1 /* SPDX-License-Identifier: GPL-2.0-only */
2
3 #include <acpi/acpi.h>
4 #include <bootstate.h>
5 #include <commonlib/endian.h>
6 #include <types.h>
7
8 #define X86_BDA_SIZE 0x200
9 #define X86_BDA_BASE ((void *)0x400)
10 #define X86_EBDA_SEGMENT ((void *)0x40e)
11 #define X86_EBDA_LOWMEM ((void *)0x413)
12
13 #define DEFAULT_EBDA_LOWMEM (1024 << 10)
14 #define DEFAULT_EBDA_SEGMENT 0xF600
15 #define DEFAULT_EBDA_SIZE 0x400
16
17
get_ebda_start(void)18 static void *get_ebda_start(void)
19 {
20 return (void *)((uintptr_t)DEFAULT_EBDA_SEGMENT << 4);
21 }
22
23 /*
24 * EBDA area is representing a 1KB memory area just below
25 * the top of conventional memory (below 1MB)
26 */
27
setup_ebda(u32 low_memory_size,u16 ebda_segment,u16 ebda_size)28 static void setup_ebda(u32 low_memory_size, u16 ebda_segment, u16 ebda_size)
29 {
30 u16 low_memory_kb;
31 u16 ebda_kb;
32 void *ebda;
33
34 if (!low_memory_size || !ebda_segment || !ebda_size)
35 return;
36
37 low_memory_kb = low_memory_size >> 10;
38 ebda_kb = ebda_size >> 10;
39 ebda = get_ebda_start();
40
41 /* clear BIOS DATA AREA */
42 zero_n(X86_BDA_BASE, X86_BDA_SIZE);
43
44 /* Avoid unaligned write16() since it's undefined behavior */
45 write_le16(X86_EBDA_LOWMEM, low_memory_kb);
46 write_le16(X86_EBDA_SEGMENT, ebda_segment);
47
48 /* Set up EBDA */
49 zero_n(ebda, ebda_size);
50 write_le16(ebda, ebda_kb);
51 }
52
setup_default_ebda(void * unused)53 static void setup_default_ebda(void *unused)
54 {
55 if (acpi_is_wakeup_s3())
56 return;
57
58 setup_ebda(DEFAULT_EBDA_LOWMEM,
59 DEFAULT_EBDA_SEGMENT,
60 DEFAULT_EBDA_SIZE);
61 }
62
63 /* Ensure EBDA is prepared before Option ROMs. */
64 BOOT_STATE_INIT_ENTRY(BS_DEV_INIT, BS_ON_ENTRY, setup_default_ebda, NULL);
65