powerpc/xics: Remove ICS list

We always had only one ICS per machine. Simplify the XICS driver by
removing the ICS list.

The ICS stored in the chip data of the XICS domain becomes useless and
we don't need it anymore to migrate away IRQs from a CPU. This will be
removed in a subsequent patch.
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210701132750.1475580-17-clg@kaod.org

arch/powerpc/sysdev/xics/xics-common.c

@@ -38,7 +38,7 @@ DEFINE_PER_CPU(struct xics_cppr, xics_cppr);
 
 struct irq_domain *xics_host;
 
-static LIST_HEAD(ics_list);
+static struct ics *xics_ics;
 
 void xics_update_irq_servers(void)
 {
@@ -111,12 +111,11 @@ void xics_setup_cpu(void)
 
 void xics_mask_unknown_vec(unsigned int vec)
 {
-	struct ics *ics;
-
 	pr_err("Interrupt 0x%x (real) is invalid, disabling it.\n", vec);
 
-	list_for_each_entry(ics, &ics_list, link)
-		ics->mask_unknown(ics, vec);
+	if (WARN_ON(!xics_ics))
+		return;
+	xics_ics->mask_unknown(xics_ics, vec);
 }
 
 
@@ -198,7 +197,6 @@ void xics_migrate_irqs_away(void)
 		struct irq_chip *chip;
 		long server;
 		unsigned long flags;
-		struct ics *ics;
 
 		/* We can't set affinity on ISA interrupts */
 		if (virq < NR_IRQS_LEGACY)
@@ -219,13 +217,10 @@ void xics_migrate_irqs_away(void)
 		raw_spin_lock_irqsave(&desc->lock, flags);
 
 		/* Locate interrupt server */
-		server = -1;
-		ics = irq_desc_get_chip_data(desc);
-		if (ics)
-			server = ics->get_server(ics, irq);
+		server = xics_ics->get_server(xics_ics, irq);
 		if (server < 0) {
-			printk(KERN_ERR "%s: Can't find server for irq %d\n",
-			       __func__, irq);
+			pr_err("%s: Can't find server for irq %d/%x\n",
+			       __func__, virq, irq);
 			goto unlock;
 		}
 
@@ -307,13 +302,9 @@ int xics_get_irq_server(unsigned int virq, const struct cpumask *cpumask,
 static int xics_host_match(struct irq_domain *h, struct device_node *node,
 			   enum irq_domain_bus_token bus_token)
 {
-	struct ics *ics;
-
-	list_for_each_entry(ics, &ics_list, link)
-		if (ics->host_match(ics, node))
-			return 1;
-
+	if (WARN_ON(!xics_ics))
 		return 0;
+	return xics_ics->host_match(xics_ics, node) ? 1 : 0;
 }
 
 /* Dummies */
@@ -330,8 +321,6 @@ static struct irq_chip xics_ipi_chip = {
 static int xics_host_map(struct irq_domain *h, unsigned int virq,
 			 irq_hw_number_t hw)
 {
-	struct ics *ics;
-
 	pr_devel("xics: map virq %d, hwirq 0x%lx\n", virq, hw);
 
 	/*
@@ -348,12 +337,14 @@ static int xics_host_map(struct irq_domain *h, unsigned int virq,
 		return 0;
 	}
 
-	/* Let the ICS setup the chip data */
-	list_for_each_entry(ics, &ics_list, link)
-		if (ics->map(ics, virq) == 0)
-			return 0;
+	if (WARN_ON(!xics_ics))
+		return -EINVAL;
 
+	/* Let the ICS setup the chip data */
+	if (xics_ics->map(xics_ics, virq))
 		return -EINVAL;
+
+	return 0;
 }
 
 static int xics_host_xlate(struct irq_domain *h, struct device_node *ct,
@@ -427,7 +418,9 @@ static void __init xics_init_host(void)
 
 void __init xics_register_ics(struct ics *ics)
 {
-	list_add(&ics->link, &ics_list);
+	if (WARN_ONCE(xics_ics, "XICS: Source Controller is already defined !"))
+		return;
+	xics_ics = ics;
 }
 
 static void __init xics_get_server_size(void)