irqchip/mips-cpu: Set IPI domain parent chip

Since commit 55567976 ("genirq/irqdomain: Allow partial trimming of
irq_data hierarchy") the irq_data chain is valided.

The irq_domain_trim_hierarchy() function doesn't consider the irq + ipi
domain hierarchy as valid, since the ipi domain has the irq domain set
as parent, but the parent domain has no chip set. Hence the boot ends in
a kernel panic.

Set the chip for the parent domain as it is done in the mips gic irq
driver, to have a valid irq_data chain.

Fixes: 3838a547 ("irqchip: mips-cpu: Introduce IPI IRQ domain support")
Cc: <stable@vger.kernel.org> # v5.10+
Signed-off-by: Mathias Kresin <dev@kresin.me>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210107213603.1637781-1-dev@kresin.me

drivers/irqchip/irq-mips-cpu.c

@@ -197,6 +197,13 @@ static int mips_cpu_ipi_alloc(struct irq_domain *domain, unsigned int virq,
 		if (ret)
 			return ret;
 
+		ret = irq_domain_set_hwirq_and_chip(domain->parent, virq + i, hwirq,
+						    &mips_mt_cpu_irq_controller,
+						    NULL);
+
+		if (ret)
+			return ret;
+
 		ret = irq_set_irq_type(virq + i, IRQ_TYPE_LEVEL_HIGH);
 		if (ret)
 			return ret;