linux-kernel - Re: [PATCH] ARM: allow, but warn, when issuing ioremap() on RAM

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Date:	Thu, 14 Oct 2010 17:47:09 +0300
From:	Felipe Contreras <felipe.contreras@...il.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Greg KH <greg@...ah.com>,
	linux-main <linux-kernel@...r.kernel.org>,
	linux-arm <linux-arm-kernel@...ts.infradead.org>,
	Arnd Hannemann <arnd@...dnet.de>,
	Han Jonghun <jonghun79.han@...il.com>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>, Hemant Pedanekar <hemantp@...com>
Subject: Re: [PATCH] ARM: allow, but warn, when issuing ioremap() on RAM

On Mon, Oct 11, 2010 at 6:25 PM, Russell King - ARM Linux
<linux@....linux.org.uk> wrote:
> On Sun, Oct 10, 2010 at 04:52:36AM +0300, Felipe Contreras wrote:
>> At the time 'fixup' is called, 'meminfo' is empty; the tags haven't
>> been parsed. So my solution is to move the memblock_add() after
>> 'reserve', and pass 'meminfo' as an argument:
>
> Here's a different approach which will work.  This pushes ARM further
> towards using memblock for everything relating to memory init (although
> we still have the old membank stuff around.)
>
> The advantage with this is that memblock is now used as the basis for
> determining where memory is, setting up the maps, freeing memory into
> the pools, etc.
>
> What this also means is that this code in the ->reserve callback:
>
>        size = min(size, SZ_2M);
>        base = memblock_alloc(size, min(align, SZ_2M));
>        memblock_free(base, size);
>        memblock_remove(base, size);

Why align to SZ_2M both the start and end?

> will result in [base+size] being removed from the available memory,
> using highmem if available, if not from lowmem and removing it from
> the lowmem memory map - which is exactly the behaviour we want.

Makes sense to me.

>  arch/arm/mm/init.c |  160 +++++++++++++++++++++++++++++++++++-----------------
>  arch/arm/mm/mmu.c  |   43 ++++++++------
>  mm/memblock.c      |    4 +
>  3 files changed, 138 insertions(+), 69 deletions(-)

This works fine:
Tested-by: Felipe Contreras <felipe.contreras@...il.com>

-- 
Felipe Contreras
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