i.Mx7-ULP unable to set internal pull-ups from u-boot dts

[quentincabrol]

Dear NXP Support Team

We are trying to enable internal pull-ups on PTF0-3 GPIOs in uboot on a i.Mx7-ULP SoC. The idea is to read the values from these GPIOs to determine which fdt file to load for hardware variants (lines should be internally pulled up and the hw version is decided based on external stronger pull-downs to GND). This works on the Linux side (runtime):

After exporting gpio 96-99 in Linux sysfs, the default value is 1 as we expect.

However, the same change in the uboot dts file (arch/arm/dts/imx7ulpea-ucom-kit_v2.dts) doesn't work - reading zeros:

We are sure we booted the correct uboot because we also changed the model in the dts file and it was printed as expected.

We even tried the attached patch in the board file (with and without the dts changes). But still reading 0s as the value:

Did we miss something? We tested that with the ea-5.10.72 bsp branch (variant u-boot from SoM supplier), uboot ea_v2021.04 branch. Many thanks in advance.

Best regards,

[jimmychan]

You may try to set up this in the board .c file in u-boot source code.

e.g.

https://source.codeaurora.org/external/imx/uboot-imx/tree/board/freescale/mx7ulp_evk/mx7ulp_evk.c?h=...

[mt255]

Hi @jimmychan,

Thanks for that, but if you take a closer look into the attached patch file, the same approach is used to access PTF pins.

We did some additional debugging on the NXP i.MX7ULP EVK and realised that only reading of PTA and PTB pins works as expected from u-boot, but reading of PTC, PTD, PTE or PTF pins always yields zeros.

Is this as expected, a bug or simply not supported in u-boot?

Best,
Matija