csky: Add irq_work support

Running work in hardware interrupt context for csky. Implement:
- arch_irq_work_raise()
- arch_irq_work_has_interrupt()

Signed-off-by: Guo Ren <[e-mail]>
Cc: Arnd Bergmann <[e-mail]>

arch/csky/include/asm/irq_work.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __ASM_CSKY_IRQ_WORK_H
+#define __ASM_CSKY_IRQ_WORK_H
+
+static inline bool arch_irq_work_has_interrupt(void)
+{
+	return true;
+}
+extern void arch_irq_work_raise(void);
+#endif /* __ASM_CSKY_IRQ_WORK_H */

arch/csky/kernel/smp.c

···
 #include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/irq.h>
+#include <linux/irq_work.h>
 #include <linux/irqdomain.h>
 #include <linux/of.h>
 #include <linux/sched/task_stack.h>
···
 	IPI_EMPTY,
 	IPI_RESCHEDULE,
 	IPI_CALL_FUNC,
+	IPI_IRQ_WORK,
 	IPI_MAX
 };
 
···
 
 		if (ops & (1 << IPI_CALL_FUNC))
 			generic_smp_call_function_interrupt();
+
+		if (ops & (1 << IPI_IRQ_WORK))
+			irq_work_run();
 
 		BUG_ON((ops >> IPI_MAX) != 0);
 	}
···
 {
 	send_ipi_message(cpumask_of(cpu), IPI_RESCHEDULE);
 }
+
+#ifdef CONFIG_IRQ_WORK
+void arch_irq_work_raise(void)
+{
+	send_ipi_message(cpumask_of(smp_processor_id()), IPI_IRQ_WORK);
+}
+#endif
 
 void __init smp_prepare_boot_cpu(void)
 {