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Date: Sat, 30 Sep 2023 15:51:07 +0100
From: Jonathan Cameron <jic23@kernel.org>
To: David Lechner <dlechner@baylibre.com>
Cc: linux-iio@vger.kernel.org, devicetree@vger.kernel.org,
 linux-staging@lists.linux.dev, David Lechner <david@lechnology.com>, Rob
 Herring <robh+dt@kernel.org>, Krzysztof Kozlowski
 <krzysztof.kozlowski+dt@linaro.org>, Conor Dooley <conor+dt@kernel.org>,
 Michael Hennerich <Michael.Hennerich@analog.com>, Nuno =?UTF-8?B?U8Oh?=
 <nuno.sa@analog.com>, Axel Haslam <ahaslam@baylibre.com>, Philip Molloy
 <pmolloy@baylibre.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 10/27] staging: iio: resolver: ad2s1210: use regmap
 for config registers
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In-Reply-To: <20230929-ad2s1210-mainline-v3-10-fa4364281745@baylibre.com>
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	<20230929-ad2s1210-mainline-v3-10-fa4364281745@baylibre.com>
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On Fri, 29 Sep 2023 12:23:15 -0500
David Lechner <dlechner@baylibre.com> wrote:

> From: David Lechner <david@lechnology.com>
> 
> From: David Lechner <dlechner@baylibre.com>
> 
> This makes use of the regmap API to read and write the configuration
> registers. This simplifies code quite a bit and makes it safer
> (previously, it was easy to write a bad value to the config registers
> which causes the chip to lock up and need to be reset).
> 
> This chip has multiple modes of operation. In normal mode, we do not use
> regmap since there is no addressing - data is just bitshifted out during
> the SPI read. In config mode, we use regmap since it requires writing
> the address (with read/write flag) before reading and writing.
> 
> We don't use the lock provided by the regmap because we need to also
> synchronize with the normal mode SPI reads and with the various GPIOs.
> 
> There is also a quirk when reading registers (other than the fault
> register). If the address/data bit is set in the value read, then it
> indicates there is a configuration parity error and the data is not
> valid. Previously, this was checked in a few places, but not
> consistently. Now, we always check it in the regmap read function.
> 
> Signed-off-by: David Lechner <dlechner@baylibre.com>

This was a complex change, so I'm partly relying on the fact it clearly
works after the change to be sure it is correct ;)

Anyhow, code is much cleaner and probably right, so applied to the
togreg branch of iio.git and pushed out as testing for all the normal
reasons.

Thanks,

Jonathan