Re: [PATCH] ARM: mmp: map sram as MT_MEMORY rather than MT_DEVICE

Russell King - ARM Linux
2011-08-23T00:08:19Z

On Mon, Aug 22, 2011 at 04:47:40PM -0700, Andres Salomon 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@queued.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);

Not a good idea fiddling about under the covers like that. The reason
that MT_MEMORY is not in asm/io.h is to stop it being used like this -
MT_MEMORY etc are not meant for general purpose use.

It needs to be looked at properly rather than working behind the APIs,
and making my life a misery by doing so, preventing me from making
changes where necessary by this kind of back-door use.

I guess we need a new ioremap_xxx() variant to cope with this.