drivers/pci/rom.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * PCI ROM access routines
   4  *
   5  * (C) Copyright 2004 Jon Smirl <jonsmirl@yahoo.com>
   6  * (C) Copyright 2004 Silicon Graphics, Inc. Jesse Barnes <jbarnes@sgi.com>
   7  */
   8 #include <linux/kernel.h>
   9 #include <linux/export.h>
  10 #include <linux/pci.h>
  11 #include <linux/slab.h>
  12
  13 #include "pci.h"
  14
  15 /**
  16  * pci_enable_rom - enable ROM decoding for a PCI device
  17  * @pdev: PCI device to enable
  18  *
  19  * Enable ROM decoding on @dev.  This involves simply turning on the last
  20  * bit of the PCI ROM BAR.  Note that some cards may share address decoders
  21  * between the ROM and other resources, so enabling it may disable access
  22  * to MMIO registers or other card memory.
  23  */
  24 int pci_enable_rom(struct pci_dev *pdev)
  25 {
  26         struct resource *res = &pdev->resource[PCI_ROM_RESOURCE];
  27         struct pci_bus_region region;
  28         u32 rom_addr;
  29
  30         if (!res->flags)
  31                 return -1;
  32
  33         /* Nothing to enable if we're using a shadow copy in RAM */
  34         if (res->flags & IORESOURCE_ROM_SHADOW)
  35                 return 0;
  36
  37         /*
  38          * Ideally pci_update_resource() would update the ROM BAR address,
  39          * and we would only set the enable bit here.  But apparently some
  40          * devices have buggy ROM BARs that read as zero when disabled.
  41          */
  42         pcibios_resource_to_bus(pdev->bus, &region, res);
  43         pci_read_config_dword(pdev, pdev->rom_base_reg, &rom_addr);
  44         rom_addr &= ~PCI_ROM_ADDRESS_MASK;
  45         rom_addr |= region.start | PCI_ROM_ADDRESS_ENABLE;
  46         pci_write_config_dword(pdev, pdev->rom_base_reg, rom_addr);
  47         return 0;
  48 }
  49 EXPORT_SYMBOL_GPL(pci_enable_rom);
  50
  51 /**
  52  * pci_disable_rom - disable ROM decoding for a PCI device
  53  * @pdev: PCI device to disable
  54  *
  55  * Disable ROM decoding on a PCI device by turning off the last bit in the
  56  * ROM BAR.
  57  */
  58 void pci_disable_rom(struct pci_dev *pdev)
  59 {
  60         struct resource *res = &pdev->resource[PCI_ROM_RESOURCE];
  61         u32 rom_addr;
  62
  63         if (res->flags & IORESOURCE_ROM_SHADOW)
  64                 return;
  65
  66         pci_read_config_dword(pdev, pdev->rom_base_reg, &rom_addr);
  67         rom_addr &= ~PCI_ROM_ADDRESS_ENABLE;
  68         pci_write_config_dword(pdev, pdev->rom_base_reg, rom_addr);
  69 }
  70 EXPORT_SYMBOL_GPL(pci_disable_rom);
  71
  72 /**
  73  * pci_get_rom_size - obtain the actual size of the ROM image
  74  * @pdev: target PCI device
  75  * @rom: kernel virtual pointer to image of ROM
  76  * @size: size of PCI window
  77  *  return: size of actual ROM image
  78  *
  79  * Determine the actual length of the ROM image.
  80  * The PCI window size could be much larger than the
  81  * actual image size.
