linux-kernel - Re: [PATCH] regmap: allow to define reg_update

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Message-ID: <YYPzN98RdHGEkK+n@sirena.org.uk>
Date:   Thu, 4 Nov 2021 14:50:31 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Ansuel Smith <ansuelsmth@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] regmap: allow to define reg_update_bits for no bus
 configuration

On Wed, Nov 03, 2021 at 10:53:17PM +0100, Ansuel Smith wrote:
> On Wed, Nov 03, 2021 at 09:29:11PM +0000, Mark Brown wrote:

> > > > I don't understand this change.  The point of the check for volatile
> > > > there is that if the register isn't volatile then we need to ensure that
> > > > the cache gets updated with any change that happens so we need to go
> > > > through paths that include cache updates.  The presence or otherwise of
> > > > a bus does not seem at all relevant here.

> I think I'm missing something. The user case is a driver that
> have CACHE DISABLED. The !map->bus check is added just to limit this to
> a no bus configuration not to permit this with CACHE enabled. The limit
> I was referring was in the init function where the update_bits is
> assigned to the map. I honestly didn't notice that anything with cache
> disabled was flagged as volatile.

In what way would the presence or absence of a bus be relevant to a
decision about being able to safely use an _update_bits() operation?

> So the rest of the changes permit to declare a update_bits function
> for a no bus configuration is good?

Probably, I'd need to look again.

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