linux-kernel - Re: [PATCH v4] iio: adc: stm32: add oversampling support

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Message-ID: <CAHp75VfUkStzq4zrKkaQ67REuuTSGhoD9o1LXU-YohUULBnd=w@mail.gmail.com>
Date: Sat, 12 Apr 2025 21:07:41 +0300
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Olivier Moysan <olivier.moysan@...s.st.com>, David Lechner <dlechner@...libre.com>, 
	Nuno Sá <nuno.sa@...log.com>, 
	Andy Shevchenko <andy@...nel.org>, Maxime Coquelin <mcoquelin.stm32@...il.com>, 
	Alexandre Torgue <alexandre.torgue@...s.st.com>, 
	Fabrice Gasnier <fabrice.gasnier@...s.st.com>, linux-iio@...r.kernel.org, 
	linux-stm32@...md-mailman.stormreply.com, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] iio: adc: stm32: add oversampling support

On Sat, Apr 12, 2025 at 4:26 PM Jonathan Cameron <jic23@...nel.org> wrote:
> On Thu, 10 Apr 2025 15:58:35 +0200
> Olivier Moysan <olivier.moysan@...s.st.com> wrote:

...

> > The current support of the oversampling feature aims at increasing
> > the data SNR, without changing the data resolution.
> > As the oversampling by itself increases data resolution,
> > a right shift is applied to keep initial resolution.
> > Only the oversampling ratio corresponding to a power of two are
> > supported here, to get a direct link between right shift and
> > oversampling ratio. (2exp(n) ratio <=> n right shift)

I have just noticed the interesting (and perhaps misleading) symbols
in formulas here and in the comment in the code.

I would expect to see the above as 2^n. Because exp makes me think
about e (natural logarithm base) rather than about power.

-- 
With Best Regards,
Andy Shevchenko