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SubjectRe: [PATCH 1/2] ARCv2: Enable unaligned access in early ASM code
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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.

>
> .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
>

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