linux-kernel - [PATCH v2 0/6] genirq/irqchip: RISC-V PLIC cleanup and optimization

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Date:   Thu, 16 Jun 2022 01:40:22 -0500
From:   Samuel Holland <samuel@...lland.org>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <maz@...nel.org>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Albert Ou <aou@...s.berkeley.edu>
Cc:     Samuel Holland <samuel@...lland.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Guo Ren <guoren@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King <linux@...linux.org.uk>,
        Wei Xu <xuwei5@...ilicon.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org
Subject: [PATCH v2 0/6] genirq/irqchip: RISC-V PLIC cleanup and optimization

This series removes the splinlocks and cpumask operations from the PLIC
driver's hot path. To do that, it first makes the IRQ affinity mask
behavior more consistent between uniprocessor and SMP configurations.
(The Allwinner D1 is a uniprocessor SoC containing a PLIC.)

As far as I know, using the priority to mask interrupts is an intended
usage and will work on all existing implementations. See [1] for more
discussion.

A further optimization is to take advantage of the fact that multiple
IRQs can be claimed at once. This allows removing the mask operations
for oneshot IRQs -- i.e. the combination of IRQCHIP_ONESHOT_SAFE and
IRQCHIP_EOI_THREADED, which is not currently supported. I will send
this as a separate series, since it makes more invasive changes to the
generic IRQ code.

[1]: https://lore.kernel.org/lkml/2b063917-17c8-0add-fadf-5aa42532fbbf@sholland.org/

Changes in v2:
 - New patch to prevent GENERIC_IRQ_IPI from being selected on !SMP

Samuel Holland (6):
  genirq: GENERIC_IRQ_EFFECTIVE_AFF_MASK depends on SMP
  genirq: GENERIC_IRQ_IPI depends on SMP
  genirq: Refactor accessors to use irq_data_get_affinity_mask
  genirq: Provide an IRQ affinity mask in non-SMP configs
  irqchip/sifive-plic: Make better use of the effective affinity mask
  irqchip/sifive-plic: Separate the enable and mask operations

 arch/arm/mach-hisi/Kconfig        |  2 +-
 drivers/irqchip/Kconfig           | 19 +++++-----
 drivers/irqchip/irq-sifive-plic.c | 61 ++++++++++++++++---------------
 include/linux/irq.h               | 20 ++++++----
 kernel/irq/Kconfig                |  2 +
 5 files changed, 57 insertions(+), 47 deletions(-)

-- 
2.35.1