irqchip/sifive-plic: Parse number of interrupts and contexts early in plic_probe()

The SiFive PLIC driver needs to know the number of interrupts and contexts
to complete initialization. Parse these details early in plic_probe() to
avoid unnecessary memory allocations and register mappings if these details
are not available.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20240222094006.1030709-7-apatel@ventanamicro.com

Author: avpatel

drivers/irqchip/irq-sifive-plic.c

@@ -417,6 +417,34 @@ static const struct of_device_id plic_match[] = {
 	{}
 };
 
+static int plic_parse_nr_irqs_and_contexts(struct platform_device *pdev,
+					   u32 *nr_irqs, u32 *nr_contexts)
+{
+	struct device *dev = &pdev->dev;
+	int rc;
+
+	/*
+	 * Currently, only OF fwnode is supported so extend this
+	 * function for ACPI support.
+	 */
+	if (!is_of_node(dev->fwnode))
+		return -EINVAL;
+
+	rc = of_property_read_u32(to_of_node(dev->fwnode), "riscv,ndev", nr_irqs);
+	if (rc) {
+		dev_err(dev, "riscv,ndev property not available\n");
+		return rc;
+	}
+
+	*nr_contexts = of_irq_count(to_of_node(dev->fwnode));
+	if (WARN_ON(!(*nr_contexts))) {
+		dev_err(dev, "no PLIC context available\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int plic_parse_context_parent(struct platform_device *pdev, u32 context,
 				     u32 *parent_hwirq, int *parent_cpu)
 {
@@ -465,31 +493,26 @@ static int plic_probe(struct platform_device *pdev)
 			plic_quirks = (unsigned long)id->data;
 	}
 
+	error = plic_parse_nr_irqs_and_contexts(pdev, &nr_irqs, &nr_contexts);
+	if (error)
+		return error;
+
 	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;
 
 	priv->dev = dev;
 	priv->plic_quirks = plic_quirks;
+	priv->nr_irqs = nr_irqs;
 
 	priv->regs = devm_platform_ioremap_resource(pdev, 0);
 	if (WARN_ON(!priv->regs))
 		return -EIO;
 
-	of_property_read_u32(to_of_node(dev->fwnode), "riscv,ndev", &nr_irqs);
-	if (WARN_ON(!nr_irqs))
-		return -EINVAL;
-
-	priv->nr_irqs = nr_irqs;
-
 	priv->prio_save = devm_bitmap_zalloc(dev, nr_irqs, GFP_KERNEL);
 	if (!priv->prio_save)
 		return -ENOMEM;
 
-	nr_contexts = of_irq_count(to_of_node(dev->fwnode));
-	if (WARN_ON(!nr_contexts))
-		return -EINVAL;
-
 	for (i = 0; i < nr_contexts; i++) {
 		error = plic_parse_context_parent(pdev, i, &parent_hwirq, &cpu);
 		if (error) {