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  */
pcibios_fixup_peer_bridges(void)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 
pci_legacy_init(void)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 
pcibios_scan_specific_bus(int busn)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 
pci_subsys_init(void)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