irqchip/mips-gic: Separate IPI reservation & usage tracking

irqchip/mips-gic: Separate IPI reservation & usage tracking

Since commit 66dbbf4633ba ("irqchip/mips-gic: Add a IPI hierarchy
domain") introduced the GIC IPI IRQ domain we have tracked both
reservation of interrupts & their use with a single bitmap - ipi_resrv.
If an interrupt is reserved for use as an IPI but not actually in use
then the appropriate bit is set in ipi_resrv. If an interrupt is either
not reserved for use as an IPI or has been allocated as one then the
appropriate bit is clear in ipi_resrv.

Unfortunately this means that checking whether a bit is set in ipi_resrv
to prevent IPI interrupts being allocated for use with a device is
broken, because if the interrupt has been allocated as an IPI first then
its bit will be clear.

Fix this by separating the tracking of IPI reservation & usage,
introducing a separate ipi_available bitmap for the latter. This means
that ipi_resrv will now always have bits set corresponding to all
interrupts reserved for use as IPIs, whether or not they have been
allocated yet, and therefore that checking it when allocating device
interrupts works as expected.

Fixes: 66dbbf4633ba ("irqchip/mips-gic: Add a IPI hierarchy domain")
Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Signed-off-by: Matt Redfearn <matt.redfearn@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Link: http://lkml.kernel.org/r/1492679256-14513-2-git-send-email-matt.redfearn@imgtec.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>