1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/ioport.h>
3 #include <asm/e820/api.h>
4
resource_clip(struct resource * res,resource_size_t start,resource_size_t end)5 static void resource_clip(struct resource *res, resource_size_t start,
6 resource_size_t end)
7 {
8 resource_size_t low = 0, high = 0;
9
10 if (res->end < start || res->start > end)
11 return; /* no conflict */
12
13 if (res->start < start)
14 low = start - res->start;
15
16 if (res->end > end)
17 high = res->end - end;
18
19 /* Keep the area above or below the conflict, whichever is larger */
20 if (low > high)
21 res->end = start - 1;
22 else
23 res->start = end + 1;
24 }
25
remove_e820_regions(struct resource * avail)26 static void remove_e820_regions(struct resource *avail)
27 {
28 int i;
29 struct e820_entry *entry;
30
31 for (i = 0; i < e820_table->nr_entries; i++) {
32 entry = &e820_table->entries[i];
33
34 resource_clip(avail, entry->addr,
35 entry->addr + entry->size - 1);
36 }
37 }
38
arch_remove_reservations(struct resource * avail)39 void arch_remove_reservations(struct resource *avail)
40 {
41 /*
42 * Trim out BIOS area (high 2MB) and E820 regions. We do not remove
43 * the low 1MB unconditionally, as this area is needed for some ISA
44 * cards requiring a memory range, e.g. the i82365 PCMCIA controller.
45 */
46 if (avail->flags & IORESOURCE_MEM) {
47 resource_clip(avail, BIOS_ROM_BASE, BIOS_ROM_END);
48
49 remove_e820_regions(avail);
50 }
51 }
52