// SPDX-License-Identifier: GPL-2.0
/*
 * PCI ROM access routines
 *
 * (C) Copyright 2004 Jon Smirl <jonsmirl@yahoo.com>
 * (C) Copyright 2004 Silicon Graphics, Inc. Jesse Barnes <jbarnes@sgi.com>
 */
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/pci.h>
#include <linux/slab.h>

#include "pci.h"

/**
 * pci_enable_rom - enable ROM decoding for a PCI device
 * @pdev: PCI device to enable
 *
 * Enable ROM decoding on @dev.  This involves simply turning on the last
 * bit of the PCI ROM BAR.  Note that some cards may share address decoders
 * between the ROM and other resources, so enabling it may disable access
 * to MMIO registers or other card memory.
 */
int pci_enable_rom(struct pci_dev *pdev)
{
        struct resource *res = &pdev->resource[PCI_ROM_RESOURCE];
        struct pci_bus_region region;
        u32 rom_addr;

        if (!res->flags)
                return -1;

        /* Nothing to enable if we're using a shadow copy in RAM */
        if (res->flags & IORESOURCE_ROM_SHADOW)
                return 0;

        /*
         * Ideally pci_update_resource() would update the ROM BAR address,
         * and we would only set the enable bit here.  But apparently some
         * devices have buggy ROM BARs that read as zero when disabled.
         */
        pcibios_resource_to_bus(pdev->bus, &region, res);
        pci_read_config_dword(pdev, pdev->rom_base_reg, &rom_addr);
        rom_addr &= ~PCI_ROM_ADDRESS_MASK;
        rom_addr |= region.start | PCI_ROM_ADDRESS_ENABLE;
        pci_write_config_dword(pdev, pdev->rom_base_reg, rom_addr);
        return 0;
}
EXPORT_SYMBOL_GPL(pci_enable_rom);

/**
 * pci_disable_rom - disable ROM decoding for a PCI device
 * @pdev: PCI device to disable
 *
 * Disable ROM decoding on a PCI device by turning off the last bit in the
 * ROM BAR.
 */
void pci_disable_rom(struct pci_dev *pdev)
{
        struct resource *res = &pdev->resource[PCI_ROM_RESOURCE];
        u32 rom_addr;

        if (res->flags & IORESOURCE_ROM_SHADOW)
                return;

        pci_read_config_dword(pdev, pdev->rom_base_reg, &rom_addr);
        rom_addr &= ~PCI_ROM_ADDRESS_ENABLE;
        pci_write_config_dword(pdev, pdev->rom_base_reg, rom_addr);
}
EXPORT_SYMBOL_GPL(pci_disable_rom);

/**
 * pci_get_rom_size - obtain the actual size of the ROM image
 * @pdev: target PCI device
 * @rom: kernel virtual pointer to image of ROM
 * @size: size of PCI window
 *  return: size of actual ROM image
 *
 * Determine the actual length of the ROM image.
 * The PCI window size could be much larger than the
 * actual image size.
 */
static size_t pci_get_rom_size(struct pci_dev *pdev, void __iomem *rom,
                               size_t size)
{
        void __iomem *image;
        int last_image;
        unsigned int length;

        image = rom;
        do {
                void __iomem *pds;
                /* Standard PCI ROMs start out with these bytes 55 AA */
                if (readw(image) != 0xAA55) {
                        pci_info(pdev, "Invalid PCI ROM header signature: expecting 0xaa55, got %#06x\n",
                                 readw(image));
                        break;
                }
                /* get the PCI data structure and check its "PCIR" signature */
                pds = image + readw(image + 24);
                if (readl(pds) != 0x52494350) {
                        pci_info(pdev, "Invalid PCI ROM data signature: expecting 0x52494350, got %#010x\n",
                                 readl(pds));
                        break;
                }
                last_image = readb(pds + 21) & 0x80;
                length = readw(pds + 16);
                image += length * 512;
                /* Avoid iterating through memory outside the resource window */
                if (image >= rom + size)
                        break;
                if (!last_image) {
                        if (readw(image) != 0xAA55) {
                                pci_info(pdev, "No more image in the PCI ROM\n");
                                break;
                        }
                }
        } while (length && !last_image);

        /* never return a size larger than the PCI resource window */
        /* there are known ROMs that get the size wrong */
        return min((size_t)(image - rom), size);
}

/**
 * pci_map_rom - map a PCI ROM to kernel space
 * @pdev: pointer to pci device struct
 * @size: pointer to receive size of pci window over ROM
 *
 * Return: kernel virtual pointer to image of ROM
 *
 * Map a PCI ROM into kernel space. If ROM is boot video ROM,
 * the shadow BIOS copy will be returned instead of the
 * actual ROM.
 */
void __iomem *pci_map_rom(struct pci_dev *pdev, size_t *size)
{
        struct resource *res = &pdev->resource[PCI_ROM_RESOURCE];
        loff_t start;
        void __iomem *rom;

        /* assign the ROM an address if it doesn't have one */
        if (res->parent == NULL && pci_assign_resource(pdev, PCI_ROM_RESOURCE))
                return NULL;

        start = pci_resource_start(pdev, PCI_ROM_RESOURCE);
        *size = pci_resource_len(pdev, PCI_ROM_RESOURCE);
        if (*size == 0)
                return NULL;

        /* Enable ROM space decodes */
        if (pci_enable_rom(pdev))
                return NULL;

        rom = ioremap(start, *size);
        if (!rom)
                goto err_ioremap;

        /*
         * Try to find the true size of the ROM since sometimes the PCI window
         * size is much larger than the actual size of the ROM.
         * True size is important if the ROM is going to be copied.
         */
        *size = pci_get_rom_size(pdev, rom, *size);
        if (!*size)
                goto invalid_rom;

        return rom;

invalid_rom:
        iounmap(rom);
err_ioremap:
        /* restore enable if ioremap fails */
        if (!(res->flags & IORESOURCE_ROM_ENABLE))
                pci_disable_rom(pdev);
        return NULL;
}
EXPORT_SYMBOL(pci_map_rom);

/**
 * pci_unmap_rom - unmap the ROM from kernel space
 * @pdev: pointer to pci device struct
 * @rom: virtual address of the previous mapping
 *
 * Remove a mapping of a previously mapped ROM
 */
void pci_unmap_rom(struct pci_dev *pdev, void __iomem *rom)
{
        struct resource *res = &pdev->resource[PCI_ROM_RESOURCE];

        iounmap(rom);

        /* Disable again before continuing */
        if (!(res->flags & IORESOURCE_ROM_ENABLE))
                pci_disable_rom(pdev);
}
EXPORT_SYMBOL(pci_unmap_rom);