[U-Boot] [PATCH] arm: enable unaligned access on ARMv7

Albert ARIBAUD
2012-06-22T09:15:01Z

Hi Lucas,

On Tue, 05 Jun 2012 21:06:20 +0200, Lucas Stach <dev@lynxeye.de> wrote:
> Hi Stephen,
>
> Am Dienstag, den 05.06.2012, 12:42 -0600 schrieb Stephen Warren:
> > On 06/05/2012 11:47 AM, Lucas Stach wrote:
> > > Recent toolchains default to using the hardware feature for
> > > unaligned access on ARM v7, rather than doing the software
> > > fallback. According to ARM this is safe as all v7 implementations
> > > have to support this feature.
> > > (http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0471c/BABJFFAE.html)
> > >
> > > To avoid CPU hangs when doing unaligned memory access, we have to
> > > turn off alignment checking in our CPU initialisation code.
> > > (http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0491c/CIHCGCFD.html)
> >
> > Does this behavior change trickle down to Linux/... too, or would
> > an OS completely re-initialize this state, and hence not be
> > affected?
> >
>
> Linux in particular does reinitialize this state and I expect any
> reasonable OS to do so.

Then what is the point of enabling it on U-Boot? Does it fix some issue
whereby some mis-aligned piece of data cannot be properly aligned?

Amicalement,
--
Albert.