LinuxQuestions.org - ADS7846 linux driver with mediatek devices

Hello!
Trying to add touchscreen ( compatible = "ti,ads7846"; ) to my MT7621 based router through SPI, but it looks like OpenWrt (kernel 5.4.52) doesn't want to route interrupt to ads7846 driver (https://github.com/torvalds/linux/bl...reen/ads7846.c). I've got these lines in device tree:

Code:

....

#include "mt7621.dtsi"

....



    xpt2046reg: xpt2046_reg {

        compatible = "regulator-fixed";

        regulator-name = "xpt2046_vcc";

        regulator-min-microvolt = <3300000>;

        regulator-max-microvolt = <3300000>;

        regulator-always-on;

.....

&spi0 {

    status = "okay";



....



    spidev3@3 {

        #address-cells = <1>;

        #size-cells = <0>;

        compatible = "ralink,mt7621-spi";

        reg = <3>;

        spi-max-frequency = <250000>;

        status = "disabled";

    };

        

    xpt2046@4 {

        compatible = "ti,ads7846";

        reg = <3>;

        vcc-supply = <&xpt2046reg>;

        spi-max-frequency = <250000>;



        interrupt-parent = <&gpio>;

        interrupts = <18 IRQ_TYPE_EDGE_FALLING>;

        pendown-gpio = <&gpio 18 GPIO_ACTIVE_LOW>;

        ti,x-min = /bits/ 16 <0x0>;

        ti,x-max = /bits/ 16 <0x0fff>;

        ti,y-min = /bits/ 16 <0x0>;

        ti,y-max = /bits/ 16 <0x0fff>;

        ti,x-plate-ohms = /bits/ 16 <180>;

        ti,pressure-max = /bits/ 16 <255>;

        ti,debounce-max = /bits/ 16 <10>;

        ti,debounce-tol = /bits/ 16 <5>;

        ti,debounce-rep = /bits/ 16 <1>;

        ti,keep-vref-on = <1>;

        ti,settle-delay-usec = /bits/ 16 <150>;



        wakeup-source;

        status = "okay";

    };

};

Interrupt is successfully registered in the system:

Code:

ads7846 spi0.3: touchscreen, irq 27

Driver is loaded:

Code:

input: ADS7846 Touchscreen as /devices/platform/1e000000.palmbus/1e000b00.spi/spi_master/spi0/spi0.3/input/input0

Event is located in /dev/input/event0. MISO, MOSI, SCK and CS are working on spi0.3 and touchscreen driver is replying something meaningful during driver probe/initialization. There is corresponding line in /proc/interrupts:

Code:

27: 0 0 0 0 1e000600.gpio 18 ads7846

GPIO18 is pulled up externally through 10k resistor. But when touchscreen driver chip pulls down this gpio (pendown) nothing is happening in /proc/interrupts. ads7846_hard_irq() and ads7846_irq() functions from linux driver not even used.

If I remove any reference of GPIO18 in device tree - GPIO18 can be used freely as interrupt source through echo falling > /sys/class/gpio/gpio490/edge, that is clearly seen in /proc/interrupts.

Code:

# cat /proc/bus/input/devices 

I: Bus=0000 Vendor=0000 Product=0000 Version=0000

N: Name="ADS7846 Touchscreen"

P: Phys=spi0.3/input0

S: Sysfs=/devices/platform/1e000000.palmbus/1e000b00.spi/spi_master/spi0/spi0.3/input/input0

U: Uniq=

H: Handlers=event0 

B: PROP=0

B: EV=b

B: KEY=400 0 0 0 0 0 0 0 0 0 0

B: ABS=1000003

How else can I debug this issue?