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

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Message-ID: <effce90b-f035-5502-4aa6-0f222406cd17@loongson.cn>
Date:   Sat, 14 Jan 2023 15:25:42 +0800
From:   Youling Tang <tangyouling@...ngson.cn>
To:     Jinyang He <hejinyang@...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

Hi, Jinyang

On 01/14/2023 02:40 PM, Jinyang He wrote:
>
> 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.

Ok, I will modify it as follows：

         .macro JUMP_CACHE_ADDR temp1 temp2
         li.d    \temp1, CACHE_BASE
         pcaddi  \temp2, 0
         or      \temp1, \temp1, \temp2
         jirl    zero, \temp1, 0xc
         .endm

There is also an alternative name "JUMP_DMW1_ADDR" for discussion.

Thanks,
Youling

>
>
> 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
>