linux-kernel - Re: [PATCHv4 07/12] arm64: Simplify NR_FIX

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Date:	Fri, 16 Oct 2015 19:50:48 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	"Suzuki K. Poulose" <suzuki.poulose@....com>
Cc:	linux-arm-kernel@...ts.infradead.org, catalin.marinas@....com,
	marc.zyngier@....com, will.deacon@....com,
	linux-kernel@...r.kernel.org, ard.biesheuvel@...aro.org,
	chirstoff.dall@...aro.org, steve.capper@...aro.org,
	jeremy.linton@....com
Subject: Re: [PATCHv4 07/12] arm64: Simplify NR_FIX_BTMAPS calculation

On Fri, Oct 16, 2015 at 06:06:16PM +0100, Suzuki K. Poulose wrote:
> From: Mark Rutland <mark.rutland@....com>
> 
> Since NR_FIX_BTMAPS based on the fixed size of 256K, lets use
> a formula to derive it for a given page size, rather than defining
> for each page size.

No need to respin, but I'd prefer the wording:

----
We choose NR_FIX_BTMAPS such that each slot (NR_FIX_BTMAPS * PAGE_SIZE)
can address 256K.

Use division to derive NR_FIX_BTMAPS rather than defining it for each
page size.
----

Thanks for spinning this into a patch!

Mark.

> 
> Signed-off-by:  Mark Rutland <mark.rutland@....com>
> Signed-off-by:  Suzuki K. Poulose <suzuki.poulose@....com>
> ---
>  arch/arm64/include/asm/fixmap.h |    7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/fixmap.h b/arch/arm64/include/asm/fixmap.h
> index 8b9884c..3097045 100644
> --- a/arch/arm64/include/asm/fixmap.h
> +++ b/arch/arm64/include/asm/fixmap.h
> @@ -17,6 +17,7 @@
>  
>  #ifndef __ASSEMBLY__
>  #include <linux/kernel.h>
> +#include <linux/sizes.h>
>  #include <asm/boot.h>
>  #include <asm/page.h>
>  
> @@ -55,11 +56,7 @@ enum fixed_addresses {
>  	 * Temporary boot-time mappings, used by early_ioremap(),
>  	 * before ioremap() is functional.
>  	 */
> -#ifdef CONFIG_ARM64_64K_PAGES
> -#define NR_FIX_BTMAPS		4
> -#else
> -#define NR_FIX_BTMAPS		64
> -#endif
> +#define NR_FIX_BTMAPS		(SZ_256K / PAGE_SIZE)
>  #define FIX_BTMAPS_SLOTS	7
>  #define TOTAL_FIX_BTMAPS	(NR_FIX_BTMAPS * FIX_BTMAPS_SLOTS)
>  
> -- 
> 1.7.9.5
> 
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