irqchip/armada-370-xp: Do not touch IPI registers on platforms without IPI

On platforms where IPI is not available in the MPIC, the IPI registers
instead represent an additional set of MSI interrupt registers (currently
unused by the driver).

Do not touch these registers on platforms where IPI is not available in the
MPIC.

[ Marek: refactored, changed commit message ]
Signed-off-by: Pali Rohár <pali@kernel.org>
Signed-off-by: Marek Behún <kabel@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>

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

@@ -502,6 +502,9 @@ static void armada_xp_mpic_smp_cpu_init(void)
 	for (i = 0; i < nr_irqs; i++)
 		writel(i, per_cpu_int_base + ARMADA_370_XP_INT_SET_MASK_OFFS);
 
+	if (!is_ipi_available())
+		return;
+
 	/* Disable all IPIs */
 	writel(0, per_cpu_int_base + ARMADA_370_XP_IN_DRBEL_MSK_OFFS);
 
@@ -752,7 +755,7 @@ static void armada_370_xp_mpic_resume(void)
 	/* Reconfigure doorbells for IPIs and MSIs */
 	writel(doorbell_mask_reg,
 	       per_cpu_int_base + ARMADA_370_XP_IN_DRBEL_MSK_OFFS);
-	if (doorbell_mask_reg & IPI_DOORBELL_MASK)
+	if (is_ipi_available() && (doorbell_mask_reg & IPI_DOORBELL_MASK))
 		writel(0, per_cpu_int_base + ARMADA_370_XP_INT_CLEAR_MASK_OFFS);
 	if (doorbell_mask_reg & PCI_MSI_DOORBELL_MASK)
 		writel(1, per_cpu_int_base + ARMADA_370_XP_INT_CLEAR_MASK_OFFS);
@@ -803,13 +806,18 @@ static int __init armada_370_xp_mpic_of_init(struct device_node *node,
 	BUG_ON(!armada_370_xp_mpic_domain);
 	irq_domain_update_bus_token(armada_370_xp_mpic_domain, DOMAIN_BUS_WIRED);
 
+	/*
+	 * Initialize parent_irq before calling any other functions, since it is
+	 * used to distinguish between IPI and non-IPI platforms.
+	 */
+	parent_irq = irq_of_parse_and_map(node, 0);
+
 	/* Setup for the boot CPU */
 	armada_xp_mpic_perf_init();
 	armada_xp_mpic_smp_cpu_init();
 
 	armada_370_xp_msi_init(node, main_int_res.start);
 
-	parent_irq = irq_of_parse_and_map(node, 0);
 	if (parent_irq <= 0) {
 		irq_set_default_host(armada_370_xp_mpic_domain);
 		set_handle_irq(armada_370_xp_handle_irq);