irqchip: armada-370-xp: Mask all interrupts during initialization.

Until now, the irq-armada-370-xp irqchip driver was not masking all
interrupts at initialization. While in most cases this is not a
problem because the bootloader has probably masked all interrupts, it
becomes a problem when you use kexec: you're in kernel A, with many
interrupts enabled, and then kexec into kernel B, without going
through the bootloader. So during the boot process, if an interrupt
occurs while the corresponding driver has not been loaded, you would
get spurious interrupts.

This commit fixes that by ensuring all interrupts are properly masked
when the irqchip driver is initialized. Note that interrupt masking
takes place at two level: at the global level (main_int_base) and at
the per-CPU level (per_cpu_int_base).

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Link: https://lkml.kernel.org/r/1401481098-23326-6-git-send-email-thomas.petazzoni@free-electrons.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

drivers/irqchip/irq-armada-370-xp.c

@@ -334,6 +334,15 @@ static void armada_mpic_send_doorbell(const struct cpumask *mask,
 
 static void armada_xp_mpic_smp_cpu_init(void)
 {
+	u32 control;
+	int nr_irqs, i;
+
+	control = readl(main_int_base + ARMADA_370_XP_INT_CONTROL);
+	nr_irqs = (control >> 2) & 0x3ff;
+
+	for (i = 0; i < nr_irqs; i++)
+		writel(i, per_cpu_int_base + ARMADA_370_XP_INT_SET_MASK_OFFS);
+
 	/* Clear pending IPIs */
 	writel(0, per_cpu_int_base + ARMADA_370_XP_IN_DRBEL_CAUSE_OFFS);
 
@@ -474,7 +483,7 @@ static int __init armada_370_xp_mpic_of_init(struct device_node *node,
 					     struct device_node *parent)
 {
 	struct resource main_int_res, per_cpu_int_res;
-	int parent_irq;
+	int parent_irq, nr_irqs, i;
 	u32 control;
 
 	BUG_ON(of_address_to_resource(node, 0, &main_int_res));
@@ -496,9 +505,13 @@ static int __init armada_370_xp_mpic_of_init(struct device_node *node,
 	BUG_ON(!per_cpu_int_base);
 
 	control = readl(main_int_base + ARMADA_370_XP_INT_CONTROL);
+	nr_irqs = (control >> 2) & 0x3ff;
+
+	for (i = 0; i < nr_irqs; i++)
+		writel(i, main_int_base + ARMADA_370_XP_INT_CLEAR_ENABLE_OFFS);
 
 	armada_370_xp_mpic_domain =
-		irq_domain_add_linear(node, (control >> 2) & 0x3ff,
+		irq_domain_add_linear(node, nr_irqs,
 				&armada_370_xp_mpic_irq_ops, NULL);
 
 	BUG_ON(!armada_370_xp_mpic_domain);