[PATCH .36-rc8] arm: mm: allow, but warn, when issuing ioremap() on RAM
u.kleine-koenig at pengutronix.de
Fri Oct 15 10:23:10 EDT 2010
On Fri, Oct 15, 2010 at 05:15:20PM +0300, Felipe Contreras wrote:
> From: Catalin Marinas <catalin.marinas at arm.com>
> Drivers have been relying on this behavior, but done so wrongly.
> However, rather than breaking drivers from .35 to .36, we should warn on
> .36 and only break on .37. This way we give a chance for contributors to
> fix the issues.
> According to ARM, the behavior of having multiple mappings is
> unspecified from ARMv6+. This causes real issues specially on modern
> hardware, and specially with speculative prefetching. So drivers need to
> be fixed.
> Also, since current hardware has palliative meassures to deal with
> multiple mappings with the same memory type but diferent cacheability
> attributes, ensure that such restriction is taking place.
> Cc: Uwe Kleine-König <u.kleine-koenig at pengutronix.de>
> Cc: Russell King <linux at arm.linux.org.uk>
> Cc: Andrew Morton <akpm at linux-foundation.org>
> Cc: Richard Woodruff <r-woodruff2 at ti.com>
> Signed-off-by: Catalin Marinas <catalin.marinas at arm.com>
> Signed-off-by: Felipe Contreras <felipe.contreras at gmail.com>
> arch/arm/mm/ioremap.c | 8 ++++++--
> 1 files changed, 6 insertions(+), 2 deletions(-)
> diff --git a/arch/arm/mm/ioremap.c b/arch/arm/mm/ioremap.c
> index ab50627..7dfd6dd 100644
> --- a/arch/arm/mm/ioremap.c
> +++ b/arch/arm/mm/ioremap.c
> @@ -202,10 +202,14 @@ void __iomem * __arm_ioremap_pfn_caller(unsigned long pfn,
> return NULL;
> - * Don't allow RAM to be mapped - this causes problems with ARMv6+
> + * This causes problems with ARMv6+. Will be disallowed soon.
s/soon/for 2.6.37/ ?
> + * Also avoid a second mapping with different shareability, which is
> + * not supposed to work anyway.
> if (WARN_ON(pfn_valid(pfn)))
> - return NULL;
> + if (__LINUX_ARM_ARCH__ >= 6 &&
> + (mtype != MT_DEVICE_CACHED && mtype != MT_DEVICE_WC))
> + mtype = MT_DEVICE_WC;
> type = get_mem_type(mtype);
> if (!type)
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