Re: [PATCH RESEND] pinctrl: mediatek: Fix trigger type setting follow for unexpected interrupt

[mtk15103 <hailong.fan@mediatek.com>]

On Thu, 2021-01-21 at 20:13 +0800, Nicolas Boichat wrote:
> On Thu, Jan 21, 2021 at 8:09 PM mtk15103 <hailong.fan@mediatek.com> wrote:
> >
> > On Thu, 2021-01-21 at 16:55 +0800, Nicolas Boichat wrote:
> > > On Thu, Jan 21, 2021 at 3:52 PM Hailong Fan <hailong.fan@mediatek.com> wrote:
> > > >
> > > > When flipping the polarity will be generated interrupt under certain
> > > > circumstances, but GPIO external signal has not changed.
> > > > Then, mask the interrupt before polarity setting, and clear the
> > > > unexpected interrupt after trigger type setting completed.
> > > >
> > > > Signed-off-by: Hailong Fan <hailong.fan@mediatek.com>
> > > > ---
> > > > Resend since some server reject.
> > > > ---
> > > >  drivers/pinctrl/mediatek/mtk-eint.c | 13 +++++++++++--
> > > >  1 file changed, 11 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/pinctrl/mediatek/mtk-eint.c b/drivers/pinctrl/mediatek/mtk-eint.c
> > > > index 22736f60c16c..3acda6bb401e 100644
> > > > --- a/drivers/pinctrl/mediatek/mtk-eint.c
> > > > +++ b/drivers/pinctrl/mediatek/mtk-eint.c
> > > > @@ -157,6 +157,7 @@ static void mtk_eint_ack(struct irq_data *d)
> > > >  static int mtk_eint_set_type(struct irq_data *d, unsigned int type)
> > > >  {
> > > >         struct mtk_eint *eint = irq_data_get_irq_chip_data(d);
> > > > +       unsigned int unmask;
> > >
> > > bool?
> > Yes,thanks.
> > >
> > > >         u32 mask = BIT(d->hwirq & 0x1f);
> > > >         void __iomem *reg;
> > > >
> > > > @@ -173,6 +174,13 @@ static int mtk_eint_set_type(struct irq_data *d, unsigned int type)
> > > >         else
> > > >                 eint->dual_edge[d->hwirq] = 0;
> > > >
> > > > +       if (!mtk_eint_get_mask(eint, d->hwirq)) {
> > > > +               mtk_eint_mask(d);
> > > > +               unmask = 1;
> > > > +       } else {
> > > > +               unmask = 0;
> > > > +       }
> > > > +
> > > >         if (type & (IRQ_TYPE_LEVEL_LOW | IRQ_TYPE_EDGE_FALLING)) {
> > > >                 reg = mtk_eint_get_offset(eint, d->hwirq, eint->regs->pol_clr);
> > > >                 writel(mask, reg);
> > > > @@ -189,8 +197,9 @@ static int mtk_eint_set_type(struct irq_data *d, unsigned int type)
> > > >                 writel(mask, reg);
> > > >         }
> > > >
> > > > -       if (eint->dual_edge[d->hwirq])
> > > > -               mtk_eint_flip_edge(eint, d->hwirq);
> > >
> > > Why are you dropping this? Aren't we at risk to miss the first edge
> > > after mtk_eint_set_type is called?
> > mtk_eint_unmask() will do it.
> > If unmask != 1, user need to call mtk_eint_unmask() to enable the
> > interrupt before use it, thanks.
> 
> Makes sense, I just have one more worry:
> https://elixir.bootlin.com/linux/latest/source/drivers/pinctrl/mediatek/mtk-eint.c#L122
> 
> mtk_eint_unmask unmasks the interrupt _before_ the edge is flipped,
> could this cause a spurious interrupt? On any unmask operation -- not
> just on mtk_eint_set_type (so this is technically another problem,
> that should be fixed as a separate patch)

This situation will not happen.

Spurious interrupt occur condition: edge irq polarity value is same with
input signal. 
e.g.
Default value: GPIO input is high, trigger type is falling_edge.
User want modify trigger type is rising_edge under some certain
circumstances, it will generate spurious interrupt but external signal
maintain high.
So we need ack interrupt after trigger_type setting is completed.

mtk_eint_flip_edge is for dual_edge, the polarity setting based on
current gpio input signal:
if (input == high)
	polarity = low; /* falling_edge */
else
	polarity = high; /* rising_edge */
Then it's not cause a spurious interrupt.
> > > > +       mtk_eint_ack(d);
> > > > +       if (unmask == 1)
> > >
> > > Just `if (unmask)`
> > Yes,thanks.
> > > > +               mtk_eint_unmask(d);
> > > >
> > > >         return 0;
> > > >  }
> > > > --
> > > > 2.18.0
> >