NRF5x: Uninitalized variable in gpio_api leads to wrong configured GPIO.

[supertoast]

Description of defect

The function gpio_apply_config in gpio_api of NRF5x using a variable with uninitalized memory witch leads to wrong configured GPIO. The member skip_gpio_setup is not initalized, so in our case the configuration of the pull up resistor was sometimes not applied.
[Source]

mbed-os/targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF52/gpio_api.c

Line 127 in e4b81f6

nrfx_gpiote_in_config_t cfg;

Target(s) affected by this defect ?

We use a custom board with NRF52832. I think all targets with this MCU are affected.

Toolchain(s) (name and version) displaying this defect ?

GCC for Arm (gcc-arm-none-eabi-9-2019-q4-major)

What version of Mbed-os are you using (tag or sha) ?

mbed-os-5.15.4

What version(s) of tools are you using. List all that apply (E.g. mbed-cli)

mbed-cli 1.10.2

How is this defect reproduced ?

The error occurs randomly because the memory is uninitialized.

[ciarmcom]

Thank you for raising this detailed GitHub issue. I am now notifying our internal issue triagers.
Internal Jira reference: https://jira.arm.com/browse/MBOTRIAGE-2736

[0xc0170]

@supertoast Thanks for the report. Can you send a new pull request fixing the problem?

[supertoast]

Looks like the bug is already fixed.
e9dd602

[0xc0170]

@supertoast that is although on master branch. It might be useful to propagate to 5.15 branch as well? if yes, can you please backport it (send a new pull request) ?

[supertoast]

Done. #13184