// 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 ECAM 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);
}