From: Mark Brown <broonie@kernel.org>
To: Jorge Ramirez-Ortiz <jramirez@baylibre.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [RFC] regmap: allow volatile register writes with cached only read maps
Date: Fri, 11 May 2018 11:00:49 +0900 [thread overview]
Message-ID: <20180511020049.GD949@sirena.org.uk> (raw)
In-Reply-To: <65607fde-d0e9-0f08-3042-f6a58b760896@baylibre.com>
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On Wed, May 09, 2018 at 01:49:21PM +0200, Jorge Ramirez-Ortiz wrote:
> On 05/09/2018 10:39 AM, Mark Brown wrote:
> > I don't understand what voltile access means for write only devices.
> > Volatile means that we don't read the cache but go direct to the
> > hardware so if we can't read the hardware that's pretty redundant, a
> > volatile read that goes to the cache is just a default read.
> 1. only cached reads: (as a consequence every regmap write must succeed).
> 2. cached writes: do not access the hardware unless the value differs from
> what is in the cache already or (3) applies.
> 3. support for selectable volatile writes: those that will always access the
> device no matter what the cache holds.
We don't currently suppress writes except when regmap_update_bits()
notices that the modification was a noop. You probably want to be using
regmap_write_bits() here instead of regmap_update_bits(), that will
always do the write.
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next prev parent reply other threads:[~2018-05-11 2:01 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-08 22:06 [RFC] regmap: allow volatile register writes with cached only read maps Jorge Ramirez-Ortiz
2018-05-09 8:39 ` Mark Brown
2018-05-09 11:49 ` Jorge Ramirez-Ortiz
2018-05-11 2:00 ` Mark Brown [this message]
2018-05-11 10:29 ` Jorge Ramirez-Ortiz
2018-05-13 2:22 ` Mark Brown
2018-05-17 7:12 ` Jorge Ramirez-Ortiz
2018-05-17 17:04 ` Mark Brown
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