New version of T-HEAD C920[1] implement a fully featured ACLINT 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.

Add full support for T-HEAD C900 SSWI device.

[1] https://www.xrvm.com/product/xuantie/C920

Changed 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.

Changed from v2:
1. patch 2: add SXSTATUS.CLINTEE check for T-HEAD cores.
2. patch 2: add select GENERIC_IRQ_IPI_MUX in Kconfig

Changed from v3:
1. patch 2: add SMP depends in Kconfig

Changed from v4:
1. patch 1/2: update the description to mark the device is T-HEAD specific

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                       |  12 ++
 drivers/irqchip/Makefile                      |   1 +
 drivers/irqchip/irq-thead-c900-aclint-sswi.c  | 176 ++++++++++++++++++
 include/linux/cpuhotplug.h                    |   1 +
 6 files changed, 249 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