Re: [PATCH v3 2/2] arm64: cacheinfo: Update cache_line_size detected from DT or PPTT

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, May 27, 2019 at 10:06:08AM +0800, Shaokun Zhang wrote:
> cache_line_size is derived from CTR_EL0.CWG field and is called mostly
> for I/O device drivers. For HiSilicon certain plantform, like the
> Kunpeng920 server SoC, cache line sizes are different between L1/2
> cache and L3 cache while L1 cache line size is 64-byte and L3 is 128-byte,
> but CTR_EL0.CWG is misreporting using L1 cache line size.
> 
> We shall correct the right value which is important for I/O performance.
> Let's update the cache line size if it is detected from DT or PPTT
> information.
> 
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Sudeep Holla <sudeep.holla@arm.com>
> Cc: Jeremy Linton <jeremy.linton@arm.com>
> Cc: Zhenfa Qiu <qiuzhenfa@hisilicon.com>
> Reported-by: Zhenfa Qiu <qiuzhenfa@hisilicon.com>
> Suggested-by: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
> ---
>  arch/arm64/include/asm/cache.h |  6 +-----
>  arch/arm64/kernel/cacheinfo.c  | 11 +++++++++++
>  2 files changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/cache.h b/arch/arm64/include/asm/cache.h
> index 926434f413fa..758af6340314 100644
> --- a/arch/arm64/include/asm/cache.h
> +++ b/arch/arm64/include/asm/cache.h
> @@ -91,11 +91,7 @@ static inline u32 cache_type_cwg(void)
>  
>  #define __read_mostly __attribute__((__section__(".data..read_mostly")))
>  
> -static inline int cache_line_size(void)
> -{
> -	u32 cwg = cache_type_cwg();
> -	return cwg ? 4 << cwg : ARCH_DMA_MINALIGN;
> -}
> +int cache_line_size(void);
>  
>  /*
>   * Read the effective value of CTR_EL0.
> diff --git a/arch/arm64/kernel/cacheinfo.c b/arch/arm64/kernel/cacheinfo.c
> index 0bf0a835122f..3d54b0024246 100644
> --- a/arch/arm64/kernel/cacheinfo.c
> +++ b/arch/arm64/kernel/cacheinfo.c
> @@ -28,6 +28,17 @@
>  #define CLIDR_CTYPE(clidr, level)	\
>  	(((clidr) & CLIDR_CTYPE_MASK(level)) >> CLIDR_CTYPE_SHIFT(level))
>  
> +int cache_line_size(void)
> +{
> +	u32 cwg = cache_type_cwg();
> +
> +	if (coherency_max_size != 0)
> +		return coherency_max_size;

Ah, you use it here.

> +
> +	return cwg ? 4 << cwg : ARCH_DMA_MINALIGN;

Shouldn't you set the variable if it is 0 here as well?

> +}
> +EXPORT_SYMBOL(cache_line_size);

EXPORT_SYMBOL_GPL()?

thanks,

greg k-h

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