linux_kernel/arch/x86/pci/early.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/kernel.h>
#include <linux/pci.h>
#include <asm/pci-direct.h>
#include <asm/io.h>
#include <asm/pci_x86.h>

/* Direct PCI access. This is used for PCI accesses in early boot before
   the PCI subsystem works. */

u32 read_pci_config(u8 bus, u8 slot, u8 func, u8 offset)
{
	u32 v;
	outl(0x80000000 | (bus<<16) | (slot<<11) | (func<<8) | offset, 0xcf8);
	v = inl(0xcfc);
	return v;
}

u8 read_pci_config_byte(u8 bus, u8 slot, u8 func, u8 offset)
{
	u8 v;
	outl(0x80000000 | (bus<<16) | (slot<<11) | (func<<8) | offset, 0xcf8);
	v = inb(0xcfc + (offset&3));
	return v;
}

u16 read_pci_config_16(u8 bus, u8 slot, u8 func, u8 offset)
{
	u16 v;
	outl(0x80000000 | (bus<<16) | (slot<<11) | (func<<8) | offset, 0xcf8);
	v = inw(0xcfc + (offset&2));
	return v;
}

void write_pci_config(u8 bus, u8 slot, u8 func, u8 offset,
				    u32 val)
{
	outl(0x80000000 | (bus<<16) | (slot<<11) | (func<<8) | offset, 0xcf8);
	outl(val, 0xcfc);
}

void write_pci_config_byte(u8 bus, u8 slot, u8 func, u8 offset, u8 val)
{
	outl(0x80000000 | (bus<<16) | (slot<<11) | (func<<8) | offset, 0xcf8);
	outb(val, 0xcfc + (offset&3));
}

void write_pci_config_16(u8 bus, u8 slot, u8 func, u8 offset, u16 val)
{
	outl(0x80000000 | (bus<<16) | (slot<<11) | (func<<8) | offset, 0xcf8);
	outw(val, 0xcfc + (offset&2));
}

int early_pci_allowed(void)
{
	return (pci_probe & (PCI_PROBE_CONF1|PCI_PROBE_NOEARLY)) ==
			PCI_PROBE_CONF1;
}

void early_dump_pci_device(u8 bus, u8 slot, u8 func)
{
	int i;
	int j;
	u32 val;

	printk(KERN_INFO "pci 0000:%02x:%02x.%d config space:",
	       bus, slot, func);

	for (i = 0; i < 256; i += 4) {
		if (!(i & 0x0f))
			printk("\n  %02x:",i);

		val = read_pci_config(bus, slot, func, i);
		for (j = 0; j < 4; j++) {
			printk(" %02x", val & 0xff);
			val >>= 8;
		}
	}
	printk("\n");
}

void early_dump_pci_devices(void)
{
	unsigned bus, slot, func;

	if (!early_pci_allowed())
		return;

	for (bus = 0; bus < 256; bus++) {
		for (slot = 0; slot < 32; slot++) {
			for (func = 0; func < 8; func++) {
				u32 class;
				u8 type;

				class = read_pci_config(bus, slot, func,
							PCI_CLASS_REVISION);
				if (class == 0xffffffff)
					continue;

				early_dump_pci_device(bus, slot, func);

				if (func == 0) {
					type = read_pci_config_byte(bus, slot,
								    func,
							       PCI_HEADER_TYPE);
					if (!(type & 0x80))
						break;
				}
			}
		}
	}
}