Re: [PATCH] pinctrl-baytrail: fix for irq descriptor conflict on ASUS T100TA

["Jin, Yao" <yao.jin@linux.intel.com>]

On 2014/4/19 4:44, Benjamin Tissoires wrote:
> On Wed, Apr 16, 2014 at 8:05 AM, Jin Yao <yao.jin@linux.intel.com> wrote:
>> A crash is triggered on the ASUS T100TA Baytrail-T because of a irq
>> descriptor conflict. There are two gpio triggered acpi events in this
>> device, GPIO 6 and 18. These gpios are translated to irqs by calling
>> gpio_to_irq which in turn will call irq_create_mapping(vg->domain, offset).
>> irq_create_mapping will take care of allocating the irq descriptor, taking
>> the first available number starting from the given value (6 in our case).
>> The 0-15 are already reserved by legacy ISA code, so it gets the first
>> free irq descriptor which is number 16. The i915 driver also uses irq 16,
>> it loads later than gpio and crashes in probe.
>>
>> The bug is reported here:
>> https://bugzilla.kernel.org/show_bug.cgi?id=68291
> 
> Adam, the reporter of this bug told me that his touchscreen was broken
> in its tablet.
This bug is triggered when system boots, or rather, it's triggered in
i915 probe, because i915 still uses irq 16 but it's allocated for gpio
yet. It's not a touchscreen case.

> I strongly suspect this patch to be the root cause of this, because
> the touchscreen uses i2c_hid. i2c_hid relies on an IRQ declared in the
> DSDT when it is acpi enumerated, and since the inclusion of this
> patch, no irq are triggered from a driver point of view.
> 
> Adam should still confirm that the revert of the patch makes the
> touchscreen back alive, but if I understood correctly the bug report,
> without the patch, his tablet oopses at boot.
Do you mean this patch cause the touchscreen doesn't work? I suspect
that because the touch screen works on my T100 with this patch.

> 
> Still, it would be good if you could check that shifting the irqs in
> the pinctrl is or is not a problem with the irqs used for i2c devices
> (and others) declared in the dsdt.
I checked DSDT of ASUS T100, looks no irq conflict after irq shifting.

> 
> Cheers,
> Benjamin
> 
>>
>> The rootcause we know now is a low level irq issue. It needs a long term
>> solution to fix the issue in irq system.
>>
>> This patch changes the Baytrail GPIO driver to avoid the irq descriptor
>> conflict. It still uses the irq domain to allocate irq descriptor but start
>> from a predefined irq base number (256) to avoid the conflict.
>>
>> Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
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