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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_s3.h>
8 #include <asm/acpi_table.h>
9 #include <asm/post.h>
10 #include <linux/linkage.h>
11 
12 DECLARE_GLOBAL_DATA_PTR;
13 
14 static void asmlinkage (*acpi_do_wakeup)(void *vector) = (void *)WAKEUP_BASE;
15 
acpi_jump_to_wakeup(void * vector)16 static void acpi_jump_to_wakeup(void *vector)
17 {
18 	/* Copy wakeup trampoline in place */
19 	memcpy((void *)WAKEUP_BASE, __wakeup, __wakeup_size);
20 
21 	printf("Jumping to OS waking vector %p\n", vector);
22 	acpi_do_wakeup(vector);
23 }
24 
acpi_resume(struct acpi_fadt * fadt)25 void acpi_resume(struct acpi_fadt *fadt)
26 {
27 	void *wake_vec;
28 
29 	/* Turn on ACPI mode for S3 */
30 	enter_acpi_mode(fadt->pm1a_cnt_blk);
31 
32 	wake_vec = acpi_find_wakeup_vector(fadt);
33 
34 	/*
35 	 * Restore the memory content starting from address 0x1000 which is
36 	 * used for the real mode interrupt handler stubs.
37 	 */
38 	memcpy((void *)0x1000, (const void *)gd->arch.backup_mem,
39 	       S3_RESERVE_SIZE);
40 
41 	post_code(POST_OS_RESUME);
42 	acpi_jump_to_wakeup(wake_vec);
43 }
44 
acpi_s3_reserve(void)45 int acpi_s3_reserve(void)
46 {
47 	/* adjust stack pointer for ACPI S3 resume backup memory */
48 	gd->start_addr_sp -= S3_RESERVE_SIZE;
49 	gd->arch.backup_mem = gd->start_addr_sp;
50 
51 	gd->start_addr_sp &= ~0xf;
52 
53 	/*
54 	 * U-Boot sets up the real mode interrupt handler stubs starting from
55 	 * address 0x1000. In most cases, the first 640K (0x00000 - 0x9ffff)
56 	 * system memory is reported as system RAM in E820 table to the OS.
57 	 * (see install_e820_map() implementation for each platform). So OS
58 	 * can use these memories whatever it wants.
59 	 *
60 	 * If U-Boot is in an S3 resume path, care must be taken not to corrupt
61 	 * these memorie otherwise OS data gets lost. Testing shows that, on
62 	 * Microsoft Windows 10 on Intel Baytrail its wake up vector happens to
63 	 * be installed at the same address 0x1000. While on Linux its wake up
64 	 * vector does not overlap this memory range, but after resume kernel
65 	 * checks low memory range per config option CONFIG_X86_RESERVE_LOW
66 	 * which is 64K by default to see whether a memory corruption occurs
67 	 * during the suspend/resume (it's harmless, but warnings are shown
68 	 * in the kernel dmesg logs).
69 	 *
70 	 * We cannot simply mark the these memory as reserved in E820 table
71 	 * because such configuration makes GRUB complain: unable to allocate
72 	 * real mode page. Hence we choose to back up these memories to the
73 	 * place where we reserved on our stack for our S3 resume work.
74 	 * Before jumping to OS wake up vector, we need restore the original
75 	 * content there (see acpi_resume() above).
76 	 */
77 	if (gd->arch.prev_sleep_state == ACPI_S3)
78 		memcpy((void *)gd->arch.backup_mem, (const void *)0x1000,
79 		       S3_RESERVE_SIZE);
80 
81 	return 0;
82 }
83