linux-kernel - Re: [PATCH v4 2/3] irqchip/loongson-eiointc: Skip handling if there is no pending irq

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Message-ID: <3d8cdc3a-415c-0f5a-d8d5-3fd2084926fc@loongson.cn>
Date: Tue, 30 Jan 2024 11:23:29 +0800
From: maobibo <maobibo@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>
Cc: Jiaxun Yang <jiaxun.yang@...goat.com>,
 Thomas Gleixner <tglx@...utronix.de>, linux-mips@...r.kernel.org,
 linux-kernel@...r.kernel.org, Sergey Shtylyov <s.shtylyov@....ru>,
 lvjianmin@...ngson.cn
Subject: Re: [PATCH v4 2/3] irqchip/loongson-eiointc: Skip handling if there
 is no pending irq



On 2024/1/29 下午8:27, Huacai Chen wrote:
> Hi, Bibo,
> 
> As commented in another patch, you can use eiointc_irq_dispatch(),
> iocsr_read64() to describe functions, and it is better to use
> Loongson-3A5000, Loongson-2K2000, Loongson-2K0500 rather than 3A5000,
> 2K2000, 2K0500. Besides, please always use IRQs rather than IRQS.
Huacai,

Thanks for reviewing.

Will do in next patch.

Regards
Bibo Mao
> 
> With these modifications,
> 
> Acked-by: Huacai Chen <chenhuacai@...ngson.cn>
> 
> On Thu, Jan 25, 2024 at 7:36 PM Bibo Mao <maobibo@...ngson.cn> wrote:
>>
>> It is one simple optimization in the interrupt dispatch function
>> eiointc_irq_dispatch. There are 256 IRQs supported for eiointc on
>> 3A5000 and 2K2000 platform, 128 IRQS on 2K0500 platform, eiointc irq
>> handler reads the bitmap and find pending irqs when irq happens. So
>> there are several consecutive iocsr_read64 operations for the all
>> bits to find all pending irqs. If the pending bitmap is zero, it
>> means that there is no pending irq for the this irq bitmap range,
>> we can skip handling to avoid some useless operations such as
>> clearing hw ISR.
>>
>> Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
>> ---
>>   drivers/irqchip/irq-loongson-eiointc.c | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> diff --git a/drivers/irqchip/irq-loongson-eiointc.c b/drivers/irqchip/irq-loongson-eiointc.c
>> index b3736bdd4b9f..6a71a8c29ac7 100644
>> --- a/drivers/irqchip/irq-loongson-eiointc.c
>> +++ b/drivers/irqchip/irq-loongson-eiointc.c
>> @@ -198,6 +198,12 @@ static void eiointc_irq_dispatch(struct irq_desc *desc)
>>
>>          for (i = 0; i < eiointc_priv[0]->vec_count / VEC_COUNT_PER_REG; i++) {
>>                  pending = iocsr_read64(EIOINTC_REG_ISR + (i << 3));
>> +
>> +               /* Skip handling if pending bitmap is zero */
>> +               if (!pending)
>> +                       continue;
>> +
>> +               /* Clear the IRQs */
>>                  iocsr_write64(pending, EIOINTC_REG_ISR + (i << 3));
>>                  while (pending) {
>>                          int bit = __ffs(pending);
>> --
>> 2.39.3
>>