irqchip/dw-apb-ictl: Refactor priot to introducing hierarchical irq domains

Add the required abstractions that will help introducing hierarchical
domain support to the dw-apb-ictl driver.

No functional change.
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
[maz: commit message, some cleanups]
Signed-off-by: Marc Zyngier <maz@kernel.org>
Tested-by: Haoyu Lv <lvhaoyu@huawei.com>
Link: https://lore.kernel.org/r/20200924071754.4509-3-thunder.leizhen@huawei.com

drivers/irqchip/irq-dw-apb-ictl.c

@@ -26,7 +26,7 @@
 #define APB_INT_FINALSTATUS_H	0x34
 #define APB_INT_BASE_OFFSET	0x04
 
-static void dw_apb_ictl_handler(struct irq_desc *desc)
+static void dw_apb_ictl_handle_irq_cascaded(struct irq_desc *desc)
 {
 	struct irq_domain *d = irq_desc_get_handler_data(desc);
 	struct irq_chip *chip = irq_desc_get_chip(desc);
@@ -43,7 +43,7 @@ static void dw_apb_ictl_handler(struct irq_desc *desc)
 			u32 virq = irq_find_mapping(d, gc->irq_base + hwirq);
 
 			generic_handle_irq(virq);
-			stat &= ~(1 << hwirq);
+			stat &= ~BIT(hwirq);
 		}
 	}
 
@@ -68,17 +68,20 @@ static void dw_apb_ictl_resume(struct irq_data *d)
 static int __init dw_apb_ictl_init(struct device_node *np,
 				   struct device_node *parent)
 {
+	const struct irq_domain_ops *domain_ops;
 	unsigned int clr = IRQ_NOREQUEST | IRQ_NOPROBE | IRQ_NOAUTOEN;
 	struct resource r;
 	struct irq_domain *domain;
 	struct irq_chip_generic *gc;
 	void __iomem *iobase;
-	int ret, nrirqs, irq, i;
+	int ret, nrirqs, parent_irq, i;
 	u32 reg;
 
+	domain_ops = &irq_generic_chip_ops;
+
 	/* Map the parent interrupt for the chained handler */
-	irq = irq_of_parse_and_map(np, 0);
-	if (irq <= 0) {
+	parent_irq = irq_of_parse_and_map(np, 0);
+	if (parent_irq <= 0) {
 		pr_err("%pOF: unable to parse irq\n", np);
 		return -EINVAL;
 	}
@@ -120,8 +123,7 @@ static int __init dw_apb_ictl_init(struct device_node *np,
 	else
 		nrirqs = fls(readl_relaxed(iobase + APB_INT_ENABLE_L));
 
-	domain = irq_domain_add_linear(np, nrirqs,
-				       &irq_generic_chip_ops, NULL);
+	domain = irq_domain_add_linear(np, nrirqs, domain_ops, NULL);
 	if (!domain) {
 		pr_err("%pOF: unable to add irq domain\n", np);
 		ret = -ENOMEM;
@@ -146,7 +148,8 @@ static int __init dw_apb_ictl_init(struct device_node *np,
 		gc->chip_types[0].chip.irq_resume = dw_apb_ictl_resume;
 	}
 
-	irq_set_chained_handler_and_data(irq, dw_apb_ictl_handler, domain);
+	irq_set_chained_handler_and_data(parent_irq,
+				dw_apb_ictl_handle_irq_cascaded, domain);
 
 	return 0;