| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * Support routines for initializing a PCI subsystem |
| * |
| * Extruded from code written by |
| * Dave Rusling (david.rusling@reo.mts.dec.com) |
| * David Mosberger (davidm@cs.arizona.edu) |
| * David Miller (davem@redhat.com) |
| */ |
| |
| #include <linux/kernel.h> |
| #include <linux/pci.h> |
| #include <linux/errno.h> |
| #include <linux/ioport.h> |
| #include <linux/cache.h> |
| #include "pci.h" |
| |
| void pci_assign_irq(struct pci_dev *dev) |
| { |
| u8 pin; |
| u8 slot = -1; |
| int irq = 0; |
| struct pci_host_bridge *hbrg = pci_find_host_bridge(dev->bus); |
| |
| if (!(hbrg->map_irq)) { |
| pci_dbg(dev, "runtime IRQ mapping not provided by arch\n"); |
| return; |
| } |
| |
| /* |
| * If this device is not on the primary bus, we need to figure out |
| * which interrupt pin it will come in on. We know which slot it |
| * will come in on because that slot is where the bridge is. Each |
| * time the interrupt line passes through a PCI-PCI bridge we must |
| * apply the swizzle function. |
| */ |
| pci_read_config_byte(dev, PCI_INTERRUPT_PIN, &pin); |
| /* Cope with illegal. */ |
| if (pin > 4) |
| pin = 1; |
| |
| if (pin) { |
| /* Follow the chain of bridges, swizzling as we go. */ |
| if (hbrg->swizzle_irq) |
| slot = (*(hbrg->swizzle_irq))(dev, &pin); |
| |
| /* |
| * If a swizzling function is not used, map_irq() must |
| * ignore slot. |
| */ |
| irq = (*(hbrg->map_irq))(dev, slot, pin); |
| if (irq == -1) |
| irq = 0; |
| } |
| dev->irq = irq; |
| |
| pci_dbg(dev, "assign IRQ: got %d\n", dev->irq); |
| |
| /* |
| * Always tell the device, so the driver knows what is the real IRQ |
| * to use; the device does not use it. |
| */ |
| pci_write_config_byte(dev, PCI_INTERRUPT_LINE, irq); |
| } |
