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

[luojiaxing]

On 2020/12/6 6:15, Serge Semin wrote:
> On Tue, Dec 01, 2020 at 04:59:21PM +0800, luojiaxing wrote:
> > 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.
> Hmm, that sounds like a problem, but the explanation is a bit unclear
> to me. AFAICS you are saying that the only callbacks which are
> called during the IRQ request/release are the irq_enable(), right?


Yes, but one point needs to be clarified, for IRQ requests, it calls 
irq_enable(); for IRQ release, it calls irq_disable().

Actually I am thinking that why only irq_enable()/irq_disable() is 
called since the mask and enable flags of irq_data are both set.

Does IRQ subsystem expect irq_enable to set both mask and enable? If we 
didn't do that, the state machine of the software is different from 
hardware, at least for mask bit.


> If
> so then the only reason why we haven't got a problem reported due to
> that so far is that the IRQs actually unmasked by default.


yes, I think so, Common drivers do not mask the IRQ before releasing it. 
But that's possible.


> In anyway I'd suggest to join someone from the kernel IRQs-related
> subsystem to this discussion to ask their opinion whether the IRQs
> setup procedure is supposed to work like you say and the irq_enable
> shall actually also unmask IRQs.
>
> Thomas, Jason, Mark, could you give us your comment about the issue?
>
> -Sergey
>
> >
> .