linux-kernel - Re: [Regression] "irqdomain: Don't set type when mapping an IRQ" breaks nexus7 gpio buttons

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Date:	Fri, 5 Aug 2016 16:45:26 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	Jon Hunter <jonathanh@...dia.com>
Cc:	Marc Zyngier <marc.zyngier@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	lkml <linux-kernel@...r.kernel.org>,
	Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [Regression] "irqdomain: Don't set type when mapping an IRQ"
 breaks nexus7 gpio buttons

On Mon, Aug 1, 2016 at 3:26 AM, Jon Hunter <jonathanh@...dia.com> wrote:
> Hi John,
>
> On 30/07/16 05:39, John Stultz wrote:
>> Hey Jon,
>>   So after rebasing my nexus7 patch stack onto pre-4.8-rc1 tree, I
>> noticed the power/volume buttons stopped working.
>>
>> I did a manual rebased bisection and chased it down to your commit
>> 1e2a7d78499e ("irqdomain: Don't set type when mapping an IRQ").
>>
>> Reverting that patch makes things work again, so I wanted to see if
>> there was any debugging info I could provide to try to help narrow
>> down the problem here. (Sorry, I'd tinker myself with it some and try
>> to debug the issue, but after burning my friday night on this, I'm
>> eager to get away from the keyboard for the weekend).
>
> Before this commit bad IRQ type settings in device-tree were not getting
> reported and so failures to set the IRQ type were going unnoticed. It's
> most likely a bad IRQ type settings somewhere.
>
> As Thomas mentioned hopefully dmesg will shed a bit more light.
>
> Otherwise it can be worth looking at the ->irq_set_type() function for
> the irqchips in the path of the interrupt requested to see if any are
> failing. Looking at the nexus7 (assuming qcom variant), it looks like
> there are 3 irqchips in the path (pm8921 --> apq8064-pinctrl --> gic).
> The pm8xxx_irq_set_type() could return a failure when setting up the IRQ
> type and could be worth checking. It does not look like the set_type for
> the apq8064-pinctrl should ever fail (apart from calling BUG() which
> would be obvious). The gic can also return a failure for setting the
> type, but I did not see anything at first glance that looks incorrect in
> the dts.
>
> If we can narrow down irqchip, then hopefully it will be clearer.

The pm_8xxx_irq_set_type doesn't seem to be failing as far as I can see..

Looking at the patch that seems to cause the trouble, I narrowed it
down to just the following chunk:

@@ -614,7 +615,11 @@ unsigned int irq_create_fwspec_mapping(struct
irq_fwspec *fwspec)
                 * it now and return the interrupt number.
                 */
                if (irq_get_trigger_type(virq) == IRQ_TYPE_NONE) {
-                       irq_set_irq_type(virq, type);
+                       irq_data = irq_get_irq_data(virq);
+                       if (!irq_data)
+                               return 0;
+
+                       irqd_set_trigger_type(irq_data, type);
                        return virq;
                }

If I revert just that, it works again.

I was worried we were hitting an early failure from !irq_data, but it
seems there's some subtle difference between irqd_set_trigger_type and
irq_set_type that makes the former break for me.

Still digging though.

thanks
-john