From: Arnd Bergmann <arnd@arndb.de>
To: Bastian Hecht <hechtb@gmail.com>
Subject: Re: [PATCH 03/21] ARM: shmobile: don't call irqchip_init unconditionallyA
Date: Mon, 29 Apr 2013 14:58:16 +0200
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Cc: Simon Horman <horms@verge.net.au>,
        "linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
        linux-kernel@vger.kernel.org, Bastian Hecht <hechtb+renesas@gmail.com>,
        Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
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On Friday 26 April 2013, Bastian Hecht wrote:
> > This one seems broken as the armadillo800eva board currently uses
> > it to initialise GIC even if CONFIG_ATAGS is not defined.
> >
> > I did test the above change on the armadillo800eva board
> > with the above change and CONFIG_ATAGS disabled, the result was
> > a boot failure. With the change reverted booting seems fine.
> 
> CONFIG_ATAGS and CONFIG_ARM_APPENDED_DTB are two ways to pass the
> device tree information, right?

No, the two are methods alternative methods for booting from a legacy
boot loader. CONFIG_ATAGS is the old boot method without a DT, using
a board file and a MACHINE_START() macro. ARM_APPENDED_DTB means you
have a DT linked into the kernel but pass ATAGS to the kernel which
uses the passed data to modify the DT.

> So we run into trouble when we use the later but disable the first.
> Is there a reason why you wanted to avoid using two times just "if
> (!IS_ENABLED(CONFIG_OF))", Arnd?

I incorrectly assumed that the second one was only used without DT,
since it uses hardcoded MMIO locations rather than using of_iomap().

	Arnd
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