irqchip/gic-v2: Reset APRn registers at boot time

Booting a crash kernel while in an interrupt handler is likely
to leave the Active Priority Registers with some state that
is not relevant to the new kernel, and is likely to lead
to erratic behaviours such as interrupts not firing as their
priority is already active.

As a sanity measure, wipe the APRs clean on startup.
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

drivers/irqchip/irq-gic.c

@@ -453,15 +453,26 @@ static u8 gic_get_cpumask(struct gic_chip_data *gic)
 	return mask;
 }
 
+static bool gic_check_gicv2(void __iomem *base)
+{
+	u32 val = readl_relaxed(base + GIC_CPU_IDENT);
+	return (val & 0xff0fff) == 0x02043B;
+}
+
 static void gic_cpu_if_up(struct gic_chip_data *gic)
 {
 	void __iomem *cpu_base = gic_data_cpu_base(gic);
 	u32 bypass = 0;
 	u32 mode = 0;
+	int i;
 
 	if (gic == &gic_data[0] && static_key_true(&supports_deactivate))
 		mode = GIC_CPU_CTRL_EOImodeNS;
 
+	if (gic_check_gicv2(cpu_base))
+		for (i = 0; i < 4; i++)
+			writel_relaxed(0, cpu_base + GIC_CPU_ACTIVEPRIO + i * 4);
+
 	/*
 	* Preserve bypass disable bits to be written back later
 	*/
@@ -1264,12 +1275,6 @@ static int __init gicv2_force_probe_cfg(char *buf)
 }
 early_param("irqchip.gicv2_force_probe", gicv2_force_probe_cfg);
 
-static bool gic_check_gicv2(void __iomem *base)
-{
-	u32 val = readl_relaxed(base + GIC_CPU_IDENT);
-	return (val & 0xff0fff) == 0x02043B;
-}
-
 static bool gic_check_eoimode(struct device_node *node, void __iomem **base)
 {
 	struct resource cpuif_res;