Messages in this thread | | | Date | Wed, 27 May 2020 11:47:08 -0700 (PDT) | Subject | Re: [PATCH v5 0/6] New RISC-V Local Interrupt Controller Driver | From | Palmer Dabbelt <> |
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On Thu, 21 May 2020 06:32:55 PDT (-0700), Anup Patel wrote: > This patchset provides a new RISC-V Local Interrupt Controller Driver > for managing per-CPU local interrupts. The overall approach is inspired > from the way per-CPU local interrupts are handled by Linux ARM64 and > ARM GICv3 driver. > > Few advantages of this new driver over previous one are: > 1. All local interrupts are registered as per-CPU interrupts > 2. The RISC-V timer driver can register timer interrupt handler > using kernel irq subsystem without relying on arch/riscv to > explicitly call it's interrupt handler > 3. The KVM RISC-V can use this driver to implement interrupt > handler for per-HART guest external interrupt defined by > the RISC-V H-Extension > 4. In future, we can develop drivers for devices with per-HART > interrupts without changing arch code or this driver (example, > CLINT timer driver for RISC-V M-mode kernel) > > With this patchset, output of "cat /proc/interrupts" looks as follows: > CPU0 CPU1 CPU2 CPU3 > 2: 379 0 0 0 SiFive PLIC 10 ttyS0 > 3: 591 0 0 0 SiFive PLIC 8 virtio0 > 5: 5079 10821 8435 12984 RISC-V INTC 5 riscv-timer > IPI0: 2045 2537 891 870 Rescheduling interrupts > IPI1: 9 269 91 168 Function call interrupts > IPI2: 0 0 0 0 CPU stop interrupts > > The patchset is based up Linux-5.7-rc6 and can be found at riscv_intc_v5 > branch of: https://github.com/avpatel/linux.git > > This series is tested on: > 1. QEMU RV64 virt machine using Linux RISC-V S-mode > 2. QEMU RV32 virt machine using Linux RISC-V S-mode > 3. QEMU RV64 virt machine using Linux RISC-V M-mode (i.e. NoMMU) > > Changes since v4: > - Rebased to Linux-5.7-rc6 and multi-PLIC improvement patches > - Added separate patch to force select RISCV_INTC for CONFIG_RISCV > - Fixed the driver for Linux RISC-V NoMMU > > Changes since v3: > - Rebased to Linux-5.6-rc5 and Atish's PLIC patches > - Added separate patch to rename and move plic_find_hart_id() > to arch directory > - Use riscv_of_parent_hartid() in riscv_intc_init() instead of > atomic counter > > Changes since v2: > - Dropped PATCH2 since it was merged long-time back > - Rebased series from Linux-4.19-rc2 to Linux-5.6-rc2 > > Changes since v1: > - Removed changes related to puggable IPI triggering > - Separate patch for self-contained IPI handling routine > - Removed patch for GENERIC_IRQ kconfig options > - Added patch to remove do_IRQ() function > - Rebased upon Atish's SMP patches > > Anup Patel (6): > RISC-V: self-contained IPI handling routine > RISC-V: Rename and move plic_find_hart_id() to arch directory > irqchip: RISC-V per-HART local interrupt controller driver > clocksource/drivers/timer-riscv: Use per-CPU timer interrupt > RISC-V: Remove do_IRQ() function > RISC-V: Force select RISCV_INTC for CONFIG_RISCV > > arch/riscv/Kconfig | 2 + > arch/riscv/include/asm/irq.h | 5 - > arch/riscv/include/asm/processor.h | 1 + > arch/riscv/include/asm/smp.h | 3 + > arch/riscv/kernel/cpu.c | 16 +++ > arch/riscv/kernel/entry.S | 4 +- > arch/riscv/kernel/irq.c | 33 +----- > arch/riscv/kernel/smp.c | 11 +- > arch/riscv/kernel/traps.c | 2 - > drivers/clocksource/timer-riscv.c | 30 ++++- > drivers/irqchip/Kconfig | 13 +++ > drivers/irqchip/Makefile | 1 + > drivers/irqchip/irq-riscv-intc.c | 150 +++++++++++++++++++++++++ > drivers/irqchip/irq-sifive-plic.c | 52 +++++---- > include/linux/cpuhotplug.h | 1 + > include/linux/irqchip/irq-riscv-intc.h | 20 ++++ > 16 files changed, 280 insertions(+), 64 deletions(-) > create mode 100644 drivers/irqchip/irq-riscv-intc.c > create mode 100644 include/linux/irqchip/irq-riscv-intc.h
So I read through this a bit, and while I haven't gone through every line of code I'm somewhat inclined toward taking it.
During the original RISC-V port submission we went back and forth between having this first-level interrupt controller in arch/riscv/ vs drivers/irqchip/. The original deciding factor was that the ISA mandated the interrupt controller, but as that's proving to be less and less the case every day (with the CLIC and M-mode Linux) it certainly seem sane to move all our interrupt controller drivers out of arch/riscv/.
This is certainly a step in the right direction, and it handles some of the more glaring issues (iscv_timer_interrupt and lacking IRQs for the CLINT). I think we should just go ahead and merge it, even though there might be some more refactoring to do when we eventually end up with another interrupt controller.
I think it's best if this all goes in through a single tree, as it seems more work than it's worth to split it up. I'm happy to take it through my tree if that's OK with the irqchip folks?
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