linux-kernel - Re: [PATCH] ARM: mmp: map sram as MT_MEMORY rather than MT

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Date:	Tue, 23 Aug 2011 08:07:41 +0800
From:	Eric Miao <eric.y.miao@...il.com>
To:	Andres Salomon <dilinger@...ued.net>
Cc:	Leo Yan <leoy@...vell.com>, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Russell King <linux@....linux.org.uk>,
	Haojian Zhuang <hzhuang1@...vell.com>,
	Jon Nettleton <jon.nettleton@...il.com>
Subject: Re: [PATCH] ARM: mmp: map sram as MT_MEMORY rather than MT_DEVICE

On Tue, Aug 23, 2011 at 7:47 AM, Andres Salomon <dilinger@...ued.net> wrote:
> The sram code allocates memory with ioremap, which assumes MT_DEVICE
> for memory protections.  This explodes when we map sram for power
> management purposes and then attempt to execute it (jump_to_lp_sram)
> on the OLPC XO-1.75.  Instead, we want to specify MT_MEMORY, which
> doesn't set the L_PTE_XN bit.
>
> Signed-off-by: Andres Salomon <dilinger@...ued.net>
> ---
>  arch/arm/mach-mmp/sram.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
>
> Eric, this patch is against the devel branch of your pxa tree.
>
> diff --git a/arch/arm/mach-mmp/sram.c b/arch/arm/mach-mmp/sram.c
> index 4304f95..ca4d3c1 100644
> --- a/arch/arm/mach-mmp/sram.c
> +++ b/arch/arm/mach-mmp/sram.c
> @@ -21,6 +21,7 @@
>  #include <linux/err.h>
>  #include <linux/slab.h>
>  #include <linux/genalloc.h>
> +#include <asm/mach/map.h>
>
>  #include <mach/sram.h>
>
> @@ -87,7 +88,8 @@ static int __devinit sram_probe(struct platform_device *pdev)
>
>        info->sram_phys   = (phys_addr_t)res->start;
>        info->sram_size   = resource_size(res);
> -       info->sram_virt   = ioremap(info->sram_phys, info->sram_size);
> +       info->sram_virt   = __arm_ioremap(info->sram_phys, info->sram_size,
> +                                         MT_MEMORY);

I doubt MT_MEMORY is intended for use with __arm_ioremap(). There could
be other way around to the L_PTE_XN bit.

One other way I'm actually thinking of is to add the SRAM mapping to
mmp_map_io(). The difference of SRAM offset/size may result the
separation of mmp_map_io() into {pxa168,pxa910,mmp2}_map_io()
if necessary.

>        info->pool_name   = kstrdup(pdata->pool_name, GFP_KERNEL);
>        info->granularity = pdata->granularity;
>
> --
> 1.7.2.5
>
>
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