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

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Message-ID: <20110822190838.3e03c3ec@debxo>
Date:	Mon, 22 Aug 2011 19:08:38 -0700
From:	Andres Salomon <dilinger@...ued.net>
To:	Eric Miao <eric.y.miao@...il.com>
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, 23 Aug 2011 08:07:41 +0800
Eric Miao <eric.y.miao@...il.com> wrote:

> 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.
> 

I guess I don't follow.  I think you're talking about adding it to the
standard_io_desc array, but that would require having it pre-mapped and
knowing the virtual address.  Or were you planning to ioremap it?
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