drivers/bus/acpi/tables/tbxfroot.c

   1 /******************************************************************************
   2  *
   3  * Module Name: tbxfroot - Find the root ACPI table (RSDT)
   4  *              $Revision$
   5  *
   6  *****************************************************************************/
   7
   8 /*
   9  *  Copyright (C) 2000, 2001 R. Byron Moore
  10  *
  11  *  This program is free software; you can redistribute it and/or modify
  12  *  it under the terms of the GNU General Public License as published by
  13  *  the Free Software Foundation; either version 2 of the License, or
  14  *  (at your option) any later version.
  15  *
  16  *  This program is distributed in the hope that it will be useful,
  17  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  *  GNU General Public License for more details.
  20  *
  21  *  You should have received a copy of the GNU General Public License
  22  *  along with this program; if not, write to the Free Software
  23  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  24  */
  25
  26
  27 #include "acpi.h"
  28 #include "achware.h"
  29 #include "actables.h"
  30
  31
  32 #define _COMPONENT          ACPI_TABLES
  33          MODULE_NAME         ("tbxfroot")
  34
  35 #define RSDP_CHECKSUM_LENGTH 20
  36
  37
  38 /*******************************************************************************
  39  *
  40  * FUNCTION:    Acpi_find_root_pointer
  41  *
  42  * PARAMETERS:  **Rsdp_physical_address     - Where to place the RSDP address
  43  *
  44  * RETURN:      Status, Physical address of the RSDP
  45  *
  46  * DESCRIPTION: Find the RSDP
  47  *
  48  ******************************************************************************/
  49
  50 ACPI_STATUS
  51 acpi_find_root_pointer (
  52         ACPI_PHYSICAL_ADDRESS   *rsdp_physical_address)
  53 {
  54         ACPI_TABLE_DESC         table_info;
  55         ACPI_STATUS             status;
  56
  57
  58         /* Get the RSDP */
  59
  60         status = acpi_tb_find_rsdp (&table_info);
  61         if (ACPI_FAILURE (status)) {
  62                 return (AE_NO_ACPI_TABLES);
  63         }
  64
  65         *rsdp_physical_address = table_info.physical_address;
  66
  67         return (AE_OK);
  68 }
  69
  70
  71 /*******************************************************************************
  72  *
  73  * FUNCTION:    Acpi_tb_scan_memory_for_rsdp
  74  *
  75  * PARAMETERS:  Start_address       - Starting pointer for search
  76  *              Length              - Maximum length to search
  77  *
  78  * RETURN:      Pointer to the RSDP if found, otherwise NULL.
  79  *
  80  * DESCRIPTION: Search a block of memory for the RSDP signature
  81  *
  82  ******************************************************************************/
  83
  84 u8 *
  85 acpi_tb_scan_memory_for_rsdp (
  86         u8                      *start_address,
  87         u32                     length)
  88 {
  89         u32                     offset;
  90         u8                      *mem_rover;
  91
  92
  93         /* Search from given start addr for the requested length  */
  94
  95         for (offset = 0, mem_rover = start_address;
  96                  offset < length;
  97                  offset += RSDP_SCAN_STEP, mem_rover += RSDP_SCAN_STEP) {
  98
  99                 /* The signature and checksum must both be correct */
 100
 101                 if (STRNCMP ((NATIVE_CHAR *) mem_rover,
 102                                 RSDP_SIG, sizeof (RSDP_SIG)-1) == 0 &&
 103                         acpi_tb_checksum (mem_rover, RSDP_CHECKSUM_LENGTH) == 0) {
 104                         /* If so, we have found the RSDP */
 105
 106                         return (mem_rover);
 107                 }
 108         }
 109
 110         /* Searched entire block, no RSDP was found */
 111
 112         return (NULL);
 113 }
 114
 115
 116 /*******************************************************************************
 117  *
 118  * FUNCTION:    Acpi_tb_find_rsdp
 119  *
 120  * PARAMETERS:  *Buffer_ptr             - If == NULL, read data from buffer
 121  *                                        rather than searching memory
 122  *              *Table_info             - Where the table info is returned
 123  *
 124  * RETURN:      Status
 125  *
 126  * DESCRIPTION: Search lower 1_mbyte of memory for the root system descriptor
 127  *              pointer structure.  If it is found, set *RSDP to point to it.
 128  *
 129  *              NOTE: The RSDP must be either in the first 1_k of the Extended
 130  *              BIOS Data Area or between E0000 and FFFFF (ACPI 1.0 section
 131  *              5.2.2; assertion #421).
 132  *
 133  ******************************************************************************/
 134
 135 ACPI_STATUS
 136 acpi_tb_find_rsdp (
 137         ACPI_TABLE_DESC         *table_info)
 138 {
 139         u8                      *table_ptr;
 140         u8                      *mem_rover;
 141         UINT64                  phys_addr;
 142         ACPI_STATUS             status = AE_OK;
 143
 144
 145         /*
 146          * Search memory for RSDP.  First map low physical memory.
 147          */
 148
 149         status = acpi_os_map_memory (LO_RSDP_WINDOW_BASE, LO_RSDP_WINDOW_SIZE,
 150                           (void **)&table_ptr);
 151
 152         if (ACPI_FAILURE (status)) {
 153                 return (status);
 154         }
 155
 156         /*
 157          * 1) Search EBDA (low memory) paragraphs
 158          */
 159
 160         mem_rover = acpi_tb_scan_memory_for_rsdp (table_ptr, LO_RSDP_WINDOW_SIZE);
 161
 162         /* This mapping is no longer needed */
 163
 164         acpi_os_unmap_memory (table_ptr, LO_RSDP_WINDOW_SIZE);
 165
 166         if (mem_rover) {
 167                 /* Found it, return the physical address */
 168
 169                 phys_addr = LO_RSDP_WINDOW_BASE;
 170                 phys_addr += (mem_rover - table_ptr);
 171
 172                 table_info->physical_address = phys_addr;
 173
 174                 return (AE_OK);
 175         }
 176
 177
 178         /*
 179          * 2) Search upper memory: 16-byte boundaries in E0000h-F0000h
 180          */
 181
 182         status = acpi_os_map_memory (HI_RSDP_WINDOW_BASE, HI_RSDP_WINDOW_SIZE,
 183                           (void **)&table_ptr);
 184
 185         if (ACPI_FAILURE (status)) {
 186                 return (status);
 187         }
 188
 189         mem_rover = acpi_tb_scan_memory_for_rsdp (table_ptr, HI_RSDP_WINDOW_SIZE);
 190
 191         /* This mapping is no longer needed */
 192
 193         acpi_os_unmap_memory (table_ptr, HI_RSDP_WINDOW_SIZE);
 194
 195         if (mem_rover) {
 196                 /* Found it, return the physical address */
 197
 198                 phys_addr = HI_RSDP_WINDOW_BASE;
 199                 phys_addr += (mem_rover - table_ptr);
 200
 201                 table_info->physical_address = phys_addr;
 202
 203                 return (AE_OK);
 204         }
 205
 206
 207         /* RSDP signature was not found */
 208
 209         return (AE_NOT_FOUND);
 210 }
 211
 212