1 // SPDX-License-Identifier: GPL-2.0-only
3 * legacy.c - traditional, old school PCI bus probing
5 #include <linux/init.h>
6 #include <linux/export.h>
8 #include <asm/jailhouse_para.h>
9 #include <asm/pci_x86.h>
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.
15 static void pcibios_fixup_peer_bridges(void)
19 if (pcibios_last_bus <= 0 || pcibios_last_bus > 0xff)
21 DBG("PCI: Peer bridge fixup\n");
23 for (n=0; n <= pcibios_last_bus; n++)
24 pcibios_scan_specific_bus(n);
27 int __init pci_legacy_init(void)
32 pr_info("PCI: Probing PCI hardware\n");
37 void pcibios_scan_specific_bus(int busn)
39 int stride = jailhouse_paravirt() ? 1 : 8;
43 if (pci_find_bus(0, busn))
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);
56 EXPORT_SYMBOL_GPL(pcibios_scan_specific_bus);
58 static int __init pci_subsys_init(void)
61 * The init function returns an non zero value when
62 * pci_legacy_init should be invoked.
64 if (x86_init.pci.init()) {
65 if (pci_legacy_init()) {
66 pr_info("PCI: System does not support PCI\n");
71 pcibios_fixup_peer_bridges();
72 x86_init.pci.init_irq();
77 subsys_initcall(pci_subsys_init);