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 */
24int 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(bus: pdev->bus, region: &region, res);
43 pci_read_config_dword(dev: pdev, where: pdev->rom_base_reg, val: &rom_addr);
44 rom_addr &= ~PCI_ROM_ADDRESS_MASK;
45 rom_addr |= region.start | PCI_ROM_ADDRESS_ENABLE;
46 pci_write_config_dword(dev: pdev, where: pdev->rom_base_reg, val: rom_addr);
47 return 0;
48}
49EXPORT_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 */
58void 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(dev: pdev, where: pdev->rom_base_reg, val: &rom_addr);
67 rom_addr &= ~PCI_ROM_ADDRESS_ENABLE;
68 pci_write_config_dword(dev: pdev, where: pdev->rom_base_reg, val: rom_addr);
69}
70EXPORT_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 */
83static 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 int 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(addr: 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(addr: image + 24);
101 if (readl(addr: 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(addr: pds + 21) & 0x80;
107 length = readw(addr: 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(addr: 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 */
136void __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(dev: pdev, i: 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(offset: start, size: *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: *size);
165 if (!*size)
166 goto invalid_rom;
167
168 return rom;
169
170invalid_rom:
171 iounmap(addr: rom);
172err_ioremap:
173 /* restore enable if ioremap fails */
174 if (!(res->flags & IORESOURCE_ROM_ENABLE))
175 pci_disable_rom(pdev);
176 return NULL;
177}
178EXPORT_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 */
187void pci_unmap_rom(struct pci_dev *pdev, void __iomem *rom)
188{
189 struct resource *res = &pdev->resource[PCI_ROM_RESOURCE];
190
191 iounmap(addr: rom);
192
193 /* Disable again before continuing */
194 if (!(res->flags & IORESOURCE_ROM_ENABLE))
195 pci_disable_rom(pdev);
196}
197EXPORT_SYMBOL(pci_unmap_rom);
198