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From: Andre Przywara <andre.przywara@arm.com>
To: Mark Rutland <mark.rutland@arm.com>
Cc: linux-arm-kernel@lists.infradead.org, Jaxson.Han@arm.com,
	robin.murphy@arm.com, vladimir.murzin@arm.com, Wei.Chen@arm.com
Subject: Re: [bootwrapper PATCH v2 05/13] aarch64: add mov_64 macro
Date: Fri, 14 Jan 2022 15:50:32 +0000	[thread overview]
Message-ID: <20220114155032.2d5bab06@donnerap.cambridge.arm.com> (raw)
In-Reply-To: <20220114105653.3003399-6-mark.rutland@arm.com>

On Fri, 14 Jan 2022 10:56:45 +0000
Mark Rutland <mark.rutland@arm.com> wrote:

Hi Mark,

> In subsequent patches we'll need to load 64-bit values into GPRs before
> the CPU is in a known endianness, where we cannot use literal pools.
> 
> In preparation for that, this patch adds a new `mov_64` macro to load a
> 64-bit value into a GPR using a sequence of MOV and MOVKs, which will
> function the same regardless of the CPU's endianness.
> 
> At the same time, move the `cpuid` macro to use `mov_64` internally.
> 
> Signed-off-by: Mark Rutland <mark.rutland@arm.com>

Not sure that's worth it, but there is a simpler version of that TF-A
macro, along the lines of:

	.if ((\val) >> 16) & 0xffff
		movk    \dest, #(((\val) >> 16) & 0xffff), lsl #16
	.endif

It's a bit less optimal in a corner case than the TF-A version, but avoids
the few pointless " movk x0, #0x0, lsl #..." I found in the code.

But that's an optimisation detail, so anyway:

Reviewed-by: Andre Przywara <andre.przywara@arm.com>

Cheers,
Andre

> ---
>  arch/aarch64/common.S | 10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/aarch64/common.S b/arch/aarch64/common.S
> index c7171a9..3279fa9 100644
> --- a/arch/aarch64/common.S
> +++ b/arch/aarch64/common.S
> @@ -9,9 +9,17 @@
>  
>  #include <cpu.h>
>  
> +	/* Load a 64-bit value using immediates */
> +	.macro	mov_64 dest, val
> +	mov	\dest, #(((\val) >>  0) & 0xffff)
> +	movk	\dest, #(((\val) >> 16) & 0xffff), lsl #16
> +	movk	\dest, #(((\val) >> 32) & 0xffff), lsl #32
> +	movk	\dest, #(((\val) >> 48) & 0xffff), lsl #48
> +	.endm
> +
>  	/* Put MPIDR into \dest, clobber \tmp and flags */
>  	.macro cpuid dest, tmp
>  	mrs	\dest, mpidr_el1
> -	ldr	\tmp, =MPIDR_ID_BITS
> +	mov_64	\tmp, MPIDR_ID_BITS
>  	ands	\dest, \dest, \tmp
>  	.endm


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  reply	other threads:[~2022-01-14 15:52 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-14 10:56 [bootwrapper PATCH v2 00/13] Cleanups and improvements Mark Rutland
2022-01-14 10:56 ` [bootwrapper PATCH v2 01/13] Document entry requirements Mark Rutland
2022-01-14 10:56 ` [bootwrapper PATCH v2 02/13] Add bit-field macros Mark Rutland
2022-01-17 12:11   ` Steven Price
2022-01-17 13:28     ` Mark Rutland
2022-01-14 10:56 ` [bootwrapper PATCH v2 03/13] aarch64: add system register accessors Mark Rutland
2022-01-14 15:32   ` Andre Przywara
2022-01-14 10:56 ` [bootwrapper PATCH v2 04/13] aarch32: add coprocessor accessors Mark Rutland
2022-01-14 10:56 ` [bootwrapper PATCH v2 05/13] aarch64: add mov_64 macro Mark Rutland
2022-01-14 15:50   ` Andre Przywara [this message]
2022-01-14 10:56 ` [bootwrapper PATCH v2 06/13] aarch64: initialize SCTLR_ELx for the boot-wrapper Mark Rutland
2022-01-14 18:12   ` Andre Przywara
2022-01-17 12:15     ` Mark Rutland
2022-01-17 13:05       ` Mark Rutland
2022-01-18 12:37         ` Andre Przywara
2022-01-25 13:32           ` Mark Rutland
2022-01-19 12:42       ` Mark Rutland
2022-01-14 10:56 ` [bootwrapper PATCH v2 07/13] Rework common init C code Mark Rutland
2022-01-17 16:23   ` Andre Przywara
2022-01-14 10:56 ` [bootwrapper PATCH v2 08/13] Announce boot-wrapper mode / exception level Mark Rutland
2022-01-17 14:39   ` Andre Przywara
2022-01-17 15:50     ` Mark Rutland
2022-01-14 10:56 ` [bootwrapper PATCH v2 09/13] aarch64: move the bulk of EL3 initialization to C Mark Rutland
2022-01-17 14:31   ` Andre Przywara
2022-01-17 18:08     ` Mark Rutland
2022-01-17 18:31       ` Andre Przywara
2022-01-18 16:50         ` Mark Brown
2022-01-19 15:22           ` Mark Rutland
2022-01-14 10:56 ` [bootwrapper PATCH v2 10/13] aarch32: move the bulk of Secure PL1 " Mark Rutland
2022-01-17 14:52   ` Andre Przywara
2022-01-14 10:56 ` [bootwrapper PATCH v2 11/13] Announce locations of memory objects Mark Rutland
2022-01-14 15:30   ` Andre Przywara
2022-01-14 16:04     ` Robin Murphy
2022-01-14 16:30       ` Mark Rutland
2022-01-14 16:21     ` Mark Rutland
2022-01-17 14:59   ` Andre Przywara
2022-01-14 10:56 ` [bootwrapper PATCH v2 12/13] Rework bootmethod initialization Mark Rutland
2022-01-17 17:43   ` Andre Przywara
2022-01-25 14:00     ` Mark Rutland
2022-01-14 10:56 ` [bootwrapper PATCH v2 13/13] Unify start_el3 & start_no_el3 Mark Rutland
2022-01-17 17:43   ` Andre Przywara
2022-01-14 15:09 ` [bootwrapper PATCH v2 00/13] Cleanups and improvements Andre Przywara
2022-01-14 15:23   ` Mark Rutland

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