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