SION bit not working on iMX6 ULL SNVS_TAMPER pads

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SION bit not working on iMX6 ULL SNVS_TAMPER pads

Contributor IV

Hi all,

We have been using a custom board designed for iMX6 UL processor and we recently decided to switch to ULL processor on the same board. There wasn't any trouble with the transition. Now however, I've noticed this issue and can't seem to solve it.

We are using some SNVS_TAMPER pads as GPIO configured as outputs. In addition, we are reading the actual values on those output pins. I'm aware that SION bit is needed to be activated for that purpose. It works correctly with UL processor, but not with ULL processor it seems.

Below is the device-tree configuration of those pins for ULL processor:



&iomuxc_snvs {
	pinctrl-names = "default_snvs";
	pinctrl-0 = <&pinctrl_gpios_2>;
	imx6ul-evk {
		pinctrl_gpios_2: gpiosgrp-2 {
			fsl,pins = <
				MX6ULL_PAD_SNVS_TAMPER5__GPIO5_IO05  0x400120b9 /* DOUT2 */
				MX6ULL_PAD_SNVS_TAMPER1__GPIO5_IO01  0x400120b9 /* DOUT3 */
				MX6ULL_PAD_SNVS_TAMPER4__GPIO5_IO04  0x400120b9 /* DOUT4 */

&iomuxc {
	pinctrl-names = "default";
	pinctrl-0 = <&pinctrl_gpios>;
	imx6ul-evk {
		pinctrl_gpios: gpiosgrp {
			fsl,pins = <
				MX6UL_PAD_NAND_WP_B__GPIO4_IO11		0x400120b9 /* DOUT1 */




As you can see, SION bit is set for all of the pins. The outputs are working correctly, meaning I can set them high/low. But when I try to read the actual value via sysfs, it is always a "1".

We use another output from a different pad (NAND_WP_B, as can be seen above) and there is no problem with that. This problem seems only related to SNVS_TAMPER pads in ULL processor.

Kernel version: 4.1.38-rt45-fslc+gee67fc7

Processor part: MCIMX6Y2CVM08AB

What am I missing here? How can I read back values on SNVS_TAMPER output pins?

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2 Replies

NXP TechSupport
NXP TechSupport

Hi durmu_kurtulu


could you try to reproduce issue on NXP i.MX6ULL EVK reference board with official

linux release from repository:


Best regards

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Contributor IV

Hi igor,

Unfortunately, I don't have access to i.MX6ULL EVK reference board. However, I will try to adapt the latest kernel release to our board and post the result.


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