linux-kernel - Re: [PATCH 4/6] regmap: Add the LZO cache support

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Date:	Mon, 05 Sep 2011 18:18:30 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Dimitris Papastamos <dp@...nsource.wolfsonmicro.com>
CC:	linux-kernel@...r.kernel.org,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	Liam Girdwood <lrg@...com>,
	Graeme Gregory <gg@...mlogic.co.uk>,
	Samuel Oritz <sameo@...ux.intel.com>
Subject: Re: [PATCH 4/6] regmap: Add the LZO cache support

On 09/05/2011 03:51 PM, Dimitris Papastamos wrote:
> This patch adds support for LZO compression when storing the register
> cache.
> 
> For a typical device whose register map would normally occupy 25kB or 50kB
> by using the LZO compression technique, one can get down to ~5-7kB.  There
> might be a performance penalty associated with each individual read/write
> due to decompressing/compressing the underlying cache, however that should not
> be noticeable.  These memory benefits depend on whether the target architecture
> can get rid of the memory occupied by the original register defaults cache
> which is marked as __devinitconst.  Nevertheless there will be some memory
> gain even if the target architecture can't get rid of the original register
> map, this should be around ~30-32kB instead of 50kB.
> 
> Signed-off-by: Dimitris Papastamos <dp@...nsource.wolfsonmicro.com>
> ---
>  drivers/base/regmap/Makefile       |    2 +-
>  drivers/base/regmap/internal.h     |    2 +
>  drivers/base/regmap/regcache-lzo.c |  361 ++++++++++++++++++++++++++++++++++++
>  drivers/base/regmap/regcache.c     |    1 +
>  include/linux/regmap.h             |    1 +
>  5 files changed, 366 insertions(+), 1 deletions(-)
>  create mode 100644 drivers/base/regmap/regcache-lzo.c
> 

Fails to compile due to CONFIG_LZO_{COMPRESS,DECOMPRESS} not being selected.
Also it will have issues, with caches where we don't use raw cache defaults.
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