PCI: add routines for debugging and handling lost interrupts

We're getting a lot of storage drivers blamed for interrupt misrouting
issues.  This patch provides a standard way of reporting the problem
... and, if possible, correcting it.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/Makefile

@@ -3,7 +3,8 @@
 #
 
 obj-y		+= access.o bus.o probe.o remove.o pci.o quirks.o slot.o \
-			pci-driver.o search.o pci-sysfs.o rom.o setup-res.o
+			pci-driver.o search.o pci-sysfs.o rom.o setup-res.o \
+			irq.o
 obj-$(CONFIG_PROC_FS) += proc.o
 
 # Build PCI Express stuff if needed

drivers/pci/irq.c

@@ -0,0 +1,60 @@
+/*
+ * PCI IRQ failure handing code
+ *
+ * Copyright (c) 2008 James Bottomley <James.Bottomley@HansenPartnership.com>
+ */
+
+#include <linux/acpi.h>
+#include <linux/device.h>
+#include <linux/kernel.h>
+#include <linux/pci.h>
+
+static void pci_note_irq_problem(struct pci_dev *pdev, const char *reason)
+{
+	struct pci_dev *parent = to_pci_dev(pdev->dev.parent);
+
+	dev_printk(KERN_ERR, &pdev->dev,
+		   "Potentially misrouted IRQ (Bridge %s %04x:%04x)\n",
+		   parent->dev.bus_id, parent->vendor, parent->device);
+	dev_printk(KERN_ERR, &pdev->dev, "%s\n", reason);
+	dev_printk(KERN_ERR, &pdev->dev, "Please report to linux-kernel@vger.kernel.org\n");
+	WARN_ON(1);
+}
+
+/**
+ * pci_lost_interrupt - reports a lost PCI interrupt
+ * @pdev:	device whose interrupt is lost
+ * 
+ * The primary function of this routine is to report a lost interrupt
+ * in a standard way which users can recognise (instead of blaming the
+ * driver).
+ *
+ * Returns:
+ *  a suggestion for fixing it (although the driver is not required to
+ * act on this).
+ */
+enum pci_lost_interrupt_reason pci_lost_interrupt(struct pci_dev *pdev)
+{
+	if (pdev->msi_enabled || pdev->msix_enabled) {
+		enum pci_lost_interrupt_reason ret;
+
+		if (pdev->msix_enabled) {
+			pci_note_irq_problem(pdev, "MSIX routing failure");
+			ret = PCI_LOST_IRQ_DISABLE_MSIX;
+		} else {
+			pci_note_irq_problem(pdev, "MSI routing failure");
+			ret = PCI_LOST_IRQ_DISABLE_MSI;
+		}
+		return ret;
+	}
+#ifdef CONFIG_ACPI
+	if (!(acpi_disabled || acpi_noirq)) {
+		pci_note_irq_problem(pdev, "Potential ACPI misrouting please reboot with acpi=noirq");
+		/* currently no way to fix acpi on the fly */
+		return PCI_LOST_IRQ_DISABLE_ACPI;
+	}
+#endif
+	pci_note_irq_problem(pdev, "unknown cause (not MSI or ACPI)");
+	return PCI_LOST_IRQ_NO_INFORMATION;
+}
+EXPORT_SYMBOL(pci_lost_interrupt);

include/linux/pci.h

@@ -546,6 +546,13 @@ struct pci_dev __deprecated *pci_find_slot(unsigned int bus,
 					   unsigned int devfn);
 #endif /* CONFIG_PCI_LEGACY */
 
+enum pci_lost_interrupt_reason {
+	PCI_LOST_IRQ_NO_INFORMATION = 0,
+	PCI_LOST_IRQ_DISABLE_MSI,
+	PCI_LOST_IRQ_DISABLE_MSIX,
+	PCI_LOST_IRQ_DISABLE_ACPI,
+};
+enum pci_lost_interrupt_reason pci_lost_interrupt(struct pci_dev *dev);
 int pci_find_capability(struct pci_dev *dev, int cap);
 int pci_find_next_capability(struct pci_dev *dev, u8 pos, int cap);
 int pci_find_ext_capability(struct pci_dev *dev, int cap);