From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Subject: Re: [PATCH v4 01/21] arm/acpi: Emulate io ports for arm
Date: Wed, 27 Jan 2016 12:52:45 +0000
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To: Shannon Zhao <zhaoshenglong@huawei.com>
Cc: ian.campbell@citrix.com, stefano.stabellini@eu.citrix.com, peter.huangpeng@huawei.com, xen-devel@lists.xen.org, julien.grall@citrix.com, stefano.stabellini@citrix.com, shannon.zhao@linaro.org
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On Sat, 23 Jan 2016, Shannon Zhao wrote:
> From: Shannon Zhao <shannon.zhao@linaro.org>
> 
> Add macros to emulate x86 style ports for arm. This avoids modification in
> common code for acpi. Here just print a warning on ARM.
> 
> Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
> ---
> V4: print warning
> ---
>  xen/include/asm-arm/arm64/io.h | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
> 
> diff --git a/xen/include/asm-arm/arm64/io.h b/xen/include/asm-arm/arm64/io.h
> index 37abc47..ec5815d 100644
> --- a/xen/include/asm-arm/arm64/io.h
> +++ b/xen/include/asm-arm/arm64/io.h
> @@ -20,6 +20,7 @@
>  #ifndef _ARM_ARM64_IO_H
>  #define _ARM_ARM64_IO_H
>  
> +#include <asm/system.h>
>  #include <asm/byteorder.h>
>  
>  /*
> @@ -109,4 +110,21 @@ static inline u64 __raw_readq(const volatile void __iomem *addr)
>  #define writel(v,c)             ({ __iowmb(); writel_relaxed((v),(c)); })
>  #define writeq(v,c)             ({ __iowmb(); writeq_relaxed((v),(c)); })
>  
> +/*
> + * Emulate x86 io ports for ARM.
> + */
> +static inline void __iomem * __armio(u64 addr)
> +{
> +    printk(XENLOG_G_WARNING "Can't access IO %lx\n", addr);
> +    return (void __iomem *)addr;
> +}
> +
> +#define inb(c) ( readb( __armio(c) ) )
> +#define inw(c) ( readw( __armio(c) ) )
> +#define inl(c) ( readl( __armio(c) ) )
> +
> +#define outb(v, c) ( writeb(v, __armio(c) ) )
> +#define outw(v, c) ( writew(v, __armio(c) ) )
> +#define outl(v, c) ( writel(v, __armio(c) ) )

This is better than before, but it would still end up causing a write to
happen on outb, outw and outl. I would define them in a way so that
only the warning gets printed when they are called and nothing else.