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RISC-V distinguishes between memory accesses and device I/O and uses FENCE
instruction to order them as viewed by other RISC-V harts and external
devices or coprocessors. The FENCE instruction can order any combination of
device input(I), device output(O), memory reads(R) and memory
writes(W). For example, 'fence w, o' is used to ensure all memory writes
from instructions preceding the FENCE instruction appear earlier in the
global memory order than device output writes from instructions after the
FENCE instruction.
RISC-V issues IPIs by writing to the IMSIC/ACLINT MMIO registers, which is
regarded as device output operation. However, the existing implementation
of the IMSIC/ACLINT drivers issue the IPI via writel_relaxed(), which does
not guarantee the order of device output operation and preceding memory
writes. As a consequence the hart receiving the IPI might not observe the
IPI related data.
Fix this by replacing writel_relaxed() with writel() when issuing IPIs,
which uses 'fence w, o' to ensure all previous writes made by the current
hart are visible to other harts before they receive the IPI.
Signed-off-by: Xu Lu <luxu.kernel@bytedance.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250127093846.98625-1-luxu.kernel@bytedance.com
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RISC-V IMSIC interrupt controller provides IPI and MSI support.
Currently, DT based drivers setup the IPI feature early during boot but
defer setting up the MSI functionality. However, in ACPI systems, PCI
subsystem is probed early and assume MSI controller is already setup.
Hence, both IPI and MSI features need to be initialized early itself.
Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://patch.msgid.link/20240812005929.113499-16-sunilvl@ventanamicro.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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There was a semantic conflict between 21a8f8a0eb35 ("irqchip: Add RISC-V
incoming MSI controller early driver") and dc892fb44322 ("riscv: Use
IPIs for remote cache/TLB flushes by default") due to an API change.
This manifests as a build failure post-merge.
Reported-by: Tomasz Jeznach <tjeznach@rivosinc.com>
Link: https://lore.kernel.org/all/mhng-10b71228-cf3e-42ca-9abf-5464b15093f1@palmer-ri-x1c9/
Fixes: 0bfbc914d943 ("Merge tag 'riscv-for-linus-6.10-mw1' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux")
Reviewed-by: Anup Patel <anup@brainfault.org>
Link: https://lore.kernel.org/r/20240522184953.28531-3-palmer@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
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The RISC-V advanced interrupt architecture (AIA) specification
defines a new MSI controller called incoming message signalled
interrupt controller (IMSIC) which manages MSI on per-HART (or
per-CPU) basis. It also supports IPIs as software injected MSIs.
(For more details refer https://github.com/riscv/riscv-aia)
Add an early irqchip driver for RISC-V IMSIC which sets up the
IMSIC state and provide IPIs.
Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Link: https://lore.kernel.org/r/20240307140307.646078-3-apatel@ventanamicro.com
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