linux-kernel - Re: [PATCH v3 10/27] staging: iio: resolver: ad2s1210: use regmap for config registers

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Date:   Sat, 30 Sep 2023 15:51:07 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     David Lechner <dlechner@...libre.com>
Cc:     linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-staging@...ts.linux.dev,
        David Lechner <david@...hnology.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Nuno Sá <nuno.sa@...log.com>,
        Axel Haslam <ahaslam@...libre.com>,
        Philip Molloy <pmolloy@...libre.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 10/27] staging: iio: resolver: ad2s1210: use regmap
 for config registers

On Fri, 29 Sep 2023 12:23:15 -0500
David Lechner <dlechner@...libre.com> wrote:

> From: David Lechner <david@...hnology.com>
> 
> From: David Lechner <dlechner@...libre.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@...libre.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