arch/x86/pci/legacy.c

   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);