From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Deepak R Varma <mh12gx2825@gmail.com>
Cc: outreachy-kernel@googlegroups.com,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Daniel Baluta <daniel.baluta@gmail.com>,
kieran.bingham@ideasonboard.com,
Lars-Peter Clausen <lars@metafoo.de>,
Michael Hennerich <Michael.Hennerich@analog.com>,
Jonathan Cameron <jic23@kernel.org>,
Hartmut Knaack <knaack.h@gmx.de>,
Peter Meerwald <pmeerw@pmeerw.net>,
linux-iio <linux-iio@vger.kernel.org>
Subject: Re: [PATCH v3 3/4] staging: iio: adc: ad7192: get_filter_freq code optimization
Date: Mon, 23 Mar 2020 01:44:20 +0200 [thread overview]
Message-ID: <CAHp75VfC=y1mHW5=ghwdMMZYg=00_a5RB0Phz4j_vM77pehvMA@mail.gmail.com> (raw)
In-Reply-To: <dad3cdb5de76234cc460300c31aea6af671f81ad.1584904896.git.mh12gx2825@gmail.com>
On Sun, Mar 22, 2020 at 9:57 PM Deepak R Varma <mh12gx2825@gmail.com> wrote:
>
> Current implementation of the function ad7192_get_available_filter_freq
> repeats calculation of output data rate a few times. We can simplify
> these steps by refactoring out the calculation of fADC. This would also
> addresses the checkpatch warning of line exceeding 80 character.
I'm not sure you did an equivalent changes. I believe in the original
code precision is better. Consider low clock frequencies when 10 bit
right shift may hide some bits of the division.
Care to write a python script to check the precision between old and new code?
...
> - /* Formulas for filter at page 25 of the datasheet */
> - fadc = DIV_ROUND_CLOSEST(st->fclk,
> - AD7192_SINC4_FILTER * AD7192_MODE_RATE(st->mode));
> - freq[0] = DIV_ROUND_CLOSEST(fadc * 240, 1024);
> + fadc = DIV_ROUND_CLOSEST(st->fclk, AD7192_MODE_RATE(st->mode) * 1024);
>
> - fadc = DIV_ROUND_CLOSEST(st->fclk,
> - AD7192_SINC3_FILTER * AD7192_MODE_RATE(st->mode));
> - freq[1] = DIV_ROUND_CLOSEST(fadc * 240, 1024);
> -
> - fadc = DIV_ROUND_CLOSEST(st->fclk, AD7192_MODE_RATE(st->mode));
> - freq[2] = DIV_ROUND_CLOSEST(fadc * 230, 1024);
> - freq[3] = DIV_ROUND_CLOSEST(fadc * 272, 1024);
> + /* Formulas for filter at page 25 of the datasheet */
> + freq[0] = DIV_ROUND_CLOSEST(fadc * 240, AD7192_SINC4_FILTER);
> + freq[1] = DIV_ROUND_CLOSEST(fadc * 240, AD7192_SINC3_FILTER);
> + freq[2] = fadc * 230;
> + freq[3] = fadc * 272;
--
With Best Regards,
Andy Shevchenko
next prev parent reply other threads:[~2020-03-22 23:44 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-22 19:53 [PATCH v3 0/4] staging: iio: adc: General code reformatting / cleanup patchset Deepak R Varma
2020-03-22 19:54 ` [PATCH v3 1/4] staging: iio: adc: ad7192: Re-indent enum labels Deepak R Varma
2020-03-24 7:18 ` Ardelean, Alexandru
2020-03-26 8:19 ` Ardelean, Alexandru
2020-03-26 8:22 ` Ardelean, Alexandru
2020-03-22 19:55 ` [PATCH v3 2/4] staging: iio: adc: ad7192: Correct macro names from SYNC to SINC Deepak R Varma
2020-03-22 23:40 ` Andy Shevchenko
2020-03-23 17:50 ` DEEPAK VARMA
2020-03-26 8:20 ` Ardelean, Alexandru
2020-03-22 19:56 ` [PATCH v3 3/4] staging: iio: adc: ad7192: get_filter_freq code optimization Deepak R Varma
2020-03-22 23:44 ` Andy Shevchenko [this message]
2020-03-23 0:49 ` [Outreachy kernel] " Stefano Brivio
2020-03-23 9:28 ` Andy Shevchenko
2020-03-23 12:15 ` Stefano Brivio
2020-03-23 17:52 ` DEEPAK VARMA
2020-03-24 8:06 ` Ardelean, Alexandru
2020-03-25 17:38 ` DEEPAK VARMA
2020-03-25 19:37 ` Andy Shevchenko
2020-03-25 19:59 ` Stefano Brivio
2020-03-26 8:15 ` Ardelean, Alexandru
2020-03-22 19:57 ` [PATCH v3 4/4] staging: iio: adc: ad7280a: Add comments to clarify stringified arguments Deepak R Varma
2020-03-24 8:07 ` Ardelean, Alexandru
2020-03-28 13:28 ` Jonathan Cameron
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