The nitrogen6x machine config also supports other machines according to the comment block inside the .conf file:

# Note that this machine configuration also supports the SABRE Lite
# reference design and the Nitrogen6X-SOM.
#
# By default, this machine will build for the standard Quad-Core, 1GB
# option.
#
# To build U-Boot for other CPU or memory combinations, you can set
# the UBOOT_MACHINE variable in your local.conf according to the
# following table:
#
# Processor           Memory    Configuration
# --------------      ------    --------------------
# i.MX6Quad/Dual        1GB     nitrogen6q_config
# i.MX6Quad/Dual        2GB     nitrogen6q2g_config
# i.MX6Quad/Dual        4GB     nitrogen6_max_config
# i.MX6Dual-Lite        1GB     nitrogen6dl_config
# i.MX6Dual-Lite        2GB     nitrogen6dl2g_config
# i.MX6Solo           512MB     nitrogen6s_config
# i.MX6Solo             1GB     nitrogen6s1g_config

This is the reason for this line in the config:

MACHINEOVERRIDES =. "mx6:mx6dl:mx6q:"

This is a problem, since the features between the different i.MX6 SoC variants to differ. In particular, imxpxp is enabled because of this, even though my nitrogen6x - which has an i.MX6 Quad - has no PxP support. As a result, software whose recipes test for imxpxp presence incorrectly have their PxP features enabled. This is especially bad if it affects ptest packages, which then fail.

I now wonder what to do here. Split nitrogen6x.conf into multiple individual recipes? Or selectively remove machineoverrides somehow?