linux-kernel - Re: [RFC PATCH] genirq: Avoid unnecessary low level irq function calls

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Date:   Mon, 26 Jun 2017 17:57:38 +0800
From:   jeffy <jeffy.chen@...k-chips.com>
To:     Thomas Gleixner <tglx@...utronix.de>
CC:     linux-kernel@...r.kernel.org, briannorris@...omium.org,
        dianders@...omium.org, tfiga@...omium.org
Subject: Re: [RFC PATCH] genirq: Avoid unnecessary low level irq function
 calls

Hi Thomas,

thanx for your comments.

On 06/26/2017 04:20 PM, Thomas Gleixner wrote:
> Jeffy,
>
> On Mon, 26 Jun 2017, Jeffy Chen wrote:
>>   void irq_enable(struct irq_desc *desc)
>>   {
>> -	irq_state_clr_disabled(desc);
>> -	if (desc->irq_data.chip->irq_enable)
>> -		desc->irq_data.chip->irq_enable(&desc->irq_data);
>> -	else
>> -		desc->irq_data.chip->irq_unmask(&desc->irq_data);
>> -	irq_state_clr_masked(desc);
>> +	if (irqd_is_started(&desc->irq_data) &&
>> +	    !irqd_irq_disabled(&desc->irq_data)) {
>> +		unmask_irq(desc);
>
> I'm having a hard time to understand the logic here.
>
>      if (started && !disabled)
>      	unmask()
>
> That does not make any sense. If you need that to work around a state
> inconsistency then it needs to be addressed there and not worked around
> here.
right, we already set disabled state in desc_set_defaults, so the 
disabled state should be consistency here. so just
if(!disabled)
   unmask()
else
   enable()
?

and i saw we didn't set masked state in desc_set_defaults, i'll send a 
patch for that, and remove unmask_irq's started check too.
>
>> +	} else {
>> +		irq_state_clr_disabled(desc);
>> +		if (desc->irq_data.chip->irq_enable) {
>> +			desc->irq_data.chip->irq_enable(&desc->irq_data);
>> +			irq_state_clr_masked(desc);
>> +		} else {
>> +			unmask_irq(desc);
>> +		}
>> +	}
>>   }
>>
>>   static void __irq_disable(struct irq_desc *desc, bool mask)
>>   {
>> -	irq_state_set_disabled(desc);
>> -	if (desc->irq_data.chip->irq_disable) {
>> -		desc->irq_data.chip->irq_disable(&desc->irq_data);
>> -		irq_state_set_masked(desc);
>> -	} else if (mask) {
>> -		mask_irq(desc);
>> +	if (irqd_irq_disabled(&desc->irq_data)) {
>> +		if (mask)
>> +			mask_irq(desc);
>> +	} else {
>> +		irq_state_set_disabled(desc);
>> +		if (desc->irq_data.chip->irq_disable) {
>> +			desc->irq_data.chip->irq_disable(&desc->irq_data);
>> +			irq_state_set_masked(desc);
>> +		} else if (mask) {
>> +			mask_irq(desc);
>> +		}
>>   	}
>>   }
>>
>> @@ -311,18 +322,21 @@ void irq_percpu_disable(struct irq_desc *desc, unsigned int cpu)
>>
>>   static inline void mask_ack_irq(struct irq_desc *desc)
>>   {
>> -	if (desc->irq_data.chip->irq_mask_ack)
>> +	if (desc->irq_data.chip->irq_mask_ack) {
>>   		desc->irq_data.chip->irq_mask_ack(&desc->irq_data);
>> -	else {
>> -		desc->irq_data.chip->irq_mask(&desc->irq_data);
>> +		irq_state_set_masked(desc);
>> +	} else {
>> +		mask_irq(desc);
>>   		if (desc->irq_data.chip->irq_ack)
>>   			desc->irq_data.chip->irq_ack(&desc->irq_data);
>>   	}
>> -	irq_state_set_masked(desc);
>>   }
>>
>>   void mask_irq(struct irq_desc *desc)
>>   {
>> +	if (irqd_irq_masked(&desc->irq_data))
>> +		return;
>> +
>>   	if (desc->irq_data.chip->irq_mask) {
>>   		desc->irq_data.chip->irq_mask(&desc->irq_data);
>>   		irq_state_set_masked(desc);
>> @@ -331,6 +345,10 @@ void mask_irq(struct irq_desc *desc)
>>
>>   void unmask_irq(struct irq_desc *desc)
>>   {
>> +	if (irqd_is_started(&desc->irq_data) &&
>> +	    !irqd_irq_masked(&desc->irq_data))
>> +		return;
>
> Ditto.
>
> Thanks,
>
> 	tglx
>
>
>