drivers/pci/rom.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * drivers/pci/rom.c
   4  *
   5  * (C) Copyright 2004 Jon Smirl <jonsmirl@yahoo.com>
   6  * (C) Copyright 2004 Silicon Graphics, Inc. Jesse Barnes <jbarnes@sgi.com>
   7  *
   8  * PCI ROM access routines
   9  */
  10 #include <linux/kernel.h>
  11 #include <linux/export.h>
  12 #include <linux/pci.h>
  13 #include <linux/slab.h>
  14
  15 #include "pci.h"
  16
  17 /**
  18  * pci_enable_rom - enable ROM decoding for a PCI device
  19  * @pdev: PCI device to enable
  20  *
  21  * Enable ROM decoding on @dev.  This involves simply turning on the last
  22  * bit of the PCI ROM BAR.  Note that some cards may share address decoders
  23  * between the ROM and other resources, so enabling it may disable access
  24  * to MMIO registers or other card memory.
  25  */
  26 int pci_enable_rom(struct pci_dev *pdev)
  27 {
  28         struct resource *res = &pdev->resource[PCI_ROM_RESOURCE];
  29         struct pci_bus_region region;
  30         u32 rom_addr;
  31
  32         if (!res->flags)
  33                 return -1;
  34
  35         /* Nothing to enable if we're using a shadow copy in RAM */
  36         if (res->flags & IORESOURCE_ROM_SHADOW)
  37                 return 0;
  38
  39         /*
  40          * Ideally pci_update_resource() would update the ROM BAR address,
  41          * and we would only set the enable bit here.  But apparently some
  42          * devices have buggy ROM BARs that read as zero when disabled.
  43          */
  44         pcibios_resource_to_bus(pdev->bus, &region, res);
  45         pci_read_config_dword(pdev, pdev->rom_base_reg, &rom_addr);
  46         rom_addr &= ~PCI_ROM_ADDRESS_MASK;
  47         rom_addr |= region.start | PCI_ROM_ADDRESS_ENABLE;
  48         pci_write_config_dword(pdev, pdev->rom_base_reg, rom_addr);
  49         return 0;
  50 }
  51 EXPORT_SYMBOL_GPL(pci_enable_rom);
  52
  53 /**
  54  * pci_disable_rom - disable ROM decoding for a PCI device
  55  * @pdev: PCI device to disable
  56  *
  57  * Disable ROM decoding on a PCI device by turning off the last bit in the
  58  * ROM BAR.
  59  */
  60 void pci_disable_rom(struct pci_dev *pdev)
  61 {
  62         struct resource *res = &pdev->resource[PCI_ROM_RESOURCE];
  63         u32 rom_addr;
  64
  65         if (res->flags & IORESOURCE_ROM_SHADOW)
  66                 return;
  67
  68         pci_read_config_dword(pdev, pdev->rom_base_reg, &rom_addr);
  69         rom_addr &= ~PCI_ROM_ADDRESS_ENABLE;
  70         pci_write_config_dword(pdev, pdev->rom_base_reg, rom_addr);
  71 }
  72 EXPORT_SYMBOL_GPL(pci_disable_rom);
  73
  74 /**
  75  * pci_get_rom_size - obtain the actual size of the ROM image
  76  * @pdev: target PCI device
  77  * @rom: kernel virtual pointer to image of ROM
  78  * @size: size of PCI window
  79  *  return: size of actual ROM image
  80  *
  81  * Determine the actual length of the ROM image.
  82  * The PCI window size could be much larger than the
  83  * actual image size.
