v4.19.13 snapshot.
diff --git a/arch/riscv/kernel/irq.c b/arch/riscv/kernel/irq.c
new file mode 100644
index 0000000..0cfac48
--- /dev/null
+++ b/arch/riscv/kernel/irq.c
@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ * Copyright (C) 2017 SiFive
+ * Copyright (C) 2018 Christoph Hellwig
+ */
+
+#include <linux/interrupt.h>
+#include <linux/irqchip.h>
+#include <linux/irqdomain.h>
+
+/*
+ * Possible interrupt causes:
+ */
+#define INTERRUPT_CAUSE_SOFTWARE 1
+#define INTERRUPT_CAUSE_TIMER 5
+#define INTERRUPT_CAUSE_EXTERNAL 9
+
+/*
+ * The high order bit of the trap cause register is always set for
+ * interrupts, which allows us to differentiate them from exceptions
+ * quickly. The INTERRUPT_CAUSE_* macros don't contain that bit, so we
+ * need to mask it off.
+ */
+#define INTERRUPT_CAUSE_FLAG (1UL << (__riscv_xlen - 1))
+
+asmlinkage void __irq_entry do_IRQ(struct pt_regs *regs, unsigned long cause)
+{
+ struct pt_regs *old_regs = set_irq_regs(regs);
+
+ irq_enter();
+ switch (cause & ~INTERRUPT_CAUSE_FLAG) {
+ case INTERRUPT_CAUSE_TIMER:
+ riscv_timer_interrupt();
+ break;
+#ifdef CONFIG_SMP
+ case INTERRUPT_CAUSE_SOFTWARE:
+ /*
+ * We only use software interrupts to pass IPIs, so if a non-SMP
+ * system gets one, then we don't know what to do.
+ */
+ riscv_software_interrupt();
+ break;
+#endif
+ case INTERRUPT_CAUSE_EXTERNAL:
+ handle_arch_irq(regs);
+ break;
+ default:
+ panic("unexpected interrupt cause");
+ }
+ irq_exit();
+
+ set_irq_regs(old_regs);
+}
+
+void __init init_IRQ(void)
+{
+ irqchip_init();
+}