xref: /openbmc/linux/drivers/acpi/acpica/tbxfroot.c (revision 6774def6)
1 /******************************************************************************
2  *
3  * Module Name: tbxfroot - Find the root ACPI table (RSDT)
4  *
5  *****************************************************************************/
6 
7 /*
8  * Copyright (C) 2000 - 2014, Intel Corp.
9  * All rights reserved.
10  *
11  * Redistribution and use in source and binary forms, with or without
12  * modification, are permitted provided that the following conditions
13  * are met:
14  * 1. Redistributions of source code must retain the above copyright
15  *    notice, this list of conditions, and the following disclaimer,
16  *    without modification.
17  * 2. Redistributions in binary form must reproduce at minimum a disclaimer
18  *    substantially similar to the "NO WARRANTY" disclaimer below
19  *    ("Disclaimer") and any redistribution must be conditioned upon
20  *    including a substantially similar Disclaimer requirement for further
21  *    binary redistribution.
22  * 3. Neither the names of the above-listed copyright holders nor the names
23  *    of any contributors may be used to endorse or promote products derived
24  *    from this software without specific prior written permission.
25  *
26  * Alternatively, this software may be distributed under the terms of the
27  * GNU General Public License ("GPL") version 2 as published by the Free
28  * Software Foundation.
29  *
30  * NO WARRANTY
31  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
32  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
33  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
34  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
35  * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
36  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
37  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
38  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
40  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
41  * POSSIBILITY OF SUCH DAMAGES.
42  */
43 
44 #include <acpi/acpi.h>
45 #include "accommon.h"
46 #include "actables.h"
47 
48 #define _COMPONENT          ACPI_TABLES
49 ACPI_MODULE_NAME("tbxfroot")
50 
51 /*******************************************************************************
52  *
53  * FUNCTION:    acpi_tb_get_rsdp_length
54  *
55  * PARAMETERS:  rsdp                - Pointer to RSDP
56  *
57  * RETURN:      Table length
58  *
59  * DESCRIPTION: Get the length of the RSDP
60  *
61  ******************************************************************************/
62 u32 acpi_tb_get_rsdp_length(struct acpi_table_rsdp *rsdp)
63 {
64 
65 	if (!ACPI_VALIDATE_RSDP_SIG(rsdp->signature)) {
66 
67 		/* BAD Signature */
68 
69 		return (0);
70 	}
71 
72 	/* "Length" field is available if table version >= 2 */
73 
74 	if (rsdp->revision >= 2) {
75 		return (rsdp->length);
76 	} else {
77 		return (ACPI_RSDP_CHECKSUM_LENGTH);
78 	}
79 }
80 
81 /*******************************************************************************
82  *
83  * FUNCTION:    acpi_tb_validate_rsdp
84  *
85  * PARAMETERS:  rsdp                - Pointer to unvalidated RSDP
86  *
87  * RETURN:      Status
88  *
89  * DESCRIPTION: Validate the RSDP (ptr)
90  *
91  ******************************************************************************/
92 
93 acpi_status acpi_tb_validate_rsdp(struct acpi_table_rsdp * rsdp)
94 {
95 
96 	/*
97 	 * The signature and checksum must both be correct
98 	 *
99 	 * Note: Sometimes there exists more than one RSDP in memory; the valid
100 	 * RSDP has a valid checksum, all others have an invalid checksum.
101 	 */
102 	if (!ACPI_VALIDATE_RSDP_SIG(rsdp->signature)) {
103 
104 		/* Nope, BAD Signature */
105 
106 		return (AE_BAD_SIGNATURE);
107 	}
108 
109 	/* Check the standard checksum */
110 
111 	if (acpi_tb_checksum((u8 *) rsdp, ACPI_RSDP_CHECKSUM_LENGTH) != 0) {
112 		return (AE_BAD_CHECKSUM);
113 	}
114 
115 	/* Check extended checksum if table version >= 2 */
116 
117 	if ((rsdp->revision >= 2) &&
118 	    (acpi_tb_checksum((u8 *) rsdp, ACPI_RSDP_XCHECKSUM_LENGTH) != 0)) {
119 		return (AE_BAD_CHECKSUM);
120 	}
121 
122 	return (AE_OK);
123 }
124 
125 /*******************************************************************************
126  *
127  * FUNCTION:    acpi_find_root_pointer
128  *
129  * PARAMETERS:  table_address           - Where the table pointer is returned
130  *
131  * RETURN:      Status, RSDP physical address
132  *
133  * DESCRIPTION: Search lower 1Mbyte of memory for the root system descriptor
134  *              pointer structure. If it is found, set *RSDP to point to it.
