linux-kernel - Re: [PATCH v2 05/25] powerpc/8xx: Fix vaddr for IMMR early remap

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Message-ID: <20150928233900.GB6161@home.buserror.net>
Date:	Mon, 28 Sep 2015 18:39:00 -0500
From:	Scott Wood <scottwood@...escale.com>
To:	Christophe Leroy <christophe.leroy@....fr>
CC:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	<linux-kernel@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH v2 05/25] powerpc/8xx: Fix vaddr for IMMR early remap

On Tue, Sep 22, 2015 at 06:50:38PM +0200, Christophe Leroy wrote:
> Memory: 124428K/131072K available (3748K kernel code, 188K rwdata,
> 648K rodata, 508K init, 290K bss, 6644K reserved)
> Kernel virtual memory layout:
>   * 0xfffdf000..0xfffff000  : fixmap
>   * 0xfde00000..0xfe000000  : consistent mem
>   * 0xfddf6000..0xfde00000  : early ioremap
>   * 0xc9000000..0xfddf6000  : vmalloc & ioremap
> SLUB: HWalign=16, Order=0-3, MinObjects=0, CPUs=1, Nodes=1
> 
> Mapping IMMR 1:1 is just wrong because it may overlap with another
> area. On most mpc8xx boards it is OK because IMMR is set to
> 0xff000000 but for instance on EP88xC board, IMMR is at 0xfa200000
> which overlaps with VM ioremap area
> 
> This patch fixes the virtual address for remapping IMMR to 0xff000000,
> regardless of the value of IMMR.
> 
> The size of IMMR area is 256kbytes (CPM at offset 0, security engine
> at offset 128) so 512kbytes is enough and allows to handle the EP88xC
> case (which is not 8Mbytes but only 2Mbytes aligned) the same way.
> 
> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>

Instead of hardcoding 0xff000000, can you use asm/fixmap.h to allocate a
virtual address at compile time?

-Scott
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