linux-kernel - Re: [PATCH 2/4] LoongArch: Add JUMP_LINK_ADDR macro implementation to avoid using la.abs

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Message-ID: <c54bc8ac-fcc2-1cd4-56bc-167b094aec45@loongson.cn>
Date:   Sat, 14 Jan 2023 14:40:28 +0800
From:   Jinyang He <hejinyang@...ngson.cn>
To:     Youling Tang <tangyouling@...ngson.cn>,
        Huacai Chen <chenhuacai@...nel.org>,
        Xi Ruoyao <xry111@...111.site>
Cc:     Xuerui Wang <kernel@...0n.name>, loongarch@...ts.linux.dev,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] LoongArch: Add JUMP_LINK_ADDR macro implementation to
 avoid using la.abs


On 2023-01-09 17:07, Youling Tang wrote:
> Add JUMP_LINK_ADDR macro implementation to avoid using la.abs.
>
> Signed-off-by: Youling Tang <tangyouling@...ngson.cn>
> ---
>   arch/loongarch/include/asm/stackframe.h |  8 ++++++++
>   arch/loongarch/kernel/head.S            | 10 ++++------
>   arch/loongarch/power/suspend_asm.S      |  5 ++---
>   3 files changed, 14 insertions(+), 9 deletions(-)
>
> diff --git a/arch/loongarch/include/asm/stackframe.h b/arch/loongarch/include/asm/stackframe.h
> index 96c94035b5d0..f538b3a6d680 100644
> --- a/arch/loongarch/include/asm/stackframe.h
> +++ b/arch/loongarch/include/asm/stackframe.h
> @@ -216,4 +216,12 @@
>   	RESTORE_SP_AND_RET \docfi
>   	.endm
>   
> +/* Jump to the virtual address of the link. */
> +	.macro JUMP_LINK_ADDR

Hi, Youling


IMHO the JUMP_CACHE_ADDR is more suitable. And it not clear higt bits,
although the result always true currently. Lastly, this macro clobbers
t0 and t1, I'd suggest pass them in as args.


Thanks,

Jinyang

> +	li.d	t0, CACHE_BASE
> +	pcaddi	t1, 0
> +	or	t0, t0, t1
> +	jirl	zero, t0, 0xc
> +	.endm
> +
>   #endif /* _ASM_STACKFRAME_H */
> diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
> index aa6181714ec3..e8a4bf9d7599 100644
> --- a/arch/loongarch/kernel/head.S
> +++ b/arch/loongarch/kernel/head.S
> @@ -52,9 +52,8 @@ SYM_CODE_START(kernel_entry)			# kernel entry point
>   
>   	/* We might not get launched at the address the kernel is linked to,
>   	   so we jump there.  */
> -	la.abs		t0, 0f
> -	jr		t0
> -0:
> +	JUMP_LINK_ADDR
> +
>   	/* Enable PG */
>   	li.w		t0, 0xb0		# PLV=0, IE=0, PG=1
>   	csrwr		t0, LOONGARCH_CSR_CRMD
> @@ -106,9 +105,8 @@ SYM_CODE_START(smpboot_entry)
>   	li.d		t0, CSR_DMW1_INIT	# CA, PLV0
>   	csrwr		t0, LOONGARCH_CSR_DMWIN1
>   
> -	la.abs		t0, 0f
> -	jr		t0
> -0:
> +	JUMP_LINK_ADDR
> +
>   	/* Enable PG */
>   	li.w		t0, 0xb0		# PLV=0, IE=0, PG=1
>   	csrwr		t0, LOONGARCH_CSR_CRMD
> diff --git a/arch/loongarch/power/suspend_asm.S b/arch/loongarch/power/suspend_asm.S
> index eb2675642f9f..596a682a7924 100644
> --- a/arch/loongarch/power/suspend_asm.S
> +++ b/arch/loongarch/power/suspend_asm.S
> @@ -78,9 +78,8 @@ SYM_INNER_LABEL(loongarch_wakeup_start, SYM_L_GLOBAL)
>   	li.d		t0, CSR_DMW1_INIT	# CA, PLV0
>   	csrwr		t0, LOONGARCH_CSR_DMWIN1
>   
> -	la.abs		t0, 0f
> -	jr		t0
> -0:
> +	JUMP_LINK_ADDR
> +
>   	la.pcrel	t0, acpi_saved_sp
>   	ld.d		sp, t0, 0
>   	SETUP_WAKEUP