x86: acpi: Add wake up assembly stub

This adds a wake up stub before jumping to OS wake up vector.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Stefan Roese <sr@denx.de>

arch/x86/cpu/Makefile

@@ -45,6 +45,7 @@ ifndef CONFIG_$(SPL_)X86_64
 obj-$(CONFIG_SMP) += sipi_vector.o
 endif
 obj-y += turbo.o
+obj-$(CONFIG_HAVE_ACPI_RESUME) += wakeup.o
 
 ifeq ($(CONFIG_$(SPL_)X86_64),y)
 obj-y += x86_64/

arch/x86/cpu/wakeup.S

+/*
+ * Copyright (C) 2017, Bin Meng <bmeng.cn@gmail.com>
+ *
+ * From coreboot src/arch/x86/wakeup.S
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <asm/acpi_s3.h>
+#include <asm/processor.h>
+#include <asm/processor-flags.h>
+
+#define RELOCATED(x)	((x) - __wakeup + WAKEUP_BASE)
+
+#define CODE_SEG	(X86_GDT_ENTRY_16BIT_CS * X86_GDT_ENTRY_SIZE)
+#define DATA_SEG	(X86_GDT_ENTRY_16BIT_DS * X86_GDT_ENTRY_SIZE)
+
+	.code32
+	.globl __wakeup
+__wakeup:
+	/* First prepare the jmp to the resume vector */
+	mov	0x4(%esp), %eax	/* vector */
+	/* last 4 bits of linear addr are taken as offset */
+	andw	$0x0f, %ax
+	movw	%ax, (__wakeup_offset)
+	mov	0x4(%esp), %eax
+	/* the rest is taken as segment */
+	shr	$4, %eax
+	movw	%ax, (__wakeup_segment)
+
+	/* Activate the right segment descriptor real mode */
+	ljmp	$CODE_SEG, $RELOCATED(1f)
+1:
+	/* 16 bit code from here on... */
+	.code16
+
+	/*
+	 * Load the segment registers w/ properly configured segment
+	 * descriptors. They will retain these configurations (limits,
+	 * writability, etc.) once protected mode is turned off.
+	 */
+	mov	$DATA_SEG, %ax
+	mov	%ax, %ds
+	mov	%ax, %es
+	mov	%ax, %fs
+	mov	%ax, %gs
+	mov	%ax, %ss
+
+	/* Turn off protection */
+	movl	%cr0, %eax
+	andl	$~X86_CR0_PE, %eax
+	movl	%eax, %cr0
+
+	/* Now really going into real mode */
+	ljmp	$0, $RELOCATED(1f)
+1:
+	movw	$0x0, %ax
+	movw	%ax, %ds
+	movw	%ax, %es
+	movw	%ax, %ss
+	movw	%ax, %fs
+	movw	%ax, %gs
+
+	/*
+	 * This is a FAR JMP to the OS waking vector.
+	 * The C code changes the address to be correct.
+	 */
+	.byte 0xea
+
+__wakeup_offset = RELOCATED(.)
+	.word 0x0000
+
+__wakeup_segment = RELOCATED(.)
+	.word 0x0000
+
+	.globl __wakeup_size
+__wakeup_size:
+	.long . - __wakeup

arch/x86/include/asm/acpi_s3.h

@@ -7,6 +7,8 @@
 #ifndef __ASM_ACPI_S3_H__
 #define __ASM_ACPI_S3_H__
 
+#define WAKEUP_BASE	0x600
+
 /* PM1_STATUS register */
 #define WAK_STS		(1 << 15)
 #define PCIEXPWAK_STS	(1 << 14)
@@ -27,6 +29,11 @@
 #define SLP_TYP_S4	6
 #define SLP_TYP_S5	7
 
+#ifndef __ASSEMBLY__
+
+extern char __wakeup[];
+extern int __wakeup_size;
+
 enum acpi_sleep_state {
 	ACPI_S0,
 	ACPI_S1,
@@ -92,4 +99,6 @@ enum acpi_sleep_state chipset_prev_sleep_state(void);
  */
 void chipset_clear_sleep_state(void);
 
+#endif /* __ASSEMBLY__ */
+
 #endif /* __ASM_ACPI_S3_H__ */