1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * Copyright (C) 2017, Bin Meng <bmeng.cn@gmail.com>
4 */
5
6 #include <common.h>
7 #include <asm/acpi.h>
8 #include <asm/acpi_s3.h>
9 #include <asm/acpi_table.h>
10 #include <asm/post.h>
11 #include <linux/linkage.h>
12
13 DECLARE_GLOBAL_DATA_PTR;
14
15 static void asmlinkage (*acpi_do_wakeup)(void *vector) = (void *)WAKEUP_BASE;
16
acpi_jump_to_wakeup(void * vector)17 static void acpi_jump_to_wakeup(void *vector)
18 {
19 /* Copy wakeup trampoline in place */
20 memcpy((void *)WAKEUP_BASE, __wakeup, __wakeup_size);
21
22 printf("Jumping to OS waking vector %p\n", vector);
23 acpi_do_wakeup(vector);
24 }
25
acpi_resume(struct acpi_fadt * fadt)26 void acpi_resume(struct acpi_fadt *fadt)
27 {
28 void *wake_vec;
29
30 /* Turn on ACPI mode for S3 */
31 enter_acpi_mode(fadt->pm1a_cnt_blk);
32
33 wake_vec = acpi_find_wakeup_vector(fadt);
34
35 /*
36 * Restore the memory content starting from address 0x1000 which is
37 * used for the real mode interrupt handler stubs.
38 */
39 memcpy((void *)0x1000, (const void *)gd->arch.backup_mem,
40 S3_RESERVE_SIZE);
41
42 post_code(POST_OS_RESUME);
43 acpi_jump_to_wakeup(wake_vec);
44 }
45
acpi_s3_reserve(void)46 int acpi_s3_reserve(void)
47 {
48 /* adjust stack pointer for ACPI S3 resume backup memory */
49 gd->start_addr_sp -= S3_RESERVE_SIZE;
50 gd->arch.backup_mem = gd->start_addr_sp;
51
52 gd->start_addr_sp &= ~0xf;
53
54 /*
55 * U-Boot sets up the real mode interrupt handler stubs starting from
56 * address 0x1000. In most cases, the first 640K (0x00000 - 0x9ffff)
57 * system memory is reported as system RAM in E820 table to the OS.
58 * (see install_e820_map() implementation for each platform). So OS
59 * can use these memories whatever it wants.
60 *
61 * If U-Boot is in an S3 resume path, care must be taken not to corrupt
62 * these memorie otherwise OS data gets lost. Testing shows that, on
63 * Microsoft Windows 10 on Intel Baytrail its wake up vector happens to
64 * be installed at the same address 0x1000. While on Linux its wake up
65 * vector does not overlap this memory range, but after resume kernel
66 * checks low memory range per config option CONFIG_X86_RESERVE_LOW
67 * which is 64K by default to see whether a memory corruption occurs
68 * during the suspend/resume (it's harmless, but warnings are shown
69 * in the kernel dmesg logs).
70 *
71 * We cannot simply mark the these memory as reserved in E820 table
72 * because such configuration makes GRUB complain: unable to allocate
73 * real mode page. Hence we choose to back up these memories to the
74 * place where we reserved on our stack for our S3 resume work.
75 * Before jumping to OS wake up vector, we need restore the original
76 * content there (see acpi_resume() above).
77 */
78 if (gd->arch.prev_sleep_state == ACPI_S3)
79 memcpy((void *)gd->arch.backup_mem, (const void *)0x1000,
80 S3_RESERVE_SIZE);
81
82 return 0;
83 }
84