  84  */
  85 size_t pci_get_rom_size(struct pci_dev *pdev, void __iomem *rom, size_t size)
  86 {
  87         void __iomem *image;
  88         int last_image;
  89         unsigned length;
  90
  91         image = rom;
  92         do {
  93                 void __iomem *pds;
  94                 /* Standard PCI ROMs start out with these bytes 55 AA */
  95                 if (readw(image) != 0xAA55) {
  96                         pci_info(pdev, "Invalid PCI ROM header signature: expecting 0xaa55, got %#06x\n",
  97                                  readw(image));
  98                         break;
  99                 }
 100                 /* get the PCI data structure and check its "PCIR" signature */
 101                 pds = image + readw(image + 24);
 102                 if (readl(pds) != 0x52494350) {
 103                         pci_info(pdev, "Invalid PCI ROM data signature: expecting 0x52494350, got %#010x\n",
 104                                  readl(pds));
 105                         break;
 106                 }
 107                 last_image = readb(pds + 21) & 0x80;
 108                 length = readw(pds + 16);
 109                 image += length * 512;
 110                 /* Avoid iterating through memory outside the resource window */
 111                 if (image > rom + size)
 112                         break;
 113         } while (length && !last_image);
 114
 115         /* never return a size larger than the PCI resource window */
 116         /* there are known ROMs that get the size wrong */
 117         return min((size_t)(image - rom), size);
 118 }
 119
 120 /**
 121  * pci_map_rom - map a PCI ROM to kernel space
 122  * @pdev: pointer to pci device struct
 123  * @size: pointer to receive size of pci window over ROM
 124  *
 125  * Return: kernel virtual pointer to image of ROM
 126  *
 127  * Map a PCI ROM into kernel space. If ROM is boot video ROM,
 128  * the shadow BIOS copy will be returned instead of the
 129  * actual ROM.
 130  */
 131 void __iomem *pci_map_rom(struct pci_dev *pdev, size_t *size)
 132 {
 133         struct resource *res = &pdev->resource[PCI_ROM_RESOURCE];
 134         loff_t start;
 135         void __iomem *rom;
 136
 137         /* assign the ROM an address if it doesn't have one */
 138         if (res->parent == NULL && pci_assign_resource(pdev, PCI_ROM_RESOURCE))
 139                 return NULL;
 140
 141         start = pci_resource_start(pdev, PCI_ROM_RESOURCE);
 142         *size = pci_resource_len(pdev, PCI_ROM_RESOURCE);
 143         if (*size == 0)
 144                 return NULL;
 145
 146         /* Enable ROM space decodes */
 147         if (pci_enable_rom(pdev))
 148                 return NULL;
 149
 150         rom = ioremap(start, *size);
 151         if (!rom)
 152                 goto err_ioremap;
 153
 154         /*
 155          * Try to find the true size of the ROM since sometimes the PCI window
 156          * size is much larger than the actual size of the ROM.
 157          * True size is important if the ROM is going to be copied.
 158          */
 159         *size = pci_get_rom_size(pdev, rom, *size);
 160         if (!*size)
 161                 goto invalid_rom;
 162
 163         return rom;
 164
 165 invalid_rom:
 166         iounmap(rom);
 167 err_ioremap:
 168         /* restore enable if ioremap fails */
 169         if (!(res->flags & IORESOURCE_ROM_ENABLE))
 170                 pci_disable_rom(pdev);
 171         return NULL;
 172 }
 173 EXPORT_SYMBOL(pci_map_rom);
 174
 175 /**
 176  * pci_unmap_rom - unmap the ROM from kernel space
 177  * @pdev: pointer to pci device struct
 178  * @rom: virtual address of the previous mapping
 179  *
 180  * Remove a mapping of a previously mapped ROM
 181  */
 182 void pci_unmap_rom(struct pci_dev *pdev, void __iomem *rom)
 183 {
 184         struct resource *res = &pdev->resource[PCI_ROM_RESOURCE];
 185
 186         iounmap(rom);
 187
 188         /* Disable again before continuing */
 189         if (!(res->flags & IORESOURCE_ROM_ENABLE))
 190                 pci_disable_rom(pdev);
 191 }
 192 EXPORT_SYMBOL(pci_unmap_rom);
 193
 194 /**
 195  * pci_platform_rom - provides a pointer to any ROM image provided by the
 196  * platform
 197  * @pdev: pointer to pci device struct
 198  * @size: pointer to receive size of pci window over ROM
 199  */
 200 void __iomem *pci_platform_rom(struct pci_dev *pdev, size_t *size)
 201 {
 202         if (pdev->rom && pdev->romlen) {
 203                 *size = pdev->romlen;
 204                 return phys_to_virt((phys_addr_t)pdev->rom);
 205         }
 206
 207         return NULL;
 208 }
 209 EXPORT_SYMBOL(pci_platform_rom);