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/* SPDX-License-Identifier: GPL-2.0-only */
#include <acpi/acpi.h>
#include <bootstate.h>
#include <commonlib/endian.h>
#include <stdint.h>
#define X86_BDA_SIZE 0x200
#define X86_BDA_BASE ((void *)0x400)
#define X86_EBDA_SEGMENT ((void *)0x40e)
#define X86_EBDA_LOWMEM ((void *)0x413)
#define DEFAULT_EBDA_LOWMEM (1024 << 10)
#define DEFAULT_EBDA_SEGMENT 0xF600
#define DEFAULT_EBDA_SIZE 0x400
static void *get_ebda_start(void)
{
return (void *)((uintptr_t)DEFAULT_EBDA_SEGMENT << 4);
}
/*
* EBDA area is representing a 1KB memory area just below
* the top of conventional memory (below 1MB)
*/
static void setup_ebda(u32 low_memory_size, u16 ebda_segment, u16 ebda_size)
{
u16 low_memory_kb;
u16 ebda_kb;
void *ebda;
if (!low_memory_size || !ebda_segment || !ebda_size)
return;
low_memory_kb = low_memory_size >> 10;
ebda_kb = ebda_size >> 10;
ebda = get_ebda_start();
/* clear BIOS DATA AREA */
zero_n(X86_BDA_BASE, X86_BDA_SIZE);
/* Avoid unaligned write16() since it's undefined behavior */
write_le16(X86_EBDA_LOWMEM, low_memory_kb);
write_le16(X86_EBDA_SEGMENT, ebda_segment);
/* Set up EBDA */
zero_n(ebda, ebda_size);
write_le16(ebda, ebda_kb);
}
static void setup_default_ebda(void *unused)
{
if (acpi_is_wakeup_s3())
return;
setup_ebda(DEFAULT_EBDA_LOWMEM,
DEFAULT_EBDA_SEGMENT,
DEFAULT_EBDA_SIZE);
}
/* Ensure EBDA is prepared before Option ROMs. */
BOOT_STATE_INIT_ENTRY(BS_DEV_INIT, BS_ON_ENTRY, setup_default_ebda, NULL);
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