i.MX ProcessorsのトピックCannot export specific gpio pins. How to check what uses GPIO pins?

Cannot export specific gpio pins. How to check what uses GPIO pins?

Hirotoshi_Sato — Thu, 07 Sep 2017 08:49:49 GMT

Hi,

I use an i.mx6 board and am configuring a device tree.

I changed a dts file and put the dtb file in a boot partition.

I set GPIO4_IO19 in dts file as follows.

&iomuxc {
pinctrl-names = "default";
pinctrl-0 = <&pinctrl_hog_1>;
imx6ul-evk {
pinctrl_hog_1: hoggrp-1 {
fsl,pins = <
...
MX6UL_PAD_CSI_VSYNC__GPIO4_IO19 0x0000B0B0
...
>;
};
...

At first MX6UL_PAD_CSI_VSYNC__GPIO4_IO19 was defined in other group (usdhcgrp) but I commented out them.

After booting, I checked if gpio is successfully determined as I set.

The result is

echo 115 > /sys/class/gpio/export
-sh: echo: write error: Device or resource busy

So I checked this.

cat /sys/kernel/debug/gpio

GPIOs 0-31, platform/209c000.gpio, 209c000.gpio:
gpio-10 (phy-reset ) out lo
GPIOs 32-63, platform/20a0000.gpio, 20a0000.gpio:
GPIOs 64-95, platform/20a4000.gpio, 20a4000.gpio:
gpio-68 (ft5x06_irq_gpio ) in hi
GPIOs 96-127, platform/20a8000.gpio, 20a8000.gpio:
gpio-109 (? ) out lo
gpio-115 (cd ) in lo
gpio-116 (? ) out lo
gpio-117 (? ) out lo
gpio-118 (sysfs ) in hi
GPIOs 128-159, platform/20ac000.gpio, 20ac000.gpio:
gpio-128 (phy-reset ) out lo

gpio-115 is used by cd. What is cd ?

I want to use it as sysfs to read the state. Any other way to read it ?

Furthermore, gpio-10, 68, 109, 116, 117 is used by other device.

How can I use them by sysfs?

Thank you for your cooperation.

Re: Cannot export specific gpio pins. How to check what uses GPIO pins?

igorpadykov — Thu, 07 Sep 2017 10:20:30 GMT

Hi Hirotoshi

please look at

How do can I find out which Linux driver is hogging my GPIO? - Stack Overflow

Best regards
igor

Re: Cannot export specific gpio pins. How to check what uses GPIO pins?

Hirotoshi_Sato — Thu, 07 Sep 2017 11:07:02 GMT

Hi igor,

Thank you for your answer.

I am afraid that I have read the link and it would not help me.

(This time the using device is ?, so I cannot find.)

I think dts file is related to this issue 'cause I think only dts file includes pin control, but I couldn't find out.

Would you give me any other adivice?

Best regards,

Hiro

Re: Cannot export specific gpio pins. How to check what uses GPIO pins?

igorpadykov — Thu, 07 Sep 2017 23:53:51 GMT

Hi Hiro

as these are general linux questions, it may be posted

on kernel mail lists.

Majordomo Lists at VGER.KERNEL.ORG

Best regards
igor

Re: Cannot export specific gpio pins. How to check what uses GPIO pins?

Hirotoshi_Sato — Thu, 21 Sep 2017 07:20:21 GMT

Hi igor,

Thank you for your replying.

I found my dts file has woding about the gpio.

At first I think gpio is only defined in &iomuxc {...} in dts, but there are other definition in the dts file.

Best regards

Re: Cannot export specific gpio pins. How to check what uses GPIO pins?

BiyongSUN — Thu, 21 Sep 2017 08:44:30 GMT

i.MX Development Miscellanea(i.MX 开发杂记)
https://community.nxp.com/docs/DOC-335198

Accessing GPIO From UserSpace