Messages in this thread |  | | From | Caleb James DeLisle <> | | Subject | [PATCH v2 0/2] irqchip/econet-en751221: Support MIPS 34Kc VEIC mode | | Date | Thu, 30 Apr 2026 15:08:07 +0000 |
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MIPS 34Kc and 1004Kc have a Vectored External Interrupt mode, where CPU interrupts are re-routed to the external interrupt controller, which prioritizes them, renumbers them, and integrates them with its own, creating a flat interrupt table.
This bypasses the CPU interrupt controller entirely, which is not ideal for modern Linux which formalizes the interrupt hierarchy. The 1004Kc standardized the interrupt controller (MIPS_GIC) so it can be viewed as "part of the CPU" and it's tolerable for it to be more closely coupled to arch/mips/* than a typical interrupt controller driver.
The 34Kc supports VEIC mode, but the interrupt controller is not standardized, so it's different per-SoC. This creates a challenge of writing a reasonably modular driver, given hardware that actually does take over the interrupt hierarchy.
Ordinarily we wouldn't bother with VEIC on the 34Kc but it is required for MIPS_MT_SMP, so without it you get a single thread processor. The only other 34Kc device which has an in-tree DTS file is realtek,rtl9302-soc, in OpenWrt there is this, realtek,rtl839x-soc, and lantiq,xway. Of these, the realtek,rtl839x-soc has multi-thread support via an out-of-tree patch to its interrupt controller, and the lantiq is not 34Kc compliant in that it lacks the VEIC cpu flag, causing linux to fall back on legacy interrupts despite CPU_MIPSR2_IRQ_EI being set.
This patchset aims to tackle this challenge in a way that is most likely generalizable to other 34Kc interrupt controllers which are facing the same problem.
Changes from v1: * Address notes from Thomas Gleixner (Thank you very much!) * Additional info in cover letter regarding lantiq,xway * v1: https://lore.kernel.org/linux-mips/20260425123531.270548-1-cjd@cjdns.fr/
Caleb James DeLisle (2): dt-bindings: interrupt-controller: econet: Add CPU interrupt mapping irqchip/econet-en751221: Support MIPS 34Kc VEIC mode
.../econet,en751221-intc.yaml | 20 ++ drivers/irqchip/irq-econet-en751221.c | 176 +++++++++++++++++- 2 files changed, 193 insertions(+), 3 deletions(-)
base-commit: e8be82c2d77ec1bb0148406e54b105028a83537e -- 2.39.5
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