Configuring bias on an APCI GpioInt

["Jamie McClymont" <jamie@xxxxxxxxxx>]

Hi again,

I have run into a second GPIO issue while writing a driver for the fingerprint sensor in my laptop*, configured in the ACPI table like so:

   Method (_CRS, 0, Serialized)  // _CRS: Current Resource Settings
   {
       Name (RBUF, ResourceTemplate ()
       {
           // SPI
           SpiSerialBusV2 (0x0000, PolarityLow, FourWireMode, 0x08,
               ControllerInitiated, 0x00989680, ClockPolarityLow,
               ClockPhaseFirst, "\\_SB.PCI0.SPI1",
               0x00, ResourceConsumer, , Exclusive,
               )

           // Interrupt
           GpioInt (Level, ActiveLow, ExclusiveAndWake, PullUp, 0x0000,
               "\\_SB.PCI0.GPI0", 0x00, ResourceConsumer, ,
               )
               {   // Pin list
                   0x0000
               }

           // Reset
           GpioIo (Exclusive, PullUp, 0x0000, 0x0000, IoRestrictionOutputOnly,
               "\\_SB.PCI0.GPI0", 0x00, ResourceConsumer, ,
               )
               {   // Pin list
                   0x0008
               }
       })
       CreateWordField (RBUF, 0x3B, GPIN)
       CreateWordField (RBUF, 0x63, SPIN)
       GPIN = GNUM (0x02000017)
       SPIN = GNUM (0x0202000A)
       Return (RBUF) /* \_SB_.SPBA._CRS.RBUF */
   }

I call devm_request_threaded_irq with the number provided in the irq field of the `struct spi_device` during the spi_probe.

This configures the right IRQ number, and it triggers when it should, but it stays asserted for 140ms-600ms after it should have been cleared.

Given it's an active-low level-triggered interrupt with a pull-up requested by the acpi table, my theory is:

* The interrupt line is driven open-drain by the peripheral
* The pullup is not being correctly configured
* It is slooooowly pulled up by leakage current of the GPIO input, hence the interrupt being cleared after 140-600ms

Looking at traces and confirming by source code**, it seems that no code ever attempts to configure the pin's bias during the irq setup.

Is this a bug, or should I be manually setting up the GPIO some other way before requesting the IRQ?

Thanks
- Jamie McClymont


*Hardware details
==============

Laptop is a Huawei Matebook X Pro
CPU is an Intel i5-8250U (the specific pinctrl is pinctrl_sunrisepoint)
Fingerprint Sensor is a Goodix GXFP5187 (not well-documented anywhere, I'm working through reverse-engineering)

** Tested on 5.9-rc8, but I've been reading the source of linux-next and haven't picked up on any relevant differences