[PATCH 5/6] arm64: Implement pmem API support

[Catalin Marinas]

Two minor comments below.

On Tue, Jul 25, 2017 at 11:55:42AM +0100, Robin Murphy wrote:
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -960,6 +960,17 @@ config ARM64_UAO
>  	  regular load/store instructions if the cpu does not implement the
>  	  feature.
>  
> +config ARM64_PMEM
> +	bool "Enable support for persistent memory"
> +	select ARCH_HAS_PMEM_API
> +	help
> +	  Say Y to enable support for the persistent memory API based on the
> +	  ARMv8.2 DCPoP feature.
> +
> +	  The feature is detected at runtime, and the kernel will use DC CVAC
> +	  operations if DC CVAP is not supported (following the behaviour of
> +	  DC CVAP itself if the system does not define a point of persistence).

Any reason not to have this default y?

> --- a/arch/arm64/mm/cache.S
> +++ b/arch/arm64/mm/cache.S
> @@ -172,6 +172,20 @@ ENDPIPROC(__clean_dcache_area_poc)
>  ENDPROC(__dma_clean_area)
>  
>  /*
> + *	__clean_dcache_area_pop(kaddr, size)
> + *
> + * 	Ensure that any D-cache lines for the interval [kaddr, kaddr+size)
> + * 	are cleaned to the PoP.
> + *
> + *	- kaddr   - kernel address
> + *	- size    - size in question
> + */
> +ENTRY(__clean_dcache_area_pop)
> +	dcache_by_line_op cvap, sy, x0, x1, x2, x3
> +	ret
> +ENDPIPROC(__clean_dcache_area_pop)
> +
> +/*
>   *	__dma_flush_area(start, size)
>   *
>   *	clean & invalidate D / U line
> diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c
> index a682a0a2a0fa..a461a00ceb3e 100644
> --- a/arch/arm64/mm/pageattr.c
> +++ b/arch/arm64/mm/pageattr.c
> @@ -183,3 +183,21 @@ bool kernel_page_present(struct page *page)
>  }
>  #endif /* CONFIG_HIBERNATION */
>  #endif /* CONFIG_DEBUG_PAGEALLOC */
> +
> +#ifdef CONFIG_ARCH_HAS_PMEM_API
> +#include <asm/cacheflush.h>
> +
> +static inline void arch_wb_cache_pmem(void *addr, size_t size)
> +{
> +	/* Ensure order against any prior non-cacheable writes */
> +	dmb(sy);
> +	__clean_dcache_area_pop(addr, size);
> +}

Could we keep the dmb() in the actual __clean_dcache_area_pop()
implementation?

I can do the changes myself if you don't have any objections.

-- 
Catalin