linux-kernel - Re: [PATCH v10 1/3] ARM: uncompress: Add be32tocpu macro

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Message-ID: <25r4pns0-srrp-nq3s-q4p5-11s925rq9sr0@syhkavp.arg>
Date:   Thu, 3 Dec 2020 11:26:03 -0500 (EST)
From:   Nicolas Pitre <nico@...xnic.net>
To:     Geert Uytterhoeven <geert+renesas@...der.be>
cc:     Russell King <linux@...linux.org.uk>,
        Ard Biesheuvel <ardb@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Dmitry Osipenko <digetx@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Arnd Bergmann <arnd@...db.de>,
        Eric Miao <eric.miao@...dia.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Lukasz Stelmach <l.stelmach@...sung.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Chris Brandt <chris.brandt@...esas.com>,
        linux-arm-kernel@...ts.infradead.org,
        linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 1/3] ARM: uncompress: Add be32tocpu macro

On Thu, 3 Dec 2020, Geert Uytterhoeven wrote:

> DTB stores all values as 32-bit big-endian integers.
> Add a macro to convert such values to native CPU endianness, to reduce
> duplication.
> 
> Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>

I agree with Ard's suggestions. In any case:

Reviewed-by: Nicolas Pitre <nico@...xnic.net>

> ---
> v10:
>   - New.
> ---
>  arch/arm/boot/compressed/head.S | 26 ++++++++++++--------------
>  1 file changed, 12 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
> index 835ce64f1674c9a2..aabdc544c03aafdc 100644
> --- a/arch/arm/boot/compressed/head.S
> +++ b/arch/arm/boot/compressed/head.S
> @@ -165,6 +165,16 @@
>  		orr	\res, \res, \tmp1, lsl #24
>  		.endm
>  
> +		.macro	be32tocpu, val, tmp
> +#ifndef __ARMEB__
> +		/* convert to little endian */
> +		eor	\tmp, \val, \val, ror #16
> +		bic	\tmp, \tmp, #0x00ff0000
> +		mov	\val, \val, ror #8
> +		eor	\val, \val, \tmp, lsr #8
> +#endif
> +		.endm
> +
>  		.section ".start", "ax"
>  /*
>   * sort out different calling conventions
> @@ -345,13 +355,7 @@ restart:	adr	r0, LC1
>  
>  		/* Get the initial DTB size */
>  		ldr	r5, [r6, #4]
> -#ifndef __ARMEB__
> -		/* convert to little endian */
> -		eor	r1, r5, r5, ror #16
> -		bic	r1, r1, #0x00ff0000
> -		mov	r5, r5, ror #8
> -		eor	r5, r5, r1, lsr #8
> -#endif
> +		be32tocpu r5, r1
>  		dbgadtb	r6, r5
>  		/* 50% DTB growth should be good enough */
>  		add	r5, r5, r5, lsr #1
> @@ -403,13 +407,7 @@ restart:	adr	r0, LC1
>  
>  		/* Get the current DTB size */
>  		ldr	r5, [r6, #4]
> -#ifndef __ARMEB__
> -		/* convert r5 (dtb size) to little endian */
> -		eor	r1, r5, r5, ror #16
> -		bic	r1, r1, #0x00ff0000
> -		mov	r5, r5, ror #8
> -		eor	r5, r5, r1, lsr #8
> -#endif
> +		be32tocpu r5, r1
>  
>  		/* preserve 64-bit alignment */
>  		add	r5, r5, #7
> -- 
> 2.25.1
> 
>