linux-kernel - Re: [PATCH] iio: adc: ad7124: add debugfs to disable single cycle mode

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Message-ID: <20250920120014.2c4b6701@jic23-huawei>
Date: Sat, 20 Sep 2025 12:00:14 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Nuno Sá <noname.nuno@...il.com>
Cc: David Lechner <dlechner@...libre.com>, Michael Hennerich 
 <Michael.Hennerich@...log.com>, Nuno Sá 
 <nuno.sa@...log.com>, Andy Shevchenko <andy@...nel.org>,
 linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: adc: ad7124: add debugfs to disable single cycle
 mode

On Thu, 18 Sep 2025 11:34:48 +0100
Nuno Sá <noname.nuno@...il.com> wrote:

> On Wed, 2025-09-17 at 18:03 -0500, David Lechner wrote:
> > Add a boolean debugfs attribute to allow disabling the SINGLE_CYCLE
> > bit in the FILTER registers.
> > 
> > This causes data to be read on every conversion instead of doing the
> > usual 3 or 4 conversions per sample (depending on the filter). This is
> > only needed for very specific use cases, such as validating the
> > performance of the ADC. So we just expose this feature through debugfs
> > for the rare cases where it is needed by people who really know what
> > they are doing.
> > 
> > Signed-off-by: David Lechner <dlechner@...libre.com>
> > ---
> > In a recent discussion with an engineer who has used these chips a lot,
> > we confirmed that we made the right choice in [1] about always enabling
> > the SINGLE_CYCLE bit. That is what is needed in normal operation and is
> > the expected behavior.
> > 
> > But there are some occasions where we might want to turn it off for
> > hardware debugging (e.g. to peer into what the filter on the ADC is
> > doing). Hence, this patch to add a debugfs entry to allow it.
> > 
> > FYI, there will be some trivial fuzz between this patch and the "iio:
> > adc: ad7124: change setup reg allocation strategy" patch, but I expect
> > changes to be requested on that one, so will likely work itself out
> > by the time it actually gets picked up.
> > 
> > [1]:
> > https://lore.kernel.org/linux-iio/20250910-iio-adc-ad7124-fix-samp-freq-for-multi-channel-v4-1-8ca624c6114c@baylibre.com/
> > ---  
> 
> Reviewed-by: Nuno Sá <nuno.sa@...log.com>
> 
Applied to the testing branch of iio.git.  Unless the merge window is delayed,
this will be material for next cycle now.

Thanks,

Jonathan