Since the device hierarchy domain was added by commit c98c1822ee13
("irqchip/mips-gic: Add device hierarchy domain"), GIC local interrupts
have been broken.

Users attempting to setup a per-cpu local IRQ, for example the GIC timer
clock events code in drivers/clocksource/mips-gic-timer.c, the
setup_percpu_irq function would refuse with -EINVAL because the GIC
irqchip driver never called irq_set_percpu_devid so the
IRQ_PER_CPU_DEVID flag was never set for the IRQ. This happens because
irq_set_percpu_devid was being called from the gic_irq_domain_map
function which is no longer called.

Doing only that runs into further problems because gic_dev_domain_alloc
set the struct irq_chip for all interrupts, local or shared, to
gic_level_irq_controller despite that only being suitable for shared
interrupts. The typical outcome of this is that gic_level_irq_controller
callback functions are called for local interrupts, and then hwirq
number calculations overflow & the driver ends up attempting to access
some invalid register with an address calculated from an invalid hwirq
number. Best case scenario is that this then leads to a bus error. This
is fixed by abstracting the setup of the hwirq & chip to a new function
gic_setup_dev_chip which is used by both the root GIC IRQ domain & the
device domain.

Finally, decoding local interrupts failed because gic_dev_domain_alloc
only called irq_domain_alloc_irqs_parent for shared interrupts. Local
ones were therefore never associated with hwirqs in the root GIC IRQ
domain and the virq in gic_handle_local_int would always be 0. This is
fixed by calling irq_domain_alloc_irqs_parent unconditionally & having
gic_irq_domain_alloc handle both local & shared interrupts, which is
easy due to the aforementioned abstraction of chip setup into
gic_setup_dev_chip.

This fixes use of the MIPS GIC timer for clock events, which has been
broken since c98c1822ee13 ("irqchip/mips-gic: Add device hierarchy
domain") but hadn't been noticed due to a silent fallback to the MIPS
coprocessor 0 count/compare clock events device.

Fixes: c98c1822ee13 ("irqchip/mips-gic: Add device hierarchy domain")
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Qais Yousef <qsyousef@gmail.com>
Cc: stable@vger.kernel.org
Cc: Marc Zyngier <marc.zyngier@arm.com>
Link: http://lkml.kernel.org/r/20160913165335.31389-1-paul.burton@imgtec.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>