linux-kernel - Re: [RFC PATCH] Remove CONFIG_DCACHE_WORD

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Date:	Wed, 12 Mar 2014 07:37:20 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Joe Perches <joe@...ches.com>
Cc:	linux-arch <linux-arch@...r.kernel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Russell King <linux@....linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Alexander Viro <viro@...iv.linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
	Anton Blanchard <anton@....ibm.com>
Subject: Re: [RFC PATCH] Remove CONFIG_DCACHE_WORD_ACCESS

On Tue, 2014-03-04 at 12:23 -0800, Joe Perches wrote:
> It seems to duplicate CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
> so use that instead.
> 
> This changes the !CPU_LITTLE_ENDIAN powerpc arch to use unaligned
> accesses in fs/dcache.c and fs/namei.c as
> CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is enabled for that arch.
> 
> Remove the now unused DCACHE_WORD_ACCESS defines & uses.

Interesting.. we have word-at-a-time but we never enabled
DCACHE_WORD_ACCESS, I wonder why that is. In fact, we should
probably do it for LE as well for P8 if we can make a P8
only config option...

Anton, what do you reckon here ?

Cheers,
Ben.

> Signed-off-by: Joe Perches <joe@...ches.com>
> ---
>  arch/arm/Kconfig                      | 1 -
>  arch/arm/include/asm/word-at-a-time.h | 4 ++--
>  arch/arm64/Kconfig                    | 1 -
>  arch/x86/Kconfig                      | 1 -
>  fs/Kconfig                            | 4 ----
>  fs/dcache.c                           | 2 +-
>  fs/namei.c                            | 2 +-
>  7 files changed, 4 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> index 623a272..d5a2e60 100644
> --- a/arch/arm/Kconfig
> +++ b/arch/arm/Kconfig
> @@ -12,7 +12,6 @@ config ARM
>  	select BUILDTIME_EXTABLE_SORT if MMU
>  	select CLONE_BACKWARDS
>  	select CPU_PM if (SUSPEND || CPU_IDLE)
> -	select DCACHE_WORD_ACCESS if HAVE_EFFICIENT_UNALIGNED_ACCESS
>  	select GENERIC_ATOMIC64 if (CPU_V7M || CPU_V6 || !CPU_32v6K || !AEABI)
>  	select GENERIC_CLOCKEVENTS_BROADCAST if SMP
>  	select GENERIC_IDLE_POLL_SETUP
> diff --git a/arch/arm/include/asm/word-at-a-time.h b/arch/arm/include/asm/word-at-a-time.h
> index a6d0a29..778b2ad 100644
> --- a/arch/arm/include/asm/word-at-a-time.h
> +++ b/arch/arm/include/asm/word-at-a-time.h
> @@ -54,7 +54,7 @@ static inline unsigned long find_zero(unsigned long mask)
>  #include <asm-generic/word-at-a-time.h>
>  #endif
>  
> -#ifdef CONFIG_DCACHE_WORD_ACCESS
> +#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
>  
>  /*
>   * Load an unaligned word from kernel space.
> @@ -94,5 +94,5 @@ static inline unsigned long load_unaligned_zeropad(const void *addr)
>  	return ret;
>  }
>  
> -#endif	/* DCACHE_WORD_ACCESS */
> +#endif	/* HAVE_EFFICIENT_UNALIGNED_ACCESS */
>  #endif /* __ASM_ARM_WORD_AT_A_TIME_H */
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 764d682..2d6978c 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -13,7 +13,6 @@ config ARM64
>  	select CLONE_BACKWARDS
>  	select COMMON_CLK
>  	select CPU_PM if (SUSPEND || CPU_IDLE)
> -	select DCACHE_WORD_ACCESS
>  	select GENERIC_CLOCKEVENTS
>  	select GENERIC_CLOCKEVENTS_BROADCAST if SMP
>  	select GENERIC_IOMAP
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index abb261e..60cfa073 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -98,7 +98,6 @@ config X86
>  	select CLKEVT_I8253
>  	select ARCH_HAVE_NMI_SAFE_CMPXCHG
>  	select GENERIC_IOMAP
> -	select DCACHE_WORD_ACCESS
>  	select GENERIC_SMP_IDLE_THREAD
>  	select ARCH_WANT_IPC_PARSE_VERSION if X86_32
>  	select HAVE_ARCH_SECCOMP_FILTER
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 312393f..7511271 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -4,10 +4,6 @@
>  
>  menu "File systems"
>  
> -# Use unaligned word dcache accesses
> -config DCACHE_WORD_ACCESS
> -       bool
> -
>  if BLOCK
>  
>  source "fs/ext2/Kconfig"
> diff --git a/fs/dcache.c b/fs/dcache.c
> index 265e0ce..4e3c195 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -163,7 +163,7 @@ int proc_nr_dentry(ctl_table *table, int write, void __user *buffer,
>   * Compare 2 name strings, return 0 if they match, otherwise non-zero.
>   * The strings are both count bytes long, and count is non-zero.
>   */
> -#ifdef CONFIG_DCACHE_WORD_ACCESS
> +#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
>  
>  #include <asm/word-at-a-time.h>
>  /*
> diff --git a/fs/namei.c b/fs/namei.c
> index 385f781..1ee33ca 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -1618,7 +1618,7 @@ static inline int nested_symlink(struct path *path, struct nameidata *nd)
>   *   the final mask". Again, that could be replaced with a
>   *   efficient population count instruction or similar.
>   */
> -#ifdef CONFIG_DCACHE_WORD_ACCESS
> +#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
>  
>  #include <asm/word-at-a-time.h>
>  
> 
> 
> --
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