ebda.c

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/* SPDX-License-Identifier: GPL-2.0-only */
 
#include <stdint.h>
#include <acpi/acpi.h>
#include <arch/ebda.h>
#include <commonlib/endian.h>
 
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);
}
 
void setup_default_ebda(void)
{
        if (acpi_is_wakeup_s3())
                return;
 
        setup_ebda(DEFAULT_EBDA_LOWMEM,
                   DEFAULT_EBDA_SEGMENT,
                   DEFAULT_EBDA_SIZE);
}