[PATCH] Skip unnecessary pte makeup when clearing it.

[u.kleine-koenig@pengutronix.de (Uwe Kleine-König)]

On Mon, Jan 30, 2012 at 09:47:51AM +0800, bill4carson at gmail.com wrote:
> From: Bill Carson <bill4carson@gmail.com>
> 
> If we are only about to clear a hardware pte entry, then pte makeup code is
> unnecessary for cpu_v7_set_pte_ext and armv6_set_pte_ext, so just skip it.
> 
> Signed-off-by: Bill Carson <bill4carson@gmail.com>
> ---
>  arch/arm/mm/proc-macros.S    |   10 +++++-----
>  arch/arm/mm/proc-v7-2level.S |   10 +++++-----
>  2 files changed, 10 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm/mm/proc-macros.S b/arch/arm/mm/proc-macros.S
> index 2d8ff3a..907b524 100644
> --- a/arch/arm/mm/proc-macros.S
> +++ b/arch/arm/mm/proc-macros.S
> @@ -138,6 +138,10 @@
>  	.macro	armv6_set_pte_ext pfx
>  	str	r1, [r0], #2048			@ linux version
>  
> +	tst	r1, #L_PTE_YOUNG
> +	tstne	r1, #L_PTE_PRESENT
> +	moveq	r3, #0
> +	beq	1f
>  	bic	r3, r1, #0x000003fc
>  	bic	r3, r3, #PTE_TYPE_MASK
>  	orr	r3, r3, r2
> @@ -163,11 +167,7 @@
>  	orrne	r3, r3, #PTE_EXT_XN
>  
>  	orr	r3, r3, r2
> -
> -	tst	r1, #L_PTE_YOUNG
> -	tstne	r1, #L_PTE_PRESENT
> -	moveq	r3, #0
> -
> +1:
>  	str	r3, [r0]
>  	mcr	p15, 0, r0, c7, c10, 1		@ flush_pte
>  	.endm
> diff --git a/arch/arm/mm/proc-v7-2level.S b/arch/arm/mm/proc-v7-2level.S
> index 3a4b3e7..869bebc 100644
> --- a/arch/arm/mm/proc-v7-2level.S
> +++ b/arch/arm/mm/proc-v7-2level.S
> @@ -76,6 +76,10 @@ ENTRY(cpu_v7_set_pte_ext)
>  #ifdef CONFIG_MMU
>  	str	r1, [r0]			@ linux version
>  
> +	tst	r1, #L_PTE_YOUNG
> +	tstne	r1, #L_PTE_PRESENT
> +	moveq	r3, #0
> +	beq		1f
This double tab looks wrong. Other than that I think the patch is OK.
Note I don't have a clue about ptes but your changes are a logical nop.

Best regards
Uwe

>  	bic	r3, r1, #0x000003f0
>  	bic	r3, r3, #PTE_TYPE_MASK
>  	orr	r3, r3, r2
> @@ -98,11 +102,7 @@ ENTRY(cpu_v7_set_pte_ext)
>  
>  	tst	r1, #L_PTE_XN
>  	orrne	r3, r3, #PTE_EXT_XN
> -
> -	tst	r1, #L_PTE_YOUNG
> -	tstne	r1, #L_PTE_PRESENT
> -	moveq	r3, #0
> -
> +1:
>   ARM(	str	r3, [r0, #2048]! )
>   THUMB(	add	r0, r0, #2048 )
>   THUMB(	str	r3, [r0] )

-- 
Pengutronix e.K.                           | Uwe Kleine-K?nig            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |