PREEMPT_RT support for linux-phytec-imx 6.6 on scarthgap

[CMeierSoftware]

Bug: preempt-rt.scc Not Found During do_kernel_metadata — linux-phytec-imx 6.6

Platform: i.MX8MP (phyBOARD-Pollux)
BSP Release: BSP-Yocto-NXP-i.MX8MP-PD24.1.0
Distro: ampliphy-vendor-rt
Kernel recipe: linux-phytec-imx_6.6.23-2.0.0-phy

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Summary

Building phytec-headless-image with distro ampliphy-vendor-rt fails during do_kernel_metadata because the kernel recipe references the feature file preempt-rt.scc without a path prefix.
I asume, the file actually resides at ktypes/preempt-rt/preempt-rt.scc inside the fetched yocto-kernel-cache (kmeta) repository. BitBake cannot resolve the unqualified name and aborts the task.

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Steps to Reproduce

# 1. Fetch the BSP
./phyLinux init -p imx8mp -r BSP-Yocto-NXP-i.MX8MP-PD24.1.0

# 2. Source the environment
source sources/poky/oe-init-build-env build

# 3. Set the distro in build/conf/local.conf
#    DISTRO ?= "ampliphy-vendor-rt"

# 4. Build
bitbake phytec-headless-image

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Error Message

| DEBUG: Using .../meta-ampliphy/recipes-kernel/linux/features/deselect-xen.cfg
| DEBUG: Executing shell function do_kernel_metadata
| NOTE: do_kernel_metadata: for summary/debug, set KCONF_AUDIT_LEVEL > 0
| ERROR: Feature 'preempt-rt.scc' not found, this will cause configuration failures.
| ERROR: Check the SRC_URI for meta-data repositories or directories that may be missing
| ERROR: Set KERNEL_DANGLING_FEATURES_WARN_ONLY to ignore this issue
| WARNING: exit code 1 from a shell command.
ERROR: Task (.../meta-phytec/recipes-kernel/linux/linux-phytec-imx_6.6.23-2.0.0-phy.bb:do_kernel_metadata) failed with exit code '1'

Full build log will be attached.

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Root Cause

linux-phytec-imx_6.6.23-2.0.0-phy.bb appends preempt-rt.scc to KERNEL_FEATURES when preempt-rt is present in DISTRO_FEATURES (ampliphy-vendor-rt.conf sets this):

# linux-phytec-imx_6.6.23-2.0.0-phy.bb (line ~28)
KERNEL_FEATURES:append = " ${@bb.utils.contains("DISTRO_FEATURES", "preempt-rt", "preempt-rt.scc", "", d)}"

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Affected File

sources/meta-phytec/recipes-kernel/linux/linux-phytec-imx_6.6.23-2.0.0-phy.bb

# Broken:
KERNEL_FEATURES:append = " ${@bb.utils.contains("DISTRO_FEATURES", "preempt-rt", "preempt-rt.scc", "", d)}"

# Should be:
KERNEL_FEATURES:append = " ${@bb.utils.contains("DISTRO_FEATURES", "preempt-rt", "ktypes/preempt-rt/preempt-rt.scc", "", d)}"

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Attachments

• Full do_kernel_metadata log Full_log.txt

[smk-embedded]

We currently do not support preempt RT on the PD24 scarthgap branch of the i.MX8M Plus. The last version which was validated in-house was with the 5.10 kernel, as you can see in the release notes for PD23. Currently we have the 5.17 upstream kernel running in the OSADL PREEMPT-RT Testracks for long-term stability:
https://www.osadl.org/Profile-of-system-in-rack-b-slot-5.qa-profile-rbs5.0.html?shadow=1
So fixing the current Yocto receipt is not enough. Also, if you look at the scarthgap branch, following the development of the PD24 stable updates, the preempt-rt feature has been removed, so the error does not trigger. Nevertheless you do not have a solution. We currently are in the process to releasing the 6.12 kernel on walnascar. In the first release there will also be no preempt-rt support included.

I will change this bug into a feature request. Can you review my answer and tell me your preferred solution?

[CMeierSoftware]

Thanks for the update.
For now I’ll stay with the non-RT 24PD BSP. I plan to evaluate PREEMPT_RT/6.12 kernel again once the Walnascar release becomes available.