src/arch/x86/ebda.c

   1 /* SPDX-License-Identifier: GPL-2.0-only */
   2
   3 #include <stdint.h>
   4 #include <acpi/acpi.h>
   5 #include <arch/ebda.h>
   6 #include <commonlib/endian.h>
   7
   8 static void *get_ebda_start(void)
   9 {
  10         return (void *)((uintptr_t)DEFAULT_EBDA_SEGMENT << 4);
  11 }
  12
  13 /*
  14  * EBDA area is representing a 1KB memory area just below
  15  * the top of conventional memory (below 1MB)
  16  */
  17
  18 static void setup_ebda(u32 low_memory_size, u16 ebda_segment, u16 ebda_size)
  19 {
  20         u16 low_memory_kb;
  21         u16 ebda_kb;
  22         void *ebda;
  23
  24         if (!low_memory_size || !ebda_segment || !ebda_size)
  25                 return;
  26
  27         low_memory_kb = low_memory_size >> 10;
  28         ebda_kb = ebda_size >> 10;
  29         ebda = get_ebda_start();
  30
  31         /* clear BIOS DATA AREA */
  32         zero_n(X86_BDA_BASE, X86_BDA_SIZE);
  33
  34         /* Avoid unaligned write16() since it's undefined behavior */
  35         write_le16(X86_EBDA_LOWMEM, low_memory_kb);
  36         write_le16(X86_EBDA_SEGMENT, ebda_segment);
  37
  38         /* Set up EBDA */
  39         zero_n(ebda, ebda_size);
  40         write_le16(ebda, ebda_kb);
  41 }
  42
  43 void setup_default_ebda(void)
  44 {
  45         if (acpi_is_wakeup_s3())
  46                 return;
  47
  48         setup_ebda(DEFAULT_EBDA_LOWMEM,
  49                    DEFAULT_EBDA_SEGMENT,
  50                    DEFAULT_EBDA_SIZE);
  51 }