linux-kernel - Re: [PATCH v4 07/10] drivers: pinctrl: msm: setup GPIO irqchip hierarchy

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Date:   Thu, 21 Mar 2019 14:54:35 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Marc Zyngier <marc.zyngier@....com>
Cc:     Lina Iyer <ilina@...eaurora.org>, evgreen@...omium.org,
        linux-kernel@...r.kernel.org, rplsssn@...eaurora.org,
        linux-arm-msm@...r.kernel.org, thierry.reding@...il.com,
        bjorn.andersson@...aro.org, dianders@...omium.org,
        linus.walleij@...aro.org
Subject: Re: [PATCH v4 07/10] drivers: pinctrl: msm: setup GPIO irqchip hierarchy

Quoting Marc Zyngier (2019-03-16 04:39:48)
> On Fri, 15 Mar 2019 09:28:31 -0700
> Stephen Boyd <swboyd@...omium.org> wrote:
> 
> > Quoting Lina Iyer (2019-03-13 14:18:41)
> > > @@ -994,6 +1092,22 @@ static int msm_gpio_init(struct msm_pinctrl *pctrl)
> > >         pctrl->irq_chip.irq_request_resources = msm_gpio_irq_reqres;
> > >         pctrl->irq_chip.irq_release_resources = msm_gpio_irq_relres;
> > >  
> > > +       chip->irq.chip = &pctrl->irq_chip;
> > > +       chip->irq.domain_ops = &msm_gpio_domain_ops;
> > > +       chip->irq.handler = handle_edge_irq;
> > > +       chip->irq.default_type = IRQ_TYPE_EDGE_RISING;  
> > 
> > This also changed from v3. It used to be IRQ_TYPE_NONE. Specifying this
> > here seems to cause gpiolib to print a WARN.
> > 
> > 
> >         /*
> >          * Specifying a default trigger is a terrible idea if DT or ACPI is
> >          * used to configure the interrupts, as you may end up with
> >          * conflicting triggers. Tell the user, and reset to NONE.
> >          */
> >         if (WARN(np && type != IRQ_TYPE_NONE,
> >                  "%s: Ignoring %u default trigger\n", np->full_name, type))
> >                 type = IRQ_TYPE_NONE;
> > 
> > 
> > So I guess this change should be dropped. Or at the least, it should be
> > split out to it's own patch and the motivations can be discussed in the
> > commit text.
> 
> It is something I requested (although I expected this to be a
> different patch, and even a clarification would have been OK).
> 
> One way or another, the default trigger must match the flow handler. If
> we set it up with IRQ_TYPE_NONE, what does it mean? The fact that
> IRQ_TYPE_NONE acts as a wildcard doesn't mean the handle_edge_irq flow
> handler is a good match for all interrupt types (it is rarely OK for
> level interrupts).

I think this is a question for Thierry or Linus. I'm not sure why this
check was put in place in the code. I tried to dig into it really quick
but I didn't find anything obvious and then I gave up.

Maybe with hierarchical irqdomains we can drop this check? I don't think
the gpiolib core ever uses this 'default_type' or 'handler' for anything
once we replace the irqdomain that's used for a particular gpiochip with
a custom irqdomain. The only user I see, gpiochip_irq_map(), won't ever
be called so it really ends up being a thing that the driver specific
irqdomains should check for and reject when parsing the DT and it sees
IRQ_TYPE_NONE come out.

------8<-------
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 144af0733581..fe2f7888c473 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1922,7 +1922,7 @@ static int gpiochip_add_irqchip(struct gpio_chip *gpiochip,
 	 * used to configure the interrupts, as you may end up with
 	 * conflicting triggers. Tell the user, and reset to NONE.
 	 */
-	if (WARN(np && type != IRQ_TYPE_NONE,
+	if (WARN(!gpiochip->irq.domain_ops && np && type != IRQ_TYPE_NONE,
 		 "%s: Ignoring %u default trigger\n", np->full_name, type))
 		type = IRQ_TYPE_NONE;