1 /* 2 * Copyright (C) 2017, Bin Meng <bmeng.cn@gmail.com> 3 * 4 * SPDX-License-Identifier: GPL-2.0+ 5 */ 6 7 #include <common.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 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 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 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