[RFC PATCH v3 00/11] Linux RISC-V ACLINT Support

[Anup Patel]

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 (to be frozen soon) 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 the
riscv_aclint_v3 branch at:
https://github.com/avpatel/linux

To test this series, the RISC-V ACLINT support for QEMU can be found
in the riscv_aclint_v3 branch at:
https://github.com/avpatel/qemu

Changes since v2:
 - Addresed Rob's comments on [M|S]SWI DT bindings
 - Dropped PATCH2 because it was not a required change
 - Addressed Marc's comments on ACLINT SWI driver added by PATCH7
 - Added a separate PATCH6 to update SiFive CLINT DT bindings

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: 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
  dt-bindings: timer: Update SiFive CLINT bindings for IPI support
  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                     |  95 +++++++
 .../bindings/timer/riscv,aclint-mtimer.yaml   |  70 +++++
 .../bindings/timer/sifive,clint.yaml          |  20 +-
 MAINTAINERS                                   |   9 +
 arch/riscv/Kconfig                            |   1 +
 arch/riscv/Kconfig.socs                       |   1 +
 arch/riscv/boot/dts/canaan/k210.dtsi          |   2 +
 .../boot/dts/microchip/microchip-mpfs.dtsi    |   2 +
 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                   | 215 ++++++++++++++
 arch/riscv/kernel/sbi.c                       |  15 -
 arch/riscv/kernel/smp.c                       | 172 ++++++------
 arch/riscv/kernel/smpboot.c                   |   4 +-
 arch/riscv/mm/tlbflush.c                      |  91 ++++--
 drivers/clocksource/timer-clint.c             |  69 +++--
 drivers/irqchip/Kconfig                       |   9 +
 drivers/irqchip/Makefile                      |   1 +
 drivers/irqchip/irq-riscv-aclint-swi.c        | 265 ++++++++++++++++++
 drivers/irqchip/irq-riscv-intc.c              |  55 ++--
 23 files changed, 946 insertions(+), 204 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-riscv-aclint-swi.c

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2.25.1