  82  */
  83 static size_t pci_get_rom_size(struct pci_dev *pdev, void __iomem *rom,
  84                                size_t size)
  85 {
  86         void __iomem *image;
  87         int last_image;
  88         unsigned length;
  89
  90         image = rom;
  91         do {
  92                 void __iomem *pds;
  93                 /* Standard PCI ROMs start out with these bytes 55 AA */
  94                 if (readw(image) != 0xAA55) {
  95                         pci_info(pdev, "Invalid PCI ROM header signature: expecting 0xaa55, got %#06x\n",
  96                                  readw(image));
  97                         break;
  98                 }
  99                 /* get the PCI data structure and check its "PCIR" signature */
 100                 pds = image + readw(image + 24);
 101                 if (readl(pds) != 0x52494350) {
 102                         pci_info(pdev, "Invalid PCI ROM data signature: expecting 0x52494350, got %#010x\n",
 103                                  readl(pds));
 104                         break;
 105                 }
 106                 last_image = readb(pds + 21) & 0x80;
 107                 length = readw(pds + 16);
 108                 image += length * 512;
 109                 /* Avoid iterating through memory outside the resource window */
 110                 if (image >= rom + size)
 111                         break;
 112                 if (!last_image) {
 113                         if (readw(image) != 0xAA55) {
 114                                 pci_info(pdev, "No more image in the PCI ROM\n");
 115                                 break;
 116                         }
 117                 }
 118         } while (length && !last_image);
 119
 120         /* never return a size larger than the PCI resource window */
 121         /* there are known ROMs that get the size wrong */
 122         return min((size_t)(image - rom), size);
 123 }
 124
 125 /**
 126  * pci_map_rom - map a PCI ROM to kernel space
 127  * @pdev: pointer to pci device struct
 128  * @size: pointer to receive size of pci window over ROM
 129  *
 130  * Return: kernel virtual pointer to image of ROM
 131  *
 132  * Map a PCI ROM into kernel space. If ROM is boot video ROM,
 133  * the shadow BIOS copy will be returned instead of the
 134  * actual ROM.
 135  */
 136 void __iomem *pci_map_rom(struct pci_dev *pdev, size_t *size)
 137 {
 138         struct resource *res = &pdev->resource[PCI_ROM_RESOURCE];
 139         loff_t start;
 140         void __iomem *rom;
 141
 142         /* assign the ROM an address if it doesn't have one */
 143         if (res->parent == NULL && pci_assign_resource(pdev, PCI_ROM_RESOURCE))
 144                 return NULL;
 145
 146         start = pci_resource_start(pdev, PCI_ROM_RESOURCE);
 147         *size = pci_resource_len(pdev, PCI_ROM_RESOURCE);
 148         if (*size == 0)
 149                 return NULL;
 150
 151         /* Enable ROM space decodes */
 152         if (pci_enable_rom(pdev))
 153                 return NULL;
 154
 155         rom = ioremap(start, *size);
 156         if (!rom)
 157                 goto err_ioremap;
 158
 159         /*
 160          * Try to find the true size of the ROM since sometimes the PCI window
 161          * size is much larger than the actual size of the ROM.
 162          * True size is important if the ROM is going to be copied.
 163          */
 164         *size = pci_get_rom_size(pdev, rom, *size);
 165         if (!*size)
 166                 goto invalid_rom;
 167
 168         return rom;
 169
 170 invalid_rom:
 171         iounmap(rom);
 172 err_ioremap:
 173         /* restore enable if ioremap fails */
 174         if (!(res->flags & IORESOURCE_ROM_ENABLE))
 175                 pci_disable_rom(pdev);
 176         return NULL;
 177 }
 178 EXPORT_SYMBOL(pci_map_rom);
 179
 180 /**
 181  * pci_unmap_rom - unmap the ROM from kernel space
 182  * @pdev: pointer to pci device struct
 183  * @rom: virtual address of the previous mapping
 184  *
 185  * Remove a mapping of a previously mapped ROM
 186  */
 187 void pci_unmap_rom(struct pci_dev *pdev, void __iomem *rom)
 188 {
 189         struct resource *res = &pdev->resource[PCI_ROM_RESOURCE];
 190
 191         iounmap(rom);
 192
 193         /* Disable again before continuing */
 194         if (!(res->flags & IORESOURCE_ROM_ENABLE))
 195                 pci_disable_rom(pdev);
 196 }
 197 EXPORT_SYMBOL(pci_unmap_rom);
 198
 199 /**
 200  * pci_platform_rom - provides a pointer to any ROM image provided by the
 201  * platform
 202  * @pdev: pointer to pci device struct
 203  * @size: pointer to receive size of pci window over ROM
 204  */
 205 void __iomem *pci_platform_rom(struct pci_dev *pdev, size_t *size)
 206 {
 207         if (pdev->rom && pdev->romlen) {
 208                 *size = pdev->romlen;
 209                 return phys_to_virt((phys_addr_t)pdev->rom);
 210         }
 211
 212         return NULL;
 213 }
 214 EXPORT_SYMBOL(pci_platform_rom);