1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * legacy.c - traditional, old school PCI bus probing
4 */
5 #include <linux/init.h>
6 #include <linux/export.h>
7 #include <linux/pci.h>
8 #include <asm/jailhouse_para.h>
9 #include <asm/pci_x86.h>
10
11 /*
12 * Discover remaining PCI buses in case there are peer host bridges.
13 * We use the number of last PCI bus provided by the PCI BIOS.
14 */
15 static void pcibios_fixup_peer_bridges(void)
16 {
17 int n;
18
19 if (pcibios_last_bus <= 0 || pcibios_last_bus > 0xff)
20 return;
21 DBG("PCI: Peer bridge fixup\n");
22
23 for (n=0; n <= pcibios_last_bus; n++)
24 pcibios_scan_specific_bus(n);
25 }
26
27 int __init pci_legacy_init(void)
28 {
29 if (!raw_pci_ops)
30 return 1;
31
32 pr_info("PCI: Probing PCI hardware\n");
33 pcibios_scan_root(0);
34 return 0;
35 }
36
37 void pcibios_scan_specific_bus(int busn)
38 {
39 int stride = jailhouse_paravirt() ? 1 : 8;
40 int devfn;
41 u32 l;
42
43 if (pci_find_bus(0, busn))
44 return;
45
46 for (devfn = 0; devfn < 256; devfn += stride) {
47 if (!raw_pci_read(0, busn, devfn, PCI_VENDOR_ID, 2, &l) &&
48 l != 0x0000 && l != 0xffff) {
49 DBG("Found device at %02x:%02x [%04x]\n", busn, devfn, l);
50 pr_info("PCI: Discovered peer bus %02x\n", busn);
51 pcibios_scan_root(busn);
52 return;
53 }
54 }
55 }
56 EXPORT_SYMBOL_GPL(pcibios_scan_specific_bus);
57
58 static int __init pci_subsys_init(void)
59 {
60 /*
61 * The init function returns an non zero value when
62 * pci_legacy_init should be invoked.
63 */
64 if (x86_init.pci.init()) {
65 if (pci_legacy_init()) {
66 pr_info("PCI: System does not support PCI\n");
67 return -ENODEV;
68 }
69 }
70
71 pcibios_fixup_peer_bridges();
72 x86_init.pci.init_irq();
73 pcibios_init();
74
75 return 0;
76 }
77 subsys_initcall(pci_subsys_init);
78
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