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Interrupt Input boots up as Output

Question asked by Steffen Doster on Jun 20, 2020
Latest reply on Jun 23, 2020 by igorpadykov



I have a very strange behavior on an Interrupt Input. The whole story:

I'm running Linux on an i.MX6 Solo Processor on a custom Board. It is connected to a ti-WLAN module WL1837 via SD-Interface.

To operate this module it is necessary to have an interrupt input comming from the module.

I already implemented this on another custom board and it works perfectly. The difference between the two boards are:

- The SD-Interfaces are different (SD2 and SD4)

- The Interrupt Pin is different

- The board I now want to bring up needs a levelshifter because WL1837 Interface is 1.8V and the IOs of the i.MX6 on this board needs to be operated on 3.3V.


I derived the Devicetree-Part for WLAN of the board from the successful implementation of the other board.

But it doesn't work. On bootup there are plenty error messages that the Kernel can't get the module to work.

(on Monday I will provide detailed Error-Messages and Devicetree codes)

After long research I found the failure:
The Interrupt pin on i.MX6 seems to be configured as Output Pin with '0' assigned.

When I switch it to Input (by the old fashioned way: echo gpio-number to export and setting direction in this gpio) I can bring up the WLAN-module perfectly. Then everything works like it has to.


The problematic Pin is NANDF_CS3 configured as GPIO6_IO16 thus it is linux gpio 176.


Why does Linux configure this Interrupt-Input as Output? How can this be possible? I checked and checked again my IO-Muxing and the other configurations in Devicetree but didn't find an error yet. Can you give me any hint or help?


On Monday I will provide more information like devicetree and error messages. Just say what you need to help me.




I have now attached parts of my devicetree. My DT is seperated in several files sorted by bus/interfaces or functions.

The base.dtsi represents my base system with thins that nearly never change and where everything else is attached to.

I think iomux.dtsi and usdhc.dtsi is self explaining.


I also forgot to mention:

I'm using Linux-Kernel 4.19.127 and Debian 9 on this device.


The relevant code-snippet (as I think):


pinctrl_hog: hoggrp {
fsl,pins = <
MX6QDL_PAD_NANDF_D0__GPIO2_IO00 0x1b0b0     /* LED CAN Run */
MX6QDL_PAD_NANDF_D1__GPIO2_IO01 0x1b0b0     /* LED CAN Error */
MX6QDL_PAD_NANDF_D3__GPIO2_IO03 0x1b0b0     /* 5V 12V Poweroff */
MX6QDL_PAD_NANDF_D4__GPIO2_IO04 0x1b0b0     /* Dig Out 0 */
MX6QDL_PAD_NANDF_D5__GPIO2_IO05 0x1b0b0     /* Dig Out 1 */
MX6QDL_PAD_NANDF_D6__GPIO2_IO06 0x1b0b0     /* Dig Out 2 */
MX6QDL_PAD_NANDF_CS0__GPIO6_IO11 0x1b0b0   /* Dig In 0 */
MX6QDL_PAD_NANDF_CS1__GPIO6_IO14 0x1b0b0   /* Dig In 1 */
MX6QDL_PAD_NANDF_CS2__GPIO6_IO15 0x1b0b0   /* Dig In 2 */
MX6QDL_PAD_NANDF_CS3__GPIO6_IO16 0x1b0b0   /* WLAN Interrupt */
MX6QDL_PAD_GPIO_3__GPIO1_IO03 0x1b0b0            /* USB H1 PWR En */
MX6QDL_PAD_EIM_D29__GPIO3_IO29 0x1b0b0          /* USB OTG PWR En */


pinctrl_wlan_vmmc: wlan_vmmcgrp {
fsl,pins = <
MX6QDL_PAD_NANDF_D7__GPIO2_IO07 0x13059 /* WLAN Enable */


pinctrl_usdhc4: usdhc4grp {
fsl,pins = <
MX6QDL_PAD_SD4_DAT0__SD4_DATA0 0x17059
MX6QDL_PAD_SD4_DAT1__SD4_DATA1 0x17059
MX6QDL_PAD_SD4_DAT2__SD4_DATA2 0x17059
MX6QDL_PAD_SD4_DAT3__SD4_DATA3 0x17059


WLAN Enable Regulator:

reg_wlan_vmmc: regulator@5 {
compatible = "regulator-fixed";
reg = <5>;
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_wlan_vmmc>;
regulator-name = "reg_wlan_vmmc";
regulator-min-microvolt = <3300000>;
regulator-max-microvolt = <3300000>;
gpio = <&gpio2 7 GPIO_ACTIVE_HIGH>;
startup-delay-us = <70000>;


The USDHC-Interface the WLAN-Module is attached to:

usdhc4: usdhc@0219c000 {
compatible = "fsl,imx6q-usdhc";
reg = <0x0219c000 0x4000>;
interrupts = <0 25 IRQ_TYPE_LEVEL_HIGH>;
clocks = <&clks IMX6QDL_CLK_USDHC4>,
clock-names = "ipg", "ahb", "per";
bus-width = <4>;
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_usdhc4>;
vmmc-supply = <&reg_wlan_vmmc>;
status = "okay";


#address-cells = <1>;
#size-cells = <0>;
wlcore: wlcore@0 {
compatible = "ti,wl1837";
reg = <0>;
interrupt-parent = <&gpio6>;
interrupts = <16 IRQ_TYPE_LEVEL_HIGH>;



Do you need more informations?