screen_info_pci.c

  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
  8static struct pci_dev *screen_info_lfb_pdev;
  9static size_t screen_info_lfb_bar;
 10static resource_size_t screen_info_lfb_res_start; // original start of resource
 11static resource_size_t screen_info_lfb_offset; // framebuffer offset within resource
 12
 13static 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
 27void 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
 50static 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
 69static 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}
112DECLARE_PCI_FIXUP_CLASS_HEADER(PCI_ANY_ID, PCI_ANY_ID, PCI_BASE_CLASS_DISPLAY, 16,
113			       screen_info_fixup_lfb);
114
115static 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 */
139struct 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}
157EXPORT_SYMBOL(screen_info_pci_dev);