ARM: orion: provide C-style interrupt handler for MULTI_IRQ_HANDLER

DT-enabled Marvell Kirkwood and Dove SoCs make use of an irqchip
driver. As expected for irqchip drivers, it uses a C-style
interrupt handler and therefore selects MULTI_IRQ_HANDLER.

Now, compiling a kernel with both non-DT and DT support enabled,
selecting MULTI_IRQ_HANDLER will break ASM irq handler used by
non-DT boards.

Therefore, we provide a C-style irq handler even for non-DT boards,
if MULTI_IRQ_HANDLER is set. By installing the C-style irq handler
in orion_irq_init this is transparent to all non-DT board files.

While the regression report was filed on Marvell Kirkwood, also
Marvell Dove non-DT boards are affected and fixed by this patch.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Tested-by: Ian Campbell <ijc@hellion.org.uk>
Reported-by: Ian Campbell <ijc@hellion.org.uk>
Cc: <stable@vger.kernel.org> # v3.12+
Fixes: 2326f04321a9 ("ARM: kirkwood: convert to DT irqchip and clocksource")
Fixes: f07d73e33d0e ("ARM: dove: convert to DT irqchip and clocksource")
Acked-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

arch/arm/plat-orion/irq.c

@@ -15,8 +15,51 @@
 #include <linux/io.h>
 #include <linux/of_address.h>
 #include <linux/of_irq.h>
+#include <asm/exception.h>
 #include <plat/irq.h>
 #include <plat/orion-gpio.h>
+#include <mach/bridge-regs.h>
+
+#ifdef CONFIG_MULTI_IRQ_HANDLER
+/*
+ * Compiling with both non-DT and DT support enabled, will
+ * break asm irq handler used by non-DT boards. Therefore,
+ * we provide a C-style irq handler even for non-DT boards,
+ * if MULTI_IRQ_HANDLER is set.
+ *
+ * Notes:
+ * - this is prepared for Kirkwood and Dove only, update
+ *   accordingly if you add Orion5x or MV78x00.
+ * - Orion5x uses different macro names and has only one
+ *   set of CAUSE/MASK registers.
+ * - MV78x00 uses the same macro names but has a third
+ *   set of CAUSE/MASK registers.
+ *
+ */
+
+static void __iomem *orion_irq_base = IRQ_VIRT_BASE;
+
+asmlinkage void
+__exception_irq_entry orion_legacy_handle_irq(struct pt_regs *regs)
+{
+	u32 stat;
+
+	stat = readl_relaxed(orion_irq_base + IRQ_CAUSE_LOW_OFF);
+	stat &= readl_relaxed(orion_irq_base + IRQ_MASK_LOW_OFF);
+	if (stat) {
+		unsigned int hwirq = __fls(stat);
+		handle_IRQ(hwirq, regs);
+		return;
+	}
+	stat = readl_relaxed(orion_irq_base + IRQ_CAUSE_HIGH_OFF);
+	stat &= readl_relaxed(orion_irq_base + IRQ_MASK_HIGH_OFF);
+	if (stat) {
+		unsigned int hwirq = 32 + __fls(stat);
+		handle_IRQ(hwirq, regs);
+		return;
+	}
+}
+#endif
 
 void __init orion_irq_init(unsigned int irq_start, void __iomem *maskaddr)
 {
@@ -35,6 +78,10 @@ void __init orion_irq_init(unsigned int irq_start, void __iomem *maskaddr)
 	ct->chip.irq_unmask = irq_gc_mask_set_bit;
 	irq_setup_generic_chip(gc, IRQ_MSK(32), IRQ_GC_INIT_MASK_CACHE,
 			       IRQ_NOREQUEST, IRQ_LEVEL | IRQ_NOPROBE);
+
+#ifdef CONFIG_MULTI_IRQ_HANDLER
+	set_handle_irq(orion_legacy_handle_irq);
+#endif
 }
 
 #ifdef CONFIG_OF