1 // SPDX-License-Identifier: GPL-2.0
2 
3 #include <linux/pci.h>
4 #include <linux/printk.h>
5 #include <linux/screen_info.h>
6 #include <linux/string.h>
7 
8 static struct pci_dev *screen_info_lfb_pdev;
9 static size_t screen_info_lfb_bar;
10 static resource_size_t screen_info_lfb_res_start; // original start of resource
11 static resource_size_t screen_info_lfb_offset; // framebuffer offset within resource
12 
13 static bool __screen_info_relocation_is_valid(const struct screen_info *si, struct resource *pr)
14 {
15 	u64 size = __screen_info_lfb_size(si, screen_info_video_type(si));
16 
17 	if (screen_info_lfb_offset > resource_size(pr))
18 		return false;
19 	if (size > resource_size(pr))
20 		return false;
21 	if (resource_size(pr) - size < screen_info_lfb_offset)
22 		return false;
23 
24 	return true;
25 }
26 
27 void screen_info_apply_fixups(void)
28 {
29 	struct screen_info *si = &screen_info;
30 
31 	if (screen_info_lfb_pdev) {
32 		struct resource *pr = &screen_info_lfb_pdev->resource[screen_info_lfb_bar];
33 
34 		if (pr->start != screen_info_lfb_res_start) {
35 			if (__screen_info_relocation_is_valid(si, pr)) {
36 				/*
37 				 * Only update base if we have an actual
38 				 * relocation to a valid I/O range.
39 				 */
40 				__screen_info_set_lfb_base(si, pr->start + screen_info_lfb_offset);
41 				pr_info("Relocating firmware framebuffer to offset %pa[d] within %pr\n",
42 					&screen_info_lfb_offset, pr);
43 			} else {
44 				pr_warn("Invalid relocating, disabling firmware framebuffer\n");
45 			}
46 		}
47 	}
48 }
49 
50 static int __screen_info_lfb_pci_bus_region(const struct screen_info *si, unsigned int type,
51 					    struct pci_bus_region *r)
52 {
53 	u64 base, size;
54 
55 	base = __screen_info_lfb_base(si);
56 	if (!base)
57 		return -EINVAL;
58 
59 	size = __screen_info_lfb_size(si, type);
60 	if (!size)
61 		return -EINVAL;
62 
63 	r->start = base;
64 	r->end = base + size - 1;
65 
66 	return 0;
67 }
68 
69 static void screen_info_fixup_lfb(struct pci_dev *pdev)
70 {
71 	unsigned int type;
72 	struct pci_bus_region bus_region;
73 	int ret;
74 	struct resource r = {
75 		.flags = IORESOURCE_MEM,
76 	};
77 	const struct resource *pr;
78 	const struct screen_info *si = &screen_info;
79 
80 	if (screen_info_lfb_pdev)
81 		return; // already found
82 
83 	type = screen_info_video_type(si);
84 	if (!__screen_info_has_lfb(type))
85 		return; // only applies to EFI; maybe VESA
86 
87 	ret = __screen_info_lfb_pci_bus_region(si, type, &bus_region);
88 	if (ret < 0)
89 		return;
90 
91 	/*
92 	 * Translate the PCI bus address to resource. Account
93 	 * for an offset if the framebuffer is behind a PCI host
94 	 * bridge.
95 	 */
96 	pcibios_bus_to_resource(pdev->bus, &r, &bus_region);
97 
98 	pr = pci_find_resource(pdev, &r);
99 	if (!pr)
100 		return;
101 
102 	/*
103 	 * We've found a PCI device with the framebuffer
104 	 * resource. Store away the parameters to track
105 	 * relocation of the framebuffer aperture.
106 	 */
107 	screen_info_lfb_pdev = pdev;
108 	screen_info_lfb_bar = pr - pdev->resource;
109 	screen_info_lfb_offset = r.start - pr->start;
110 	screen_info_lfb_res_start = bus_region.start;
111 }
112 DECLARE_PCI_FIXUP_CLASS_HEADER(PCI_ANY_ID, PCI_ANY_ID, PCI_BASE_CLASS_DISPLAY, 16,
113 			       screen_info_fixup_lfb);
114 
115 static struct pci_dev *__screen_info_pci_dev(struct resource *res)
116 {
117 	struct pci_dev *pdev = NULL;
118 	const struct resource *r = NULL;
119 
120 	if (!(res->flags & IORESOURCE_MEM))
121 		return NULL;
122 
123 	while (!r && (pdev = pci_get_base_class(PCI_BASE_CLASS_DISPLAY, pdev))) {
124 		r = pci_find_resource(pdev, res);
125 	}
126 
127 	return pdev;
128 }
129 
130 /**
131  * screen_info_pci_dev() - Return PCI parent device that contains screen_info's framebuffer
132  * @si: the screen_info
133  *
134  * Returns:
135  * The screen_info's parent device or NULL on success, or a pointer-encoded
136  * errno value otherwise. The value NULL is not an error. It signals that no
137  * PCI device has been found.
138  */
139 struct pci_dev *screen_info_pci_dev(const struct screen_info *si)
140 {
141 	struct resource res[SCREEN_INFO_MAX_RESOURCES];
142 	ssize_t i, numres;
143 
144 	numres = screen_info_resources(si, res, ARRAY_SIZE(res));
145 	if (numres < 0)
146 		return ERR_PTR(numres);
147 
148 	for (i = 0; i < numres; ++i) {
149 		struct pci_dev *pdev = __screen_info_pci_dev(&res[i]);
150 
151 		if (pdev)
152 			return pdev;
153 	}
154 
155 	return NULL;
156 }
157 EXPORT_SYMBOL(screen_info_pci_dev);
158