void arc_init_IRQ()

in kernel/intc-arcv2.c [29:97]

• 40 lines of code
• 4 McCabe index (conditional complexity)

void arc_init_IRQ(void)
{
	unsigned int tmp, irq_prio, i;
	struct bcr_irq_arcv2 irq_bcr;

	struct aux_irq_ctrl {
#ifdef CONFIG_CPU_BIG_ENDIAN
		unsigned int res3:18, save_idx_regs:1, res2:1,
			     save_u_to_u:1, save_lp_regs:1, save_blink:1,
			     res:4, save_nr_gpr_pairs:5;
#else
		unsigned int save_nr_gpr_pairs:5, res:4,
			     save_blink:1, save_lp_regs:1, save_u_to_u:1,
			     res2:1, save_idx_regs:1, res3:18;
#endif
	} ictrl;

	*(unsigned int *)&ictrl = 0;

#ifndef CONFIG_ARC_IRQ_NO_AUTOSAVE
	ictrl.save_nr_gpr_pairs = 6;	/* r0 to r11 (r12 saved manually) */
	ictrl.save_blink = 1;
	ictrl.save_lp_regs = 1;		/* LP_COUNT, LP_START, LP_END */
	ictrl.save_u_to_u = 0;		/* user ctxt saved on kernel stack */
	ictrl.save_idx_regs = 1;	/* JLI, LDI, EI */
#endif

	WRITE_AUX(AUX_IRQ_CTRL, ictrl);

	/*
	 * ARCv2 core intc provides multiple interrupt priorities (upto 16).
	 * Typical builds though have only two levels (0-high, 1-low)
	 * Linux by default uses lower prio 1 for most irqs, reserving 0 for
	 * NMI style interrupts in future (say perf)
	 */

	READ_BCR(ARC_REG_IRQ_BCR, irq_bcr);

	irq_prio = irq_bcr.prio;	/* Encoded as N-1 for N levels */
	pr_info("archs-intc\t: %d priority levels (default %d)%s\n",
		irq_prio + 1, ARCV2_IRQ_DEF_PRIO,
		irq_bcr.firq ? " FIRQ (not used)":"");

	/*
	 * Set a default priority for all available interrupts to prevent
	 * switching of register banks if Fast IRQ and multiple register banks
	 * are supported by CPU.
	 * Also disable private-per-core IRQ lines so faulty external HW won't
	 * trigger interrupt that kernel is not ready to handle.
	 */
	for (i = NR_EXCEPTIONS; i < irq_bcr.irqs + NR_EXCEPTIONS; i++) {
		write_aux_reg(AUX_IRQ_SELECT, i);
		write_aux_reg(AUX_IRQ_PRIORITY, ARCV2_IRQ_DEF_PRIO);

		/*
		 * Only mask cpu private IRQs here.
		 * "common" interrupts are masked at IDU, otherwise it would
		 * need to be unmasked at each cpu, with IPIs
		 */
		if (i < FIRST_EXT_IRQ)
			write_aux_reg(AUX_IRQ_ENABLE, 0);
	}

	/* setup status32, don't enable intr yet as kernel doesn't want */
	tmp = read_aux_reg(ARC_REG_STATUS32);
	tmp |= ARCV2_IRQ_DEF_PRIO << 1;
	tmp &= ~STATUS_IE_MASK;
	asm volatile("kflag %0	\n"::"r"(tmp));
}