// SPDX-License-Identifier: GPL-2.0-only
/*
 * legacy.c - traditional, old school PCI bus probing
 */
#include <linux/init.h>
#include <linux/export.h>
#include <linux/pci.h>
#include <asm/jailhouse_para.h>
#include <asm/pci_x86.h>

/*
 * Discover remaining PCI buses in case there are peer host bridges.
 * We use the number of last PCI bus provided by the PCI BIOS.
 */
static void pcibios_fixup_peer_bridges(void)
{
        int n;

        if (pcibios_last_bus <= 0 || pcibios_last_bus > 0xff)
                return;
        DBG("PCI: Peer bridge fixup\n");

        for (n=0; n <= pcibios_last_bus; n++)
                pcibios_scan_specific_bus(n);
}

int __init pci_legacy_init(void)
{
        if (!raw_pci_ops)
                return 1;

        pr_info("PCI: Probing PCI hardware\n");
        pcibios_scan_root(0);
        return 0;
}

void pcibios_scan_specific_bus(int busn)
{
        int stride = jailhouse_paravirt() ? 1 : 8;
        int devfn;
        u32 l;

        if (pci_find_bus(0, busn))
                return;

        for (devfn = 0; devfn < 256; devfn += stride) {
                if (!raw_pci_read(0, busn, devfn, PCI_VENDOR_ID, 2, &l) &&
                    l != 0x0000 && l != 0xffff) {
                        DBG("Found device at %02x:%02x [%04x]\n", busn, devfn, l);
                        pr_info("PCI: Discovered peer bus %02x\n", busn);
                        pcibios_scan_root(busn);
                        return;
                }
        }
}
EXPORT_SYMBOL_GPL(pcibios_scan_specific_bus);

static int __init pci_subsys_init(void)
{
        /*
         * The init function returns an non zero value when
         * pci_legacy_init should be invoked.
         */
        if (x86_init.pci.init()) {
                if (pci_legacy_init()) {
                        pr_info("PCI: System does not support PCI\n");
                        return -ENODEV;
                }
        }

        pcibios_fixup_peer_bridges();
        x86_init.pci.init_irq();
        pcibios_init();

        return 0;
}
subsys_initcall(pci_subsys_init);