PCI: xgene-msi: Restructure handler setup/teardown

Another utterly pointless aspect of the xgene-msi driver is that
it is built around CPU hotplug. Which is quite amusing since this
is one of the few arm64 platforms that, by construction, cannot
do CPU hotplug in a supported way (no EL3, no PSCI, no luck).

Drop the CPU hotplug nonsense and just setup the IRQs and handlers
in a less overdesigned way, grouping things more logically in the
process.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20250708173404.1278635-13-maz@kernel.org

Author: Marc Zyngier

drivers/pci/controller/pci-xgene-msi.c

@@ -231,12 +231,6 @@ static int xgene_allocate_domains(struct device_node *node,
 	return msi->inner_domain ? 0 : -ENOMEM;
 }
 
-static void xgene_free_domains(struct xgene_msi *msi)
-{
-	if (msi->inner_domain)
-		irq_domain_remove(msi->inner_domain);
-}
-
 static int xgene_msi_init_allocator(struct device *dev)
 {
 	xgene_msi_ctrl->bitmap = devm_bitmap_zalloc(dev, NR_MSI_VEC, GFP_KERNEL);
@@ -283,34 +277,56 @@ static void xgene_msi_isr(struct irq_desc *desc)
 	chained_irq_exit(chip, desc);
 }
 
-static enum cpuhp_state pci_xgene_online;
-
 static void xgene_msi_remove(struct platform_device *pdev)
 {
-	struct xgene_msi *msi = platform_get_drvdata(pdev);
-
-	if (pci_xgene_online)
-		cpuhp_remove_state(pci_xgene_online);
-	cpuhp_remove_state(CPUHP_PCI_XGENE_DEAD);
+	for (int i = 0; i < NR_HW_IRQS; i++) {
+		unsigned int irq = xgene_msi_ctrl->gic_irq[i];
+		if (!irq)
+			continue;
+		irq_set_chained_handler_and_data(irq, NULL, NULL);
+	}
 
-	xgene_free_domains(msi);
+	if (xgene_msi_ctrl->inner_domain)
+		irq_domain_remove(xgene_msi_ctrl->inner_domain);
 }
 
-static int xgene_msi_hwirq_alloc(unsigned int cpu)
+static int xgene_msi_handler_setup(struct platform_device *pdev)
 {
+	struct xgene_msi *xgene_msi = xgene_msi_ctrl;
 	int i;
-	int err;
 
-	for (i = cpu; i < NR_HW_IRQS; i += num_possible_cpus()) {
-		unsigned int irq = xgene_msi_ctrl->gic_irq[i];
+	for (i = 0; i < NR_HW_IRQS; i++) {
+		u32 msi_val;
+		int irq, err;
+
+		/*
+		 * MSInIRx registers are read-to-clear; before registering
+		 * interrupt handlers, read all of them to clear spurious
+		 * interrupts that may occur before the driver is probed.
+		 */
+		for (int msi_idx = 0; msi_idx < IDX_PER_GROUP; msi_idx++)
+			xgene_msi_ir_read(xgene_msi, i, msi_idx);
+
+		/* Read MSIINTn to confirm */
+		msi_val = xgene_msi_int_read(xgene_msi, i);
+		if (msi_val) {
+			dev_err(&pdev->dev, "Failed to clear spurious IRQ\n");
+			return EINVAL;
+		}
+
+		irq = platform_get_irq(pdev, i);
+		if (irq < 0)
+			return irq;
+
+		xgene_msi->gic_irq[i] = irq;
 
 		/*
 		 * Statically allocate MSI GIC IRQs to each CPU core.
 		 * With 8-core X-Gene v1, 2 MSI GIC IRQs are allocated
 		 * to each core.
 		 */
 		irq_set_status_flags(irq, IRQ_NO_BALANCING);
-		err = irq_set_affinity(irq, cpumask_of(cpu));
+		err = irq_set_affinity(irq, cpumask_of(i % num_possible_cpus()));
 		if (err) {
 			pr_err("failed to set affinity for GIC IRQ");
 			return err;
@@ -323,17 +339,6 @@ static int xgene_msi_hwirq_alloc(unsigned int cpu)
 	return 0;
 }
 
-static int xgene_msi_hwirq_free(unsigned int cpu)
-{
-	struct xgene_msi *msi = xgene_msi_ctrl;
-	int i;
-
-	for (i = cpu; i < NR_HW_IRQS; i += num_possible_cpus())
-		irq_set_chained_handler_and_data(msi->gic_irq[i], NULL, NULL);
-
-	return 0;
-}
-
 static const struct of_device_id xgene_msi_match_table[] = {
 	{.compatible = "apm,xgene1-msi"},
 	{},
@@ -343,7 +348,6 @@ static int xgene_msi_probe(struct platform_device *pdev)
 {
 	struct resource *res;
 	struct xgene_msi *xgene_msi;
-	u32 msi_val, msi_idx;
 	int rc;
 
 	xgene_msi_ctrl = devm_kzalloc(&pdev->dev, sizeof(*xgene_msi_ctrl),
@@ -353,8 +357,6 @@ static int xgene_msi_probe(struct platform_device *pdev)
 
 	xgene_msi = xgene_msi_ctrl;
 
-	platform_set_drvdata(pdev, xgene_msi);
-
 	xgene_msi->msi_regs = devm_platform_get_and_ioremap_resource(pdev, 0, &res);
 	if (IS_ERR(xgene_msi->msi_regs)) {
 		rc = PTR_ERR(xgene_msi->msi_regs);
@@ -374,48 +376,13 @@ static int xgene_msi_probe(struct platform_device *pdev)
 		goto error;
 	}
 
-	for (int irq_index = 0; irq_index < NR_HW_IRQS; irq_index++) {
-		rc = platform_get_irq(pdev, irq_index);
-		if (rc < 0)
-			goto error;
-
-		xgene_msi->gic_irq[irq_index] = rc;
-	}
-
-	/*
-	 * MSInIRx registers are read-to-clear; before registering
-	 * interrupt handlers, read all of them to clear spurious
-	 * interrupts that may occur before the driver is probed.
-	 */
-	for (int irq_index = 0; irq_index < NR_HW_IRQS; irq_index++) {
-		for (msi_idx = 0; msi_idx < IDX_PER_GROUP; msi_idx++)
-			xgene_msi_ir_read(xgene_msi, irq_index, msi_idx);
-
-		/* Read MSIINTn to confirm */
-		msi_val = xgene_msi_int_read(xgene_msi, irq_index);
-		if (msi_val) {
-			dev_err(&pdev->dev, "Failed to clear spurious IRQ\n");
-			rc = -EINVAL;
-			goto error;
-		}
-	}
-
-	rc = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "pci/xgene:online",
-			       xgene_msi_hwirq_alloc, NULL);
-	if (rc < 0)
-		goto err_cpuhp;
-	pci_xgene_online = rc;
-	rc = cpuhp_setup_state(CPUHP_PCI_XGENE_DEAD, "pci/xgene:dead", NULL,
-			       xgene_msi_hwirq_free);
+	rc = xgene_msi_handler_setup(pdev);
 	if (rc)
-		goto err_cpuhp;
+		goto error;
 
 	dev_info(&pdev->dev, "APM X-Gene PCIe MSI driver loaded\n");
 
 	return 0;
-
-err_cpuhp:
-	dev_err(&pdev->dev, "failed to add CPU MSI notifier\n");
 error:
 	xgene_msi_remove(pdev);
 	return rc;