WSL2-Linux-Kernel/arch/x86/pci/mmconfig_32.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2004 Matthew Wilcox <matthew@wil.cx>
 * Copyright (C) 2004 Intel Corp.
 */

/*
 * mmconfig.c - Low-level direct PCI config space access via MMCONFIG
 */

#include <linux/pci.h>
#include <linux/init.h>
#include <linux/rcupdate.h>
#include <asm/e820/api.h>
#include <asm/pci_x86.h>

/* Assume systems with more busses have correct MCFG */
#define mmcfg_virt_addr ((void __iomem *) fix_to_virt(FIX_PCIE_MCFG))

/* The base address of the last MMCONFIG device accessed */
static u32 mmcfg_last_accessed_device;
static int mmcfg_last_accessed_cpu;

/*
 * Functions for accessing PCI configuration space with MMCONFIG accesses
 */
static u32 get_base_addr(unsigned int seg, int bus, unsigned devfn)
{
	struct pci_mmcfg_region *cfg = pci_mmconfig_lookup(seg, bus);

	if (cfg)
		return cfg->address;
	return 0;
}

/*
 * This is always called under pci_config_lock
 */
static void pci_exp_set_dev_base(unsigned int base, int bus, int devfn)
{
	u32 dev_base = base | PCI_MMCFG_BUS_OFFSET(bus) | (devfn << 12);
	int cpu = smp_processor_id();
	if (dev_base != mmcfg_last_accessed_device ||
	    cpu != mmcfg_last_accessed_cpu) {
		mmcfg_last_accessed_device = dev_base;
		mmcfg_last_accessed_cpu = cpu;
		set_fixmap_nocache(FIX_PCIE_MCFG, dev_base);
	}
}

static int pci_mmcfg_read(unsigned int seg, unsigned int bus,
			  unsigned int devfn, int reg, int len, u32 *value)
{
	unsigned long flags;
	u32 base;

	if ((bus > 255) || (devfn > 255) || (reg > 4095)) {
err:		*value = -1;
		return -EINVAL;
	}

	rcu_read_lock();
	base = get_base_addr(seg, bus, devfn);
	if (!base) {
		rcu_read_unlock();
		goto err;
	}

	raw_spin_lock_irqsave(&pci_config_lock, flags);

	pci_exp_set_dev_base(base, bus, devfn);

	switch (len) {
	case 1:
		*value = mmio_config_readb(mmcfg_virt_addr + reg);
		break;
	case 2:
		*value = mmio_config_readw(mmcfg_virt_addr + reg);
		break;
	case 4:
		*value = mmio_config_readl(mmcfg_virt_addr + reg);
		break;
	}
	raw_spin_unlock_irqrestore(&pci_config_lock, flags);
	rcu_read_unlock();

	return 0;
}

static int pci_mmcfg_write(unsigned int seg, unsigned int bus,
			   unsigned int devfn, int reg, int len, u32 value)
{
	unsigned long flags;
	u32 base;

	if ((bus > 255) || (devfn > 255) || (reg > 4095))
		return -EINVAL;

	rcu_read_lock();
	base = get_base_addr(seg, bus, devfn);
	if (!base) {
		rcu_read_unlock();
		return -EINVAL;
	}

	raw_spin_lock_irqsave(&pci_config_lock, flags);

	pci_exp_set_dev_base(base, bus, devfn);

	switch (len) {
	case 1:
		mmio_config_writeb(mmcfg_virt_addr + reg, value);
		break;
	case 2:
		mmio_config_writew(mmcfg_virt_addr + reg, value);
		break;
	case 4:
		mmio_config_writel(mmcfg_virt_addr + reg, value);
		break;
	}
	raw_spin_unlock_irqrestore(&pci_config_lock, flags);
	rcu_read_unlock();

	return 0;
}

const struct pci_raw_ops pci_mmcfg = {
	.read =		pci_mmcfg_read,
	.write =	pci_mmcfg_write,
};

int __init pci_mmcfg_arch_init(void)
{
	printk(KERN_INFO "PCI: Using MMCONFIG for extended config space\n");
	raw_pci_ext_ops = &pci_mmcfg;
	return 1;
}

void __init pci_mmcfg_arch_free(void)
{
}

int pci_mmcfg_arch_map(struct pci_mmcfg_region *cfg)
{
	return 0;
}

void pci_mmcfg_arch_unmap(struct pci_mmcfg_region *cfg)
{
	unsigned long flags;

	/* Invalidate the cached mmcfg map entry. */
	raw_spin_lock_irqsave(&pci_config_lock, flags);
	mmcfg_last_accessed_device = 0;
	raw_spin_unlock_irqrestore(&pci_config_lock, flags);
}