From mboxrd@z Thu Jan 1 00:00:00 1970 From: u.kleine-koenig@pengutronix.de (Uwe =?iso-8859-1?Q?Kleine-K=F6nig?=) Date: Fri, 15 Oct 2010 16:23:10 +0200 Subject: [PATCH .36-rc8] arm: mm: allow, but warn, when issuing ioremap() on RAM In-Reply-To: <1287152120-7201-1-git-send-email-felipe.contreras@gmail.com> References: <1287152120-7201-1-git-send-email-felipe.contreras@gmail.com> Message-ID: <20101015142310.GD16893@pengutronix.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Fri, Oct 15, 2010 at 05:15:20PM +0300, Felipe Contreras wrote: > From: Catalin Marinas > > 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-K?nig > Cc: Russell King > Cc: Andrew Morton > Cc: Richard Woodruff > Signed-off-by: Catalin Marinas > Signed-off-by: Felipe Contreras > --- > 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) > -- > 1.7.3.1.2.g7fe2b > > -- Pengutronix e.K. | Uwe Kleine-K?nig | Industrial Linux Solutions | http://www.pengutronix.de/ |