linux-kernel - Re: Loongson (and other $ARCHs?) idle VS timer enqueue

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Date:   Wed, 26 Apr 2023 08:46:54 +0800
From:   maobibo <maobibo@...ngson.cn>
To:     WANG Xuerui <kernel@...0n.name>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Frederic Weisbecker <frederic@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Huacai Chen <chenhuacai@...nel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Anna-Maria Behnsen <anna-maria@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: Loongson (and other $ARCHs?) idle VS timer enqueue



在 2023/4/25 21:28, WANG Xuerui 写道:
> On 2023/4/25 21:25, maobibo wrote:
>>
>>
>> 在 2023/4/25 19:49, Peter Zijlstra 写道:
> 
> <snip>
> 
>>>
>>> diff --git a/arch/loongarch/kernel/genex.S b/arch/loongarch/kernel/genex.S
>>> index 44ff1ff64260..3c8a6bab98fe 100644
>>> --- a/arch/loongarch/kernel/genex.S
>>> +++ b/arch/loongarch/kernel/genex.S
>>> @@ -18,27 +18,31 @@
>>>         .align    5
>>>   SYM_FUNC_START(__arch_cpu_idle)
>>> -    /* start of rollback region */
>>> -    LONG_L    t0, tp, TI_FLAGS
>>> -    nop
>>> -    andi    t0, t0, _TIF_NEED_RESCHED
>>> -    bnez    t0, 1f
>>> -    nop
>>> -    nop
>>> -    nop
>>> +    /* start of idle interrupt region */
>>> +    move    t0, CSR_CRMD_IE
>> addi.d  t0, zero, CSR_CRMD_IE can be used here, move is used for reg to reg
> 
> Or better: li.d t0, CSR_CRMD_IE (prefer pseudo-instruction over concrete ones whenever it helps readability). We don't need to support ancient in-house toolchains without support for even li. ;-)
  
I am not familiar with compiler:(, how many actual instructions does
pseudo-instr li.d takes? It will be ok if it uses only one intr, else
there will be problem.

Regards
Bibo, Mao

>