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 size_t pci_get_rom_size(struct pci_dev *pdev, void __iomem *rom, size_t size)
  84 {
  85         void __iomem *image;
  86         int last_image;
  87         unsigned length;
  88
  89         image = rom;
  90         do {
  91                 void __iomem *pds;
  92                 /* Standard PCI ROMs start out with these bytes 55 AA */
  93                 if (readw(image) != 0xAA55) {
  94                         pci_info(pdev, "Invalid PCI ROM header signature: expecting 0xaa55, got %#06x\n",
  95                                  readw(image));
  96                         break;
  97                 }
  98                 /* get the PCI data structure and check its "PCIR" signature */
  99                 pds = image + readw(image + 24);
 100                 if (readl(pds) != 0x52494350) {
 101                         pci_info(pdev, "Invalid PCI ROM data signature: expecting 0x52494350, got %#010x\n",
 102                                  readl(pds));
 103                         break;
 104                 }
 105                 last_image = readb(pds + 21) & 0x80;
 106                 length = readw(pds + 16);
 107                 image += length * 512;
 108                 /* Avoid iterating through memory outside the resource window */
 109                 if (image > rom + size)
 110                         break;
 111         } while (length && !last_image);
 112
 113         /* never return a size larger than the PCI resource window */
 114         /* there are known ROMs that get the size wrong */
 115         return min((size_t)(image - rom), size);
 116 }
 117
 118 /**
 119  * pci_map_rom - map a PCI ROM to kernel space
 120  * @pdev: pointer to pci device struct
 121  * @size: pointer to receive size of pci window over ROM
 122  *
 123  * Return: kernel virtual pointer to image of ROM
 124  *
 125  * Map a PCI ROM into kernel space. If ROM is boot video ROM,
 126  * the shadow BIOS copy will be returned instead of the
 127  * actual ROM.
 128  */
 129 void __iomem *pci_map_rom(struct pci_dev *pdev, size_t *size)
 130 {
 131         struct resource *res = &pdev->resource[PCI_ROM_RESOURCE];
 132         loff_t start;
 133         void __iomem *rom;
 134
 135         /* assign the ROM an address if it doesn't have one */
 136         if (res->parent == NULL && pci_assign_resource(pdev, PCI_ROM_RESOURCE))
 137                 return NULL;
 138
 139         start = pci_resource_start(pdev, PCI_ROM_RESOURCE);
 140         *size = pci_resource_len(pdev, PCI_ROM_RESOURCE);
 141         if (*size == 0)
 142                 return NULL;
 143
 144         /* Enable ROM space decodes */
 145         if (pci_enable_rom(pdev))
 146                 return NULL;
 147
 148         rom = ioremap(start, *size);
 149         if (!rom)
 150                 goto err_ioremap;
 151
 152         /*
 153          * Try to find the true size of the ROM since sometimes the PCI window
 154          * size is much larger than the actual size of the ROM.
 155          * True size is important if the ROM is going to be copied.
 156          */
 157         *size = pci_get_rom_size(pdev, rom, *size);
 158         if (!*size)
 159                 goto invalid_rom;
 160
 161         return rom;
 162
 163 invalid_rom:
 164         iounmap(rom);
 165 err_ioremap:
 166         /* restore enable if ioremap fails */
 167         if (!(res->flags & IORESOURCE_ROM_ENABLE))
 168                 pci_disable_rom(pdev);
 169         return NULL;
 170 }
 171 EXPORT_SYMBOL(pci_map_rom);
 172
 173 /**
 174  * pci_unmap_rom - unmap the ROM from kernel space
 175  * @pdev: pointer to pci device struct
 176  * @rom: virtual address of the previous mapping
 177  *
 178  * Remove a mapping of a previously mapped ROM
 179  */
 180 void pci_unmap_rom(struct pci_dev *pdev, void __iomem *rom)
 181 {
 182         struct resource *res = &pdev->resource[PCI_ROM_RESOURCE];
 183
 184         iounmap(rom);
 185
 186         /* Disable again before continuing */
 187         if (!(res->flags & IORESOURCE_ROM_ENABLE))
 188                 pci_disable_rom(pdev);
 189 }
 190 EXPORT_SYMBOL(pci_unmap_rom);
 191
 192 /**
 193  * pci_platform_rom - provides a pointer to any ROM image provided by the
 194  * platform
 195  * @pdev: pointer to pci device struct
 196  * @size: pointer to receive size of pci window over ROM
 197  */
 198 void __iomem *pci_platform_rom(struct pci_dev *pdev, size_t *size)
 199 {
 200         if (pdev->rom && pdev->romlen) {
 201                 *size = pdev->romlen;
 202                 return phys_to_virt((phys_addr_t)pdev->rom);
 203         }
 204
 205         return NULL;
 206 }
 207 EXPORT_SYMBOL(pci_platform_rom);