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SubjectRe: [PATCH 1/2] ARCv2: Enable unaligned access in early ASM code
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On Tue, 2019-01-29 at 09:21 -0800, Vineet Gupta wrote:
> On 1/16/19 3:29 AM, Eugeniy Paltsev wrote:
> > Even though we do enable AD bit in arc_init_IRQ() we need to do
> > it in early ASM code otherwise we may face unaligned data until
> > we reach arc_init_IRQ() because GCC starting from v8.1.0 actively
> > generates unaligned data as it assumes that:
> > * ARCv2 always has support of unaliged data
> > * This support is turned on in runtime
> >
> > Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
> > ---
> > arch/arc/kernel/head.S | 10 ++++++++++
> > 1 file changed, 10 insertions(+)
> >
> > diff --git a/arch/arc/kernel/head.S b/arch/arc/kernel/head.S
> > index 8b90d25a15cc..d5b7a572365a 100644
> > --- a/arch/arc/kernel/head.S
> > +++ b/arch/arc/kernel/head.S
> > @@ -17,6 +17,9 @@
> > #include <asm/entry.h>
> > #include <asm/arcregs.h>
> > #include <asm/cache.h>
> > +#ifdef CONFIG_ISA_ARCV2
> > +#include <asm/irqflags-arcv2.h>
> > +#endif
>
> I presume there is no specific reason to include this conditionally.
> irqflags.h already includes the right version.

Agree.
I've just forgotten about common irqflags.h

Will fix in V2.

> >
> > .macro CPU_EARLY_SETUP
> >
> > @@ -47,6 +50,13 @@
> > sr r5, [ARC_REG_DC_CTRL]
> >
> > 1:
> > +
> > +#ifdef CONFIG_ISA_ARCV2
> > + ; Enable handling of unaligned access in the CPU as by default
> > + ; this HW feature is disabled while GCC starting from 8.1.0
> > + ; unconditionally uses it for ARC HS cores.
> > + flag 1 << STATUS_AD_BIT
> > +#endif
> > .endm
> >
> > .section .init.text, "ax",@progbits
> >
>
>
--
Eugeniy Paltsev
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