xref: /openbmc/linux/arch/x86/pci/legacy.c (revision ba61bb17)
1 /*
2  * legacy.c - traditional, old school PCI bus probing
3  */
4 #include <linux/init.h>
5 #include <linux/export.h>
6 #include <linux/pci.h>
7 #include <asm/jailhouse_para.h>
8 #include <asm/pci_x86.h>
9 
10 /*
11  * Discover remaining PCI buses in case there are peer host bridges.
12  * We use the number of last PCI bus provided by the PCI BIOS.
13  */
14 static void pcibios_fixup_peer_bridges(void)
15 {
16 	int n;
17 
18 	if (pcibios_last_bus <= 0 || pcibios_last_bus > 0xff)
19 		return;
20 	DBG("PCI: Peer bridge fixup\n");
21 
22 	for (n=0; n <= pcibios_last_bus; n++)
23 		pcibios_scan_specific_bus(n);
24 }
25 
26 int __init pci_legacy_init(void)
27 {
28 	if (!raw_pci_ops)
29 		return 1;
30 
31 	pr_info("PCI: Probing PCI hardware\n");
32 	pcibios_scan_root(0);
33 	return 0;
34 }
35 
36 void pcibios_scan_specific_bus(int busn)
37 {
38 	int stride = jailhouse_paravirt() ? 1 : 8;
39 	int devfn;
40 	u32 l;
41 
42 	if (pci_find_bus(0, busn))
43 		return;
44 
45 	for (devfn = 0; devfn < 256; devfn += stride) {
46 		if (!raw_pci_read(0, busn, devfn, PCI_VENDOR_ID, 2, &l) &&
47 		    l != 0x0000 && l != 0xffff) {
48 			DBG("Found device at %02x:%02x [%04x]\n", busn, devfn, l);
49 			pr_info("PCI: Discovered peer bus %02x\n", busn);
50 			pcibios_scan_root(busn);
51 			return;
52 		}
53 	}
54 }
55 EXPORT_SYMBOL_GPL(pcibios_scan_specific_bus);
56 
57 static int __init pci_subsys_init(void)
58 {
59 	/*
60 	 * The init function returns an non zero value when
61 	 * pci_legacy_init should be invoked.
62 	 */
63 	if (x86_init.pci.init()) {
64 		if (pci_legacy_init()) {
65 			pr_info("PCI: System does not support PCI\n");
66 			return -ENODEV;
67 		}
68 	}
69 
70 	pcibios_fixup_peer_bridges();
71 	x86_init.pci.init_irq();
72 	pcibios_init();
73 
74 	return 0;
75 }
76 subsys_initcall(pci_subsys_init);
77