[PATCH] iommu/arm-smmu-v2: ThunderX(errata-23399) mis-extends 64bit registers

[Russell King - ARM Linux]

On Thu, Jul 30, 2015 at 08:54:04PM +0000, Chalamarla, Tirumalesh wrote:
> is some thing like this looks good
> 
> +#ifdef CONFIG_64BIT
> +#define smmu_writeq(reg64, addr)       writeq_relaxed((reg64), (addr))
> +#else
> +#define smmu_writeq(reg64, addr)                       \
> +               writel_relaxed(((reg64) >> 32), ((addr) + 4));  \
> +               writel_relaxed((reg64), (addr))

It's missing a #endif.

This also suffers from multiple argument evaluation, and it hides that
there's two expressions here - which makes future maintanence harder.

#define smmu_writeq(reg64, addr)					\
	do {								\
		u64 __val = (reg64);					\
		volatile void __iomem *__addr = (addr);			\
		writel_relaxed(__val >> 32, __addr + 4);		\
		writel_relaxed(__val, __addr);				\
	} while (0)

is longer but is much preferred as it won't suffer side effects from
stuff like:

	if (...)
		smmu_writeq(val++, addr);

-- 
FTTC broadband for 0.8mile line: currently at 10.5Mbps down 400kbps up
according to speedtest.net.