Linux 6.8 To Drop Old ARM11 MPCore CPU Support
The ARM11 processor cores implementing ARMv6 were significant in their day for adding multi-processor support, SIMD media instructions, and more, but their time is past due on these two decade old processor designs. Queued via SoC.git ahead of the Linux 6.8 merge window is dropping the ARM11MPCore (ARM11 ARMv6K SMP) support.
Arm's ARM11 MPCore block diagram.
Linaro developer Linus Walleij explained with the ARM11MPCore removal:
"This ARM11 SMP configuration was one of the first SMP configurations the ARM kernel supported, but it has the downside of odd DMA handling, odd cache tagging, and often (as of recent) completely broken cache handling on the ARM RealView PB11MPCore test chips. To boot the platform it was necessary to completely disable the cache. When it comes to the EB 11MPCore it is unclear if this ever worked.
These reference designs are now the only ARMv6K SMP platforms.
As only reference designs of purely academic interest remain, and since the special-cased DMA and PMU code is hard to maintain and doesn't really work, it is not really worth our time.
Delete the ARM11MPCore support along with:
- The special DMA quirk CONFIG_DMA_CACHE_RWFO that is only used on ARMv6K SMP, and we are the last ARMV6K system leaving the building and the cache handling is awkward, so good-bye.
- The special PMU handling that was only used by ARM11MPCore."
This goes along with a lot of other cleaning in recent kernel cycles to drop long obsolete hardware support and other very outdated kernel components for hardware that likely no longer exists in the wild, is very broken, or may exist but rather unlikely to be running new upstream kernel releases. For example, Linux 6.7 dropped Intel Itanium support, very old WiFi drivers are being removed, and old PCMCIA drivers have been among the material facing the chopping block. Farewell!
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