arch/x86/pci/legacy.c

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