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Subject[PATCH v2] x86/PCI: Handle PIRQ routing tables with no router device given
PIRQ routing tables provided by the PCI BIOS usually specify the PCI 
vendor:device ID as well as the bus address of the device implementing
the PIRQ router, e.g.:

PCI: Interrupt Routing Table found at 0xc00fde10
[...]
PCI: Attempting to find IRQ router for [8086:7000]
pci 0000:00:07.0: PIIX/ICH IRQ router [8086:7000]

however in some cases they do not, in which case we fail to match the
router handler, e.g.:

PCI: Interrupt Routing Table found at 0xc00fdae0
[...]
PCI: Attempting to find IRQ router for [0000:0000]
PCI: Interrupt router not found at 00:00

This is because we always match the vendor:device ID and the bus address
literally, even if they are all zeros.

Handle this case then and iterate over all PCI devices until we find a
matching router handler if the vendor ID given by the routing table is
the invalid value of zero.

Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
---
Changes from v1:

- preinitialise `dev' in `pirq_find_router' for `for_each_pci_dev',

- avoid calling `pirq_try_router' with null `dev'.
---
arch/x86/pci/irq.c | 64 ++++++++++++++++++++++++++++++++++++-----------------
1 file changed, 44 insertions(+), 20 deletions(-)

linux-x86-pirq-router-nodev.diff
Index: linux-macro-ide-tty/arch/x86/pci/irq.c
===================================================================
--- linux-macro-ide-tty.orig/arch/x86/pci/irq.c
+++ linux-macro-ide-tty/arch/x86/pci/irq.c
@@ -908,10 +908,32 @@ static struct pci_dev *pirq_router_dev;
* chipset" ?
*/

+static bool __init pirq_try_router(struct irq_router *r,
+ struct irq_routing_table *rt,
+ struct pci_dev *dev)
+{
+ struct irq_router_handler *h;
+
+ DBG(KERN_DEBUG "PCI: Trying IRQ router for [%04x:%04x]\n",
+ dev->vendor, dev->device);
+
+ for (h = pirq_routers; h->vendor; h++) {
+ /* First look for a router match */
+ if (rt->rtr_vendor == h->vendor &&
+ h->probe(r, dev, rt->rtr_device))
+ return true;
+ /* Fall back to a device match */
+ if (dev->vendor == h->vendor &&
+ h->probe(r, dev, dev->device))
+ return true;
+ }
+ return false;
+}
+
static void __init pirq_find_router(struct irq_router *r)
{
struct irq_routing_table *rt = pirq_table;
- struct irq_router_handler *h;
+ struct pci_dev *dev;

#ifdef CONFIG_PCI_BIOS
if (!rt->signature) {
@@ -930,27 +952,29 @@ static void __init pirq_find_router(stru
DBG(KERN_DEBUG "PCI: Attempting to find IRQ router for [%04x:%04x]\n",
rt->rtr_vendor, rt->rtr_device);

- pirq_router_dev = pci_get_domain_bus_and_slot(0, rt->rtr_bus,
- rt->rtr_devfn);
- if (!pirq_router_dev) {
- DBG(KERN_DEBUG "PCI: Interrupt router not found at "
- "%02x:%02x\n", rt->rtr_bus, rt->rtr_devfn);
- return;
+ /* Use any vendor:device provided by the routing table or try all. */
+ if (rt->rtr_vendor) {
+ dev = pci_get_domain_bus_and_slot(0, rt->rtr_bus,
+ rt->rtr_devfn);
+ if (dev && pirq_try_router(r, rt, dev))
+ pirq_router_dev = dev;
+ } else {
+ dev = NULL;
+ for_each_pci_dev(dev) {
+ if (pirq_try_router(r, rt, dev)) {
+ pirq_router_dev = dev;
+ break;
+ }
+ }
}

- for (h = pirq_routers; h->vendor; h++) {
- /* First look for a router match */
- if (rt->rtr_vendor == h->vendor &&
- h->probe(r, pirq_router_dev, rt->rtr_device))
- break;
- /* Fall back to a device match */
- if (pirq_router_dev->vendor == h->vendor &&
- h->probe(r, pirq_router_dev, pirq_router_dev->device))
- break;
- }
- dev_info(&pirq_router_dev->dev, "%s IRQ router [%04x:%04x]\n",
- pirq_router.name,
- pirq_router_dev->vendor, pirq_router_dev->device);
+ if (pirq_router_dev)
+ dev_info(&pirq_router_dev->dev, "%s IRQ router [%04x:%04x]\n",
+ pirq_router.name,
+ pirq_router_dev->vendor, pirq_router_dev->device);
+ else
+ DBG(KERN_DEBUG "PCI: Interrupt router not found at "
+ "%02x:%02x\n", rt->rtr_bus, rt->rtr_devfn);

/* The device remains referenced for the kernel lifetime */
}
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