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