linux-kernel - Re: [RFC 16/23] ASoC: omap: mcbsp, mcpdm, dmic: raw read and write endian fix

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Message-ID: <s5h1u2gw99g.wl%tiwai@suse.de>
Date:	Sat, 16 Nov 2013 18:23:39 +0100
From:	Takashi Iwai <tiwai@...e.de>
To:	Jarkko Nikula <jarkko.nikula@...mer.com>
Cc:	Taras Kondratiuk <taras.kondratiuk@...aro.org>,
	linux-omap@...r.kernel.org, linaro-networking@...aro.org,
	Victor Kamensky <victor.kamensky@...aro.org>,
	Peter Ujfalusi <peter.ujfalusi@...com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>,
	Jaroslav Kysela <perex@...ex.cz>, alsa-devel@...a-project.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC 16/23] ASoC: omap: mcbsp, mcpdm, dmic: raw read and write endian fix

At Sat, 16 Nov 2013 18:09:51 +0200,
Jarkko Nikula wrote:
> 
> On 11/16/2013 02:01 AM, Taras Kondratiuk wrote:
> > From: Victor Kamensky <victor.kamensky@...aro.org>
> > 
> > All OMAP IP blocks expect LE data, but CPU may operate in BE mode.
> > Need to use endian neutral functions to read/write h/w registers.
> > I.e instead of __raw_read[lw] and __raw_write[lw] functions code
> > need to use read[lw]_relaxed and write[lw]_relaxed functions.
> > If the first simply reads/writes register, the second will byteswap
> > it if host operates in BE mode.
> > 
> > Changes are trivial sed like replacement of __raw_xxx functions
> > with xxx_relaxed variant.
> > 
> > Signed-off-by: Victor Kamensky <victor.kamensky@...aro.org>
> > Signed-off-by: Taras Kondratiuk <taras.kondratiuk@...aro.org>
> > ---
> >  sound/soc/omap/mcbsp.c      |   12 ++++++------
> >  sound/soc/omap/omap-dmic.c  |    4 ++--
> >  sound/soc/omap/omap-mcpdm.c |    4 ++--
> >  3 files changed, 10 insertions(+), 10 deletions(-)
> > 
> Looks ok to me by looking at the _relaxed definitions in
> arch/arm/include/asm/io.h.
> 
> Acked-by: Jarkko Nikula <jarkko.nikula@...mer.com>
> 

What's the reason to use _relaxed version in all places?

I understand this patch is to fix the endianess, so this can be
applied as is, as long as the original code works.  But, still in
general, I wonder how the concurrency is guaranteed by this driver
code...


thanks,

Takashi
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