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  */
pci_enable_rom(struct pci_dev * pdev)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  */
pci_disable_rom(struct pci_dev * pdev)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  */
pci_get_rom_size(struct pci_dev * pdev,void __iomem * rom,size_t size)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  */
pci_map_rom(struct pci_dev * pdev,size_t * size)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  */
pci_unmap_rom(struct pci_dev * pdev,void __iomem * rom)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