linux-kernel - Re: [PATCH] ARM: OMAP4: sleep: byteswap data for big-endian

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Message-ID: <CAGo_u6oKpRFnPAWaqr9NTNAJB+m56jiDgBUgvsiZpaQ-3SF2kw@mail.gmail.com>
Date:	Tue, 14 Jan 2014 11:56:17 -0600
From:	Nishanth Menon <nm@...com>
To:	Victor Kamensky <victor.kamensky@...aro.org>
Cc:	Taras Kondratiuk <taras.kondratiuk@...aro.org>,
	Tero Kristo <t-kristo@...com>,
	Patch Tracking <patches@...aro.org>,
	Linaro Networking <linaro-networking@...aro.org>,
	Linaro Kernel <linaro-kernel@...ts.linaro.org>,
	Tony Lindgren <tony@...mide.com>,
	Russell King <linux@....linux.org.uk>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARM: OMAP4: sleep: byteswap data for big-endian

On Tue, Jan 14, 2014 at 11:35 AM, Victor Kamensky
<victor.kamensky@...aro.org> wrote:
>
> When BE kernel is built Makefile does take of compiling code in BE
> mode. I.e all proper flags like -mbig-endian and -Wl,--be8 will be set.

Agreed, and I assume you cannot instead switch to LE mode when
entering assembly assuming LE?

The reason I ask this is - most of our development is NOT in BE mode.
we will continue to manipulate and add assembly - AM335x, DRA7/OMAP5
etc.. and obviously not every code change will indulge in ensuring
right markers will be in place.

by ensuring readl_relaxed handles the variations, you have ensured
that I dont need to care about drivers other than to ensure they use
_relaxed variants. in the case of assembly, this does not seem long
term manageable.

>
>> is the idea of BE build meant to deal with having a single BE kernel
>> build work for all platforms (including LE ones)?
>
> Sort of. The idea here to run BE image on OMAP4 chip, with
> kernel that would deals with LE periphery correctly, but ARM
> core run in BE with special kernel that compiled for BE case (i.e
> CONFIG_CPU_BIG_ENDIAN is set).

I still dont get the usecase - other than "hey, we do this coz we can
do it!".. I mean, yep, it sounds great and all.. but 4 years down the
line, is this still going to work? is this going to be interesting
careabout? or we are just maintaining additional code for a passing
fancy or proof-of-concept?

Regards,
Nishanth Menon
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