply-To: <CAHp75Vdi2bvCEtxpezt5L5JhO=8D+Za++CbQ8AximFaLnxnqyg@mail.gmail.com>
Hi!
On 2022-01-09 13:48, Andy Shevchenko wrote:
> On Sat, Jan 8, 2022 at 10:53 PM Liam Beguin <liambeguin@gmail.com> wrote:
>>
>> Some ADCs use IIO_VAL_INT_PLUS_{NANO,MICRO} scale types.
>> Add support for these to allow using the iio-rescaler with them.
>
> ...
>
>> + mult = scale_type == IIO_VAL_INT_PLUS_NANO ? GIGA : MEGA;
>> +
>> + /*
>> + * For IIO_VAL_INT_PLUS_{MICRO,NANO} scale types if either *val
>> + * OR *val2 is negative the schan scale is negative, i.e.
>> + * *val = 1 and *val2 = -0.5 yields -1.5 not -0.5.
>> + */
>> + neg = *val < 0 || *val2 < 0;
>> +
>> + tmp = (s64)abs(*val) * abs(rescale->numerator);
>> + *val = div_s64_rem(tmp, abs(rescale->denominator), &rem);
>> +
>> + tmp = (s64)rem * mult + (s64)abs(*val2) * abs(rescale->numerator);
>> + tmp = div_s64(tmp, abs(rescale->denominator));
>
> Isn't it too many repetitive abs() calls?
>
> What about
>
> // Create a macro and use for u16 (struct rn5t618_channel_ratios), s16
> (struct twl4030_prescale_divider_ratios), s32 (can be reused in struct
> rescale)
> struct u32_fract {
> u32 numerator;
> u32 denominator;
> };
> // (potential reuse in struct hclge_ptp_cycle) and so on...
>
> struct u32_fract fract = {
> .numerator = abs(rescale->numerator),
> .denominator = abs(rescale->denominator),
> };
>
> // obviously we can add a macro/inliner to abs() the fract struct and
> return original sign
>
> and reuse fract.numerator, fract.denominator?
This feels a bit excessive when the "problem" is two extra abs calls.
I don't think the code will get any easier to read by changing
abs(rescale->denominator) into fract.denominator and with my maintainer
hat on, I vote for just letting the compiler exercise its CSE engine.
Cheers,
Peter
next prev parent reply other threads:[~2022-01-09 20:20 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-08 20:53 [PATCH v12 00/16] iio: afe: add temperature rescaling support Liam Beguin
2022-01-08 20:53 ` [PATCH v12 01/16] iio: inkern: apply consumer scale on IIO_VAL_INT cases Liam Beguin
2022-01-08 20:53 ` [PATCH v12 02/16] iio: inkern: apply consumer scale when no channel scale is available Liam Beguin
2022-01-08 20:53 ` [PATCH v12 03/16] iio: inkern: make a best effort on offset calculation Liam Beguin
2022-01-08 20:53 ` [PATCH v12 04/16] iio: afe: rescale: use s64 for temporary scale calculations Liam Beguin
2022-01-08 20:53 ` [PATCH v12 05/16] iio: afe: rescale: reorder includes Liam Beguin
2022-01-08 20:53 ` [PATCH v12 06/16] iio: afe: rescale: expose scale processing function Liam Beguin
2022-01-09 13:07 ` Andy Shevchenko
2022-01-09 20:19 ` Peter Rosin
2022-01-09 20:25 ` Peter Rosin
2022-01-11 14:43 ` Liam Beguin
2022-01-11 14:35 ` Liam Beguin
2022-01-08 20:53 ` [PATCH v12 07/16] iio: afe: rescale: add INT_PLUS_{MICRO,NANO} support Liam Beguin
2022-01-09 12:48 ` Andy Shevchenko
2022-01-09 20:20 ` Peter Rosin [this message]
2022-01-11 14:33 ` Liam Beguin
2022-01-08 20:53 ` [PATCH v12 08/16] iio: afe: rescale: add offset support Liam Beguin
2022-01-08 20:53 ` [PATCH v12 09/16] iio: afe: rescale: fix accuracy for small fractional scales Liam Beguin
2022-01-09 13:02 ` Andy Shevchenko
2022-01-09 20:07 ` Peter Rosin
2022-01-08 20:53 ` [PATCH v12 10/16] iio: afe: rescale: reduce risk of integer overflow Liam Beguin
2022-01-08 20:53 ` [PATCH v12 11/16] iio: afe: rescale: make use of units.h Liam Beguin
2022-01-08 20:53 ` [PATCH v12 12/16] iio: test: add basic tests for the iio-rescale driver Liam Beguin
2022-01-08 20:53 ` [PATCH v12 13/16] iio: afe: rescale: add RTD temperature sensor support Liam Beguin
2022-01-08 20:53 ` [PATCH v12 14/16] iio: afe: rescale: add temperature transducers Liam Beguin
2022-01-08 20:53 ` [PATCH v12 15/16] dt-bindings: iio: afe: add bindings for temperature-sense-rtd Liam Beguin
2022-01-08 20:53 ` [PATCH v12 16/16] dt-bindings: iio: afe: add bindings for temperature transducers Liam Beguin
2022-01-09 13:10 ` [PATCH v12 00/16] iio: afe: add temperature rescaling support Andy Shevchenko
2022-01-30 14:39 ` Jonathan Cameron
2022-01-30 14:41 ` Jonathan Cameron
2022-01-30 14:59 ` Liam Beguin
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