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/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);