linux-kernel - Re: [PATCH v1] gpio: dwapb: mask/unmask IRQ when disable/enable it

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Date:   Tue, 1 Dec 2020 16:59:21 +0800
From:   luojiaxing <luojiaxing@...wei.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
CC:     <bgolaszewski@...libre.com>, <linus.walleij@...aro.org>,
        <Sergey.Semin@...kalelectronics.ru>, <linux-gpio@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linuxarm@...wei.com>
Subject: Re: [PATCH v1] gpio: dwapb: mask/unmask IRQ when disable/enable it


On 2020/11/30 19:22, Andy Shevchenko wrote:
> On Mon, Nov 30, 2020 at 05:36:19PM +0800, Luo Jiaxing wrote:
>> The mask and unmask registers are not configured in dwapb_irq_enable() and
>> dwapb_irq_disable(). In the following situations, the IRQ will be masked by
>> default after the IRQ is enabled:
>>
>> mask IRQ -> disable IRQ -> enable IRQ
>>
>> In this case, the IRQ status of GPIO controller is inconsistent with it's
>> irq_data too. For example, in __irq_enable(), IRQD_IRQ_DISABLED and
>> IRQD_IRQ_MASKED are both clear, but GPIO controller do not perform unmask.
> Sounds a bit like a papering over the issue which is slightly different.
> Can you elaborate more, why ->irq_mask() / ->irq_unmask() are not being called?


Sure, The basic software invoking process is as follows:

Release IRQ:
free_irq() -> __free_irq() -> irq_shutdown() ->__irq_disable()

Disable IRQ:
disable_irq() -> __disable_irq_nosync() -> __disable_irq -> irq_disable 
-> __irq_disable()

As shown before, both will call __irq_disable(). The code of it is as 
follows:

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);
     }
}

Because gpio-dwapb.c provides the hook function of irq_disable, 
__irq_disable() will directly calls chip->irq_disable() instead of 
mask_irq().

For irq_enable(), it's similar and the code is as follows:

if (!irqd_irq_disabled(&desc->irq_data)) {
     unmask_irq(desc);
} 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);
     }
}

Similarly, because gpio-dwapb.c provides the hook function of 
irq_enable, irq_enable() will directly calls chip->irq_enable() but does 
not call unmask_irq().


Therefore, the current handle is as follows:

API of IRQ:        |   mask_irq()             | disable_irq()            
|    enable_irq()

gpio-dwapb.c:  |   chip->irq_mask()   | chip->irq_diable()   |    
chip->irq_enable()

I do not know why irq_enable() only calls chip->irq_enable(). However, 
the code shows that irq_enable() clears the disable and masked flags in 
the irq_data state.

Therefore, for gpio-dwapb.c, I thinks ->irq_enable also needs to clear 
the disable and masked flags in the hardware register.