[RFC PATCH v1 00/10] RISC-V ACLINT Support

Anup Patel anup.patel at wdc.com
Sat Jun 12 09:04:12 PDT 2021

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
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:

This series adds RISC-V ACLINT support and can be found in riscv_aclint_v1
branch at:

To test this series, the RISC-V ACLINT support for QEMU and OpenSBI
can be found in the riscv_aclint_v1 branch at:

Anup Patel (10):
  RISC-V: Clear SIP bit only when using SBI IPI operations
  RISC-V: Use common print prefix in smp.c
  RISC-V: Allow more details in IPI operations
  RISC-V: Use IPIs for remote TLB flush when possible
  irqchip: Add ACLINT software interrupt driver
  RISC-V: Select ACLINT SWI driver for virt machine
  clocksource: clint: Add support for ACLINT MTIMER device
  dt-bindings: timer: Add ACLINT MTIMER bindings
  dt-bindings: timer: Add ACLINT MSWI and SSWI bindings
  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.socs                       |   1 +
 arch/riscv/include/asm/smp.h                  |  15 +++
 arch/riscv/kernel/sbi.c                       |  10 +-
 arch/riscv/kernel/smp.c                       |  36 +++++-
 arch/riscv/mm/cacheflush.c                    |   2 +-
 arch/riscv/mm/tlbflush.c                      |  62 +++++++--
 drivers/clocksource/timer-clint.c             |  45 +++++--
 drivers/irqchip/Kconfig                       |  11 ++
 drivers/irqchip/Makefile                      |   1 +
 drivers/irqchip/irq-aclint-swi.c              | 122 ++++++++++++++++++
 13 files changed, 415 insertions(+), 36 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 drivers/irqchip/irq-aclint-swi.c


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