linux-kernel - Re: [PATCH 1/2] iio: adc: ad4695: add offload-based oversampling support

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Message-ID: <fe046df1-1868-4008-8999-97a9d0b90b58@baylibre.com>
Date: Mon, 23 Dec 2024 11:33:37 -0500
From: Trevor Gamblin <tgamblin@...libre.com>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Michael Hennerich <michael.hennerich@...log.com>,
 Nuno Sá <nuno.sa@...log.com>,
 David Lechner <dlechner@...libre.com>, Lars-Peter Clausen <lars@...afoo.de>,
 Jonathan Corbet <corbet@....net>, linux-iio@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH 1/2] iio: adc: ad4695: add offload-based oversampling
 support


On 2024-12-19 11:13, Jonathan Cameron wrote:
> On Tue, 17 Dec 2024 16:47:28 -0500
> Trevor Gamblin <tgamblin@...libre.com> wrote:
>
>> Add support for the ad4695's oversampling feature when SPI offload is
>> available. This allows the ad4695 to set oversampling ratios on a
>> per-channel basis, raising the effective-number-of-bits from 16
>> (OSR == 1) to 17 (4), 18 (16), or 19 (64) for a given sample (i.e. one
>> full cycle through the auto-sequencer). The logic for reading and
>> writing sampling frequency for a given channel is also adjusted based on
>> the current oversampling ratio.
>>
>> The non-offload case isn't supported as there isn't a good way to
>> trigger the CNV pin in this mode. Support could be added in the future
>> if a use-case arises.
>>
>> Signed-off-by: Trevor Gamblin <tgamblin@...libre.com>
> Hi Trevor,
>
> The clamping fun of get_calibbias seems overkill. If this isn't going to ever
> overflow an s64 maybe just use the high precision to do it the easy way.
> I'm not sure you can't just fit it in an s32 for that matter. I've just
> not done the maths to check.

Hi Jonathan,

Thanks for your feedback. I'll look it over again, do some testing, and 
see if it can be simplified.

Trevor