1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * Support routines for initializing a PCI subsystem
4*4882a593Smuzhiyun *
5*4882a593Smuzhiyun * Extruded from code written by
6*4882a593Smuzhiyun * Dave Rusling (david.rusling@reo.mts.dec.com)
7*4882a593Smuzhiyun * David Mosberger (davidm@cs.arizona.edu)
8*4882a593Smuzhiyun * David Miller (davem@redhat.com)
9*4882a593Smuzhiyun */
10*4882a593Smuzhiyun
11*4882a593Smuzhiyun
12*4882a593Smuzhiyun #include <linux/kernel.h>
13*4882a593Smuzhiyun #include <linux/pci.h>
14*4882a593Smuzhiyun #include <linux/errno.h>
15*4882a593Smuzhiyun #include <linux/ioport.h>
16*4882a593Smuzhiyun #include <linux/cache.h>
17*4882a593Smuzhiyun #include "pci.h"
18*4882a593Smuzhiyun
pci_assign_irq(struct pci_dev * dev)19*4882a593Smuzhiyun void pci_assign_irq(struct pci_dev *dev)
20*4882a593Smuzhiyun {
21*4882a593Smuzhiyun u8 pin;
22*4882a593Smuzhiyun u8 slot = -1;
23*4882a593Smuzhiyun int irq = 0;
24*4882a593Smuzhiyun struct pci_host_bridge *hbrg = pci_find_host_bridge(dev->bus);
25*4882a593Smuzhiyun
26*4882a593Smuzhiyun if (!(hbrg->map_irq)) {
27*4882a593Smuzhiyun pci_dbg(dev, "runtime IRQ mapping not provided by arch\n");
28*4882a593Smuzhiyun return;
29*4882a593Smuzhiyun }
30*4882a593Smuzhiyun
31*4882a593Smuzhiyun /* If this device is not on the primary bus, we need to figure out
32*4882a593Smuzhiyun which interrupt pin it will come in on. We know which slot it
33*4882a593Smuzhiyun will come in on 'cos that slot is where the bridge is. Each
34*4882a593Smuzhiyun time the interrupt line passes through a PCI-PCI bridge we must
35*4882a593Smuzhiyun apply the swizzle function. */
36*4882a593Smuzhiyun
37*4882a593Smuzhiyun pci_read_config_byte(dev, PCI_INTERRUPT_PIN, &pin);
38*4882a593Smuzhiyun /* Cope with illegal. */
39*4882a593Smuzhiyun if (pin > 4)
40*4882a593Smuzhiyun pin = 1;
41*4882a593Smuzhiyun
42*4882a593Smuzhiyun if (pin) {
43*4882a593Smuzhiyun /* Follow the chain of bridges, swizzling as we go. */
44*4882a593Smuzhiyun if (hbrg->swizzle_irq)
45*4882a593Smuzhiyun slot = (*(hbrg->swizzle_irq))(dev, &pin);
46*4882a593Smuzhiyun
47*4882a593Smuzhiyun /*
48*4882a593Smuzhiyun * If a swizzling function is not used map_irq must
49*4882a593Smuzhiyun * ignore slot
50*4882a593Smuzhiyun */
51*4882a593Smuzhiyun irq = (*(hbrg->map_irq))(dev, slot, pin);
52*4882a593Smuzhiyun if (irq == -1)
53*4882a593Smuzhiyun irq = 0;
54*4882a593Smuzhiyun }
55*4882a593Smuzhiyun dev->irq = irq;
56*4882a593Smuzhiyun
57*4882a593Smuzhiyun pci_dbg(dev, "assign IRQ: got %d\n", dev->irq);
58*4882a593Smuzhiyun
59*4882a593Smuzhiyun /* Always tell the device, so the driver knows what is
60*4882a593Smuzhiyun the real IRQ to use; the device does not use it. */
61*4882a593Smuzhiyun pci_write_config_byte(dev, PCI_INTERRUPT_LINE, irq);
62*4882a593Smuzhiyun }
63