New version of T-HEAD C920 implement a fully featured ACLINT[1] device
(This core is used by Sophgo SG2044). This ACLINT device provides a
SSWI field to support fast S-mode IPI. This SSWI device is like the
MSWI device in CLINT/ACLINT, but for S-mode. The only thing is different
from the draft is that the T-HEAD version SSWI needs to write 0 on the
SSWI address to clear the IPI.

Add full support for T-HEAD C900 SSWI device.

[1] https://github.com/riscv/riscv-aclint

Change from v1:
1. patch 2: use computed reg offset to avoid uncessary reg additions
   when setting/clearing irq.
2. patch 2: fix mulitple format issues and improve some comments.
3. patch 2: disable cpu irq when CPU is stopped.

Inochi Amaoto (3):
  dt-bindings: interrupt-controller: Add Sophgo SG2044 ACLINT SSWI
  irqchip: add T-HEAD C900 ACLINT SSWI driver
  riscv: defconfig: Enable T-HEAD C900 ACLINT SSWI drivers

 .../thead,c900-aclint-sswi.yaml               |  58 ++++++
 arch/riscv/configs/defconfig                  |   1 +
 drivers/irqchip/Kconfig                       |  10 ++
 drivers/irqchip/Makefile                      |   1 +
 drivers/irqchip/irq-thead-c900-aclint-sswi.c  | 166 ++++++++++++++++++
 include/linux/cpuhotplug.h                    |   1 +
 6 files changed, 237 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/interrupt-controller/thead,c900-aclint-sswi.yaml
 create mode 100644 drivers/irqchip/irq-thead-c900-aclint-sswi.c

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2.47.0