Re: [RFC PATCH v2 00/11] Linux RISC-V ACLINT Support

[Anup Patel <anup@brainfault.org>]

Hi Marc,

I have taken the approach of IPI domains (like you suggested) in this series.

What do you think ?

Regards,
Anup

On Fri, Jun 18, 2021 at 6:09 PM Anup Patel <anup.patel@wdc.com> wrote:
>
> Most of the existing RISC-V platforms use SiFive CLINT to provide M-level
> timer and IPI support whereas S-level uses SBI calls for timer and IPI
> support. Also, the SiFive CLINT device is a single device providing both
> timer and IPI functionality so RISC-V platforms can't partially implement
> SiFive CLINT device and provide alternate mechanism for timer and IPI.
>
> The RISC-V Advacned Core Local Interruptor (ACLINT) tries to address the
> limitations of SiFive CLINT by:
> 1) Taking modular approach and defining timer and IPI functionality as
>    separate devices so that RISC-V platforms can include only required
>    devices
> 2) Providing dedicated MMIO device for S-level IPIs so that SBI calls
>    can be avoided for IPIs in Linux RISC-V
> 3) Allowing multiple instances of timer and IPI devices for a
>    multi-socket (or multi-die) NUMA systems
> 4) Being backward compatible to SiFive CLINT so that existing RISC-V
>    platforms stay compliant with RISC-V ACLINT specification
>
> Latest RISC-V ACLINT specification (will be frozen in a month) can be
> found at:
> https://github.com/riscv/riscv-aclint/blob/main/riscv-aclint.adoc
>
> This series adds RISC-V ACLINT support and can be found in riscv_aclint_v2
> branch at:
> https://github.com/avpatel/linux
>
> To test this series, the RISC-V ACLINT support for QEMU and OpenSBI
> can be found in the riscv_aclint_v1 branch at:
> https://github.com/avpatel/qemu
> https://github.com/avpatel/opensbi
>
> Changes since v1:
>  - Added a new PATCH3 to treat IPIs as normal Linux IRQs for RISC-V kernel
>  - New SBI IPI call based irqchip driver in PATCH3 which is only initialized
>    by riscv_ipi_setup() when no Linux IRQ numbers are available for IPIs
>  - Moved DT bindings patches before corresponding driver patches
>  - Implemented ACLINT SWI driver as a irqchip driver in PATCH7
>  - Minor nit fixes pointed by Bin Meng
>
> Anup Patel (11):
>   RISC-V: Clear SIP bit only when using SBI IPI operations
>   RISC-V: Use common print prefix in smp.c
>   RISC-V: Treat IPIs as normal Linux IRQs
>   RISC-V: Allow marking IPIs as suitable for remote FENCEs
>   RISC-V: Use IPIs for remote TLB flush when possible
>   dt-bindings: interrupt-controller: Add ACLINT MSWI and SSWI bindings
>   irqchip: Add ACLINT software interrupt driver
>   RISC-V: Select ACLINT SWI driver for virt machine
>   dt-bindings: timer: Add ACLINT MTIMER bindings
>   clocksource: clint: Add support for ACLINT MTIMER device
>   MAINTAINERS: Add entry for RISC-V ACLINT drivers
>
>  .../riscv,aclint-swi.yaml                     |  82 ++++++
>  .../bindings/timer/riscv,aclint-mtimer.yaml   |  55 ++++
>  MAINTAINERS                                   |   9 +
>  arch/riscv/Kconfig                            |   1 +
>  arch/riscv/Kconfig.socs                       |   1 +
>  arch/riscv/include/asm/sbi.h                  |   2 +
>  arch/riscv/include/asm/smp.h                  |  48 +++-
>  arch/riscv/kernel/Makefile                    |   1 +
>  arch/riscv/kernel/cpu-hotplug.c               |   2 +
>  arch/riscv/kernel/irq.c                       |   1 +
>  arch/riscv/kernel/sbi-ipi.c                   | 223 ++++++++++++++
>  arch/riscv/kernel/sbi.c                       |  15 -
>  arch/riscv/kernel/smp.c                       | 171 +++++------
>  arch/riscv/kernel/smpboot.c                   |   4 +-
>  arch/riscv/mm/tlbflush.c                      |  62 +++-
>  drivers/clocksource/timer-clint.c             |  58 ++--
>  drivers/irqchip/Kconfig                       |  11 +
>  drivers/irqchip/Makefile                      |   1 +
>  drivers/irqchip/irq-aclint-swi.c              | 271 ++++++++++++++++++
>  drivers/irqchip/irq-riscv-intc.c              |  55 ++--
>  20 files changed, 879 insertions(+), 194 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/interrupt-controller/riscv,aclint-swi.yaml
>  create mode 100644 Documentation/devicetree/bindings/timer/riscv,aclint-mtimer.yaml
>  create mode 100644 arch/riscv/kernel/sbi-ipi.c
>  create mode 100644 drivers/irqchip/irq-aclint-swi.c
>
> --
> 2.25.1
>