MIPS: IRQ/IP27: Move IRQ allocation API to platform code.

allocate_irqno, free_irqno and alloc_legacy_irqno are a simple allocator
for interrupt numbers from the days when the numer of interrupts was still
fixed to NR_IRQS.  This was necessary for the SGI IP27 architecture which
with its flexible architecture and possibly large number of interrupts
doesn't easily fit into the old pattern.  These days there are better
alternatives.

Move the allocation code from the arch generic code to the only platform
using it, the SGI IP27 aka Origin 200/2000, Onyx 2.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

2 files changed, 51 insertions, 3 deletions

diff --git a/arch/mips/sgi-ip27/Makefile b/arch/mips/sgi-ip27/Makefile
index da8f6816d346..ab4affa626c7 100644
--- a/arch/mips/sgi-ip27/Makefile
+++ b/arch/mips/sgi-ip27/Makefile
@@ -2,9 +2,9 @@
 # Makefile for the IP27 specific kernel interface routines under Linux.
 #
 
-obj-y	:= ip27-berr.o ip27-irq.o ip27-init.o ip27-klconfig.o ip27-klnuma.o \
-	   ip27-memory.o ip27-nmi.o ip27-reset.o ip27-timer.o ip27-hubio.o \
-	   ip27-xtalk.o
+obj-y	:= ip27-berr.o ip27-irq.o ip27-irqno.o ip27-init.o ip27-klconfig.o \
+	   ip27-klnuma.o ip27-memory.o ip27-nmi.o ip27-reset.o ip27-timer.o \
+	   ip27-hubio.o ip27-xtalk.o
 
 obj-$(CONFIG_EARLY_PRINTK)	+= ip27-console.o
 obj-$(CONFIG_PCI)		+= ip27-irq-pci.o
diff --git a/arch/mips/sgi-ip27/ip27-irqno.c b/arch/mips/sgi-ip27/ip27-irqno.c
new file mode 100644
index 000000000000..957ab58e1c00
--- /dev/null
+++ b/arch/mips/sgi-ip27/ip27-irqno.c
@@ -0,0 +1,48 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+#include <linux/init.h>
+#include <linux/irq.h>
+#include <linux/types.h>
+
+#include <asm/barrier.h>
+
+static DECLARE_BITMAP(irq_map, NR_IRQS);
+
+int allocate_irqno(void)
+{
+	int irq;
+
+again:
+	irq = find_first_zero_bit(irq_map, NR_IRQS);
+
+	if (irq >= NR_IRQS)
+		return -ENOSPC;
+
+	if (test_and_set_bit(irq, irq_map))
+		goto again;
+
+	return irq;
+}
+
+/*
+ * Allocate the 16 legacy interrupts for i8259 devices.	 This happens early
+ * in the kernel initialization so treating allocation failure as BUG() is
+ * ok.
+ */
+void __init alloc_legacy_irqno(void)
+{
+	int i;
+
+	for (i = 0; i <= 16; i++)
+		BUG_ON(test_and_set_bit(i, irq_map));
+}
+
+void free_irqno(unsigned int irq)
+{
+	smp_mb__before_atomic();
+	clear_bit(irq, irq_map);
+	smp_mb__after_atomic();
+}