topic Does imx.6 device tree gpio config just need to set bit 31 as high? in i.MX Processors

Does imx.6 device tree gpio config just need to set bit 31 as high?

wallyyeh — Mon, 17 Oct 2016 08:10:32 GMT

Hi, guys:

Recently I'm trying kernel 4.1(I was working in kernel 3.0.35 for a long time), now one question is made me crazy:

Does gpio's config in device tree always just set bit 31 as high(and leave all ohter bits 0)?

In arch/arm/boot/dts/imx6qdl-sabresd.dtsi:

pinctrl_hog: hoggrp {
fsl,pins = <
MX6QDL_PAD_NANDF_D0__GPIO2_IO00 0x80000000
MX6QDL_PAD_NANDF_D1__GPIO2_IO01 0x80000000
MX6QDL_PAD_NANDF_D2__GPIO2_IO02 0x80000000
MX6QDL_PAD_NANDF_D3__GPIO2_IO03 0x80000000

...}

seems use PAD as GPIO all I need to do is set its config as 0x8000000.

But I got an except here, in the same file:

pinctrl_gpio_keys: gpio_keysgrp {
fsl,pins = <
MX6QDL_PAD_EIM_D29__GPIO3_IO29 0x1b0b0
MX6QDL_PAD_GPIO_4__GPIO1_IO04 0x1b0b0
MX6QDL_PAD_GPIO_5__GPIO1_IO05 0x1b0b0
>;
};

From Documentation/devicetree/bindings/pinctrl/fsl,imx-pinctrl.txt, I got a brief described:

Bits used for CONFIG:
NO_PAD_CTL(1 << 31): indicate this pin does not need config.

Geez, why pinctrl_gpio_keys need to set these gpio configs as 0x1b0b0?

I also check the IMX6QDRM, and found 0x1b0b0 is the default value of IOMUXC_SW_PAD_CTL_PAD_XXX_XXX.

Any suggestion will be appreciated, thanks.

Wally

Re: Does imx.6 device tree gpio config just need to set bit 31 as high?

igorpadykov — Mon, 17 Oct 2016 10:55:39 GMT

Hi Wally

>why pinctrl_gpio_keys need to set these gpio configs as 0x1b0b0?

it could be changed before in bootloader, so linux sets them in some predefined

state.

Best regards
igor
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Re: Does imx.6 device tree gpio config just need to set bit 31 as high?

wallyyeh — Mon, 17 Oct 2016 12:00:18 GMT

Hi, Igorpadykov:

Thankyou, I appreciated your answer. :smileygrin:

You mean pinctrl_gpio_keys will be changed during U-Boot, so I suppose gpios in pinctrl_hog are not changed during U-Boot, is it correct?

Wally

Re: Does imx.6 device tree gpio config just need to set bit 31 as high?

igorpadykov — Tue, 18 Oct 2016 00:05:26 GMT

I meant they can be changed in uboot, so linux sets them in predefined

state for usage with linux drivers

~igor

Re: Does imx.6 device tree gpio config just need to set bit 31 as high?

wallyyeh — Tue, 18 Oct 2016 01:20:07 GMT

Hi, Igor:

igorpadykov 留言:
I meant they can be changed in uboot, so linux sets them in predefined
state for usage with linux drivers

~igor

It sounds reasonable that we should set all gpio in predefined state if we wanna use them.

your answer let me understand that why setting pinctrl_gpio_keys group as 0x1b0b0, but I still can not understand why don't do the same setting to the pinctrl_hog gruop? I think they are under the same purpose - for gpio.

So I think they(pinctrl_gpio_keys and pinctrl_hog) should be different, maybe the input/output is different?

Wally