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 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 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 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