linux-kernel - Re: [PATCH v5 1/8] regmap: Support atomic forced uncached reads

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Message-ID: <20210614103346.GB5646@sirena.org.uk>
Date:   Mon, 14 Jun 2021 11:33:46 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Sander Vanheule <sander@...nheule.net>
Cc:     Pavel Machek <pavel@....cz>, Rob Herring <robh+dt@...nel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J . Wysocki" <rafael@...nel.org>,
        Michael Walle <michael@...le.cc>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
        linux-gpio@...r.kernel.org, Andrew Lunn <andrew@...n.ch>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/8] regmap: Support atomic forced uncached reads

On Sat, Jun 12, 2021 at 11:12:31PM +0200, Sander Vanheule wrote:

> When a user wants to read a single uncached register, cache bypassing
> can be enabled. However, this is not atomic unless an external lock is
> used for the regmap. When using regcache_cache_bypass, the original
> bypass state also cannot be restored.

> Add support to atomically read a single uncached value, bypassing any
> regmap cache.

The expectation here is that if there is a need to do this for some
reason the user can arrange to do this for itself - if something is
happening that makes a normally non-volatile register volatile then 
it probably needs higher level coordination.  What's the use case?

> +int regmap_read_bypassed(struct regmap *map, unsigned int reg, unsigned int *val)

Bypassed what?  I think Andy's naming suggestion was much better.

Please also keep to 80 columns if you can, I know the requirements got
relaxed a bit but no need to do it excessively.

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