1 /******************************************************************************
3 * Module Name: tbxfroot - Find the root ACPI table (RSDT)
5 *****************************************************************************/
8 * Copyright (C) 2000 - 2013, Intel Corp.
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44 #include <acpi/acpi.h>
48 #define _COMPONENT ACPI_TABLES
49 ACPI_MODULE_NAME("tbxfroot")
51 /*******************************************************************************
53 * FUNCTION: acpi_tb_validate_rsdp
55 * PARAMETERS: rsdp - Pointer to unvalidated RSDP
59 * DESCRIPTION: Validate the RSDP (ptr)
61 ******************************************************************************/
62 acpi_status acpi_tb_validate_rsdp(struct acpi_table_rsdp *rsdp)
66 * The signature and checksum must both be correct
68 * Note: Sometimes there exists more than one RSDP in memory; the valid
69 * RSDP has a valid checksum, all others have an invalid checksum.
71 if (ACPI_STRNCMP((char *)rsdp->signature, ACPI_SIG_RSDP,
72 sizeof(ACPI_SIG_RSDP) - 1) != 0) {
74 /* Nope, BAD Signature */
76 return (AE_BAD_SIGNATURE);
79 /* Check the standard checksum */
81 if (acpi_tb_checksum((u8 *) rsdp, ACPI_RSDP_CHECKSUM_LENGTH) != 0) {
82 return (AE_BAD_CHECKSUM);
85 /* Check extended checksum if table version >= 2 */
87 if ((rsdp->revision >= 2) &&
88 (acpi_tb_checksum((u8 *) rsdp, ACPI_RSDP_XCHECKSUM_LENGTH) != 0)) {
89 return (AE_BAD_CHECKSUM);
95 /*******************************************************************************
97 * FUNCTION: acpi_find_root_pointer
99 * PARAMETERS: table_address - Where the table pointer is returned
101 * RETURN: Status, RSDP physical address
103 * DESCRIPTION: Search lower 1Mbyte of memory for the root system descriptor
104 * pointer structure. If it is found, set *RSDP to point to it.
106 * NOTE1: The RSDP must be either in the first 1K of the Extended
107 * BIOS Data Area or between E0000 and FFFFF (From ACPI Spec.)
108 * Only a 32-bit physical address is necessary.
110 * NOTE2: This function is always available, regardless of the
111 * initialization state of the rest of ACPI.
113 ******************************************************************************/
115 acpi_status acpi_find_root_pointer(acpi_size *table_address)
119 u32 physical_address;
121 ACPI_FUNCTION_TRACE(acpi_find_root_pointer);
123 /* 1a) Get the location of the Extended BIOS Data Area (EBDA) */
125 table_ptr = acpi_os_map_memory((acpi_physical_address)
126 ACPI_EBDA_PTR_LOCATION,
127 ACPI_EBDA_PTR_LENGTH);
130 "Could not map memory at 0x%8.8X for length %u",
131 ACPI_EBDA_PTR_LOCATION, ACPI_EBDA_PTR_LENGTH));
133 return_ACPI_STATUS(AE_NO_MEMORY);
136 ACPI_MOVE_16_TO_32(&physical_address, table_ptr);
138 /* Convert segment part to physical address */
140 physical_address <<= 4;
141 acpi_os_unmap_memory(table_ptr, ACPI_EBDA_PTR_LENGTH);
145 if (physical_address > 0x400) {
147 * 1b) Search EBDA paragraphs (EBDA is required to be a
148 * minimum of 1K length)
150 table_ptr = acpi_os_map_memory((acpi_physical_address)
152 ACPI_EBDA_WINDOW_SIZE);
155 "Could not map memory at 0x%8.8X for length %u",
156 physical_address, ACPI_EBDA_WINDOW_SIZE));
158 return_ACPI_STATUS(AE_NO_MEMORY);
162 acpi_tb_scan_memory_for_rsdp(table_ptr,
163 ACPI_EBDA_WINDOW_SIZE);
164 acpi_os_unmap_memory(table_ptr, ACPI_EBDA_WINDOW_SIZE);
168 /* Return the physical address */
171 (u32) ACPI_PTR_DIFF(mem_rover, table_ptr);
173 *table_address = physical_address;
174 return_ACPI_STATUS(AE_OK);
179 * 2) Search upper memory: 16-byte boundaries in E0000h-FFFFFh
181 table_ptr = acpi_os_map_memory((acpi_physical_address)
182 ACPI_HI_RSDP_WINDOW_BASE,
183 ACPI_HI_RSDP_WINDOW_SIZE);
187 "Could not map memory at 0x%8.8X for length %u",
188 ACPI_HI_RSDP_WINDOW_BASE,
189 ACPI_HI_RSDP_WINDOW_SIZE));
191 return_ACPI_STATUS(AE_NO_MEMORY);
195 acpi_tb_scan_memory_for_rsdp(table_ptr, ACPI_HI_RSDP_WINDOW_SIZE);
196 acpi_os_unmap_memory(table_ptr, ACPI_HI_RSDP_WINDOW_SIZE);
200 /* Return the physical address */
202 physical_address = (u32)
203 (ACPI_HI_RSDP_WINDOW_BASE +
204 ACPI_PTR_DIFF(mem_rover, table_ptr));
206 *table_address = physical_address;
207 return_ACPI_STATUS(AE_OK);
210 /* A valid RSDP was not found */
212 ACPI_BIOS_ERROR((AE_INFO, "A valid RSDP was not found"));
213 return_ACPI_STATUS(AE_NOT_FOUND);
216 /*******************************************************************************
218 * FUNCTION: acpi_tb_scan_memory_for_rsdp
220 * PARAMETERS: start_address - Starting pointer for search
221 * length - Maximum length to search
223 * RETURN: Pointer to the RSDP if found, otherwise NULL.
225 * DESCRIPTION: Search a block of memory for the RSDP signature
227 ******************************************************************************/
228 u8 *acpi_tb_scan_memory_for_rsdp(u8 *start_address, u32 length)
234 ACPI_FUNCTION_TRACE(tb_scan_memory_for_rsdp);
236 end_address = start_address + length;
238 /* Search from given start address for the requested length */
240 for (mem_rover = start_address; mem_rover < end_address;
241 mem_rover += ACPI_RSDP_SCAN_STEP) {
243 /* The RSDP signature and checksum must both be correct */
246 acpi_tb_validate_rsdp(ACPI_CAST_PTR
247 (struct acpi_table_rsdp, mem_rover));
248 if (ACPI_SUCCESS(status)) {
250 /* Sig and checksum valid, we have found a real RSDP */
252 ACPI_DEBUG_PRINT((ACPI_DB_INFO,
253 "RSDP located at physical address %p\n",
255 return_PTR(mem_rover);
258 /* No sig match or bad checksum, keep searching */
261 /* Searched entire block, no RSDP was found */
263 ACPI_DEBUG_PRINT((ACPI_DB_INFO,
264 "Searched entire block from %p, valid RSDP was not found\n",