135  *
136  * NOTE1:       The RSDP must be either in the first 1K of the Extended
137  *              BIOS Data Area or between E0000 and FFFFF (From ACPI Spec.)
138  *              Only a 32-bit physical address is necessary.
139  *
140  * NOTE2:       This function is always available, regardless of the
141  *              initialization state of the rest of ACPI.
142  *
143  ******************************************************************************/
144 
145 acpi_status __init acpi_find_root_pointer(acpi_size *table_address)
146 {
147 	u8 *table_ptr;
148 	u8 *mem_rover;
149 	u32 physical_address;
150 
151 	ACPI_FUNCTION_TRACE(acpi_find_root_pointer);
152 
153 	/* 1a) Get the location of the Extended BIOS Data Area (EBDA) */
154 
155 	table_ptr = acpi_os_map_memory((acpi_physical_address)
156 				       ACPI_EBDA_PTR_LOCATION,
157 				       ACPI_EBDA_PTR_LENGTH);
158 	if (!table_ptr) {
159 		ACPI_ERROR((AE_INFO,
160 			    "Could not map memory at 0x%8.8X for length %u",
161 			    ACPI_EBDA_PTR_LOCATION, ACPI_EBDA_PTR_LENGTH));
162 
163 		return_ACPI_STATUS(AE_NO_MEMORY);
164 	}
165 
166 	ACPI_MOVE_16_TO_32(&physical_address, table_ptr);
167 
168 	/* Convert segment part to physical address */
169 
170 	physical_address <<= 4;
171 	acpi_os_unmap_memory(table_ptr, ACPI_EBDA_PTR_LENGTH);
172 
173 	/* EBDA present? */
174 
175 	if (physical_address > 0x400) {
176 		/*
177 		 * 1b) Search EBDA paragraphs (EBDA is required to be a
178 		 *     minimum of 1K length)
179 		 */
180 		table_ptr = acpi_os_map_memory((acpi_physical_address)
181 					       physical_address,
182 					       ACPI_EBDA_WINDOW_SIZE);
183 		if (!table_ptr) {
184 			ACPI_ERROR((AE_INFO,
185 				    "Could not map memory at 0x%8.8X for length %u",
186 				    physical_address, ACPI_EBDA_WINDOW_SIZE));
187 
188 			return_ACPI_STATUS(AE_NO_MEMORY);
189 		}
190 
191 		mem_rover =
192 		    acpi_tb_scan_memory_for_rsdp(table_ptr,
193 						 ACPI_EBDA_WINDOW_SIZE);
194 		acpi_os_unmap_memory(table_ptr, ACPI_EBDA_WINDOW_SIZE);
195 
196 		if (mem_rover) {
197 
198 			/* Return the physical address */
199 
200 			physical_address +=
201 			    (u32) ACPI_PTR_DIFF(mem_rover, table_ptr);
202 
203 			*table_address = physical_address;
204 			return_ACPI_STATUS(AE_OK);
205 		}
206 	}
207 
208 	/*
209 	 * 2) Search upper memory: 16-byte boundaries in E0000h-FFFFFh
210 	 */
211 	table_ptr = acpi_os_map_memory((acpi_physical_address)
212 				       ACPI_HI_RSDP_WINDOW_BASE,
213 				       ACPI_HI_RSDP_WINDOW_SIZE);
214 
215 	if (!table_ptr) {
216 		ACPI_ERROR((AE_INFO,
217 			    "Could not map memory at 0x%8.8X for length %u",
218 			    ACPI_HI_RSDP_WINDOW_BASE,
219 			    ACPI_HI_RSDP_WINDOW_SIZE));
220 
221 		return_ACPI_STATUS(AE_NO_MEMORY);
222 	}
223 
224 	mem_rover =
225 	    acpi_tb_scan_memory_for_rsdp(table_ptr, ACPI_HI_RSDP_WINDOW_SIZE);
226 	acpi_os_unmap_memory(table_ptr, ACPI_HI_RSDP_WINDOW_SIZE);
227 
228 	if (mem_rover) {
229 
230 		/* Return the physical address */
231 
232 		physical_address = (u32)
233 		    (ACPI_HI_RSDP_WINDOW_BASE +
234 		     ACPI_PTR_DIFF(mem_rover, table_ptr));
235 
236 		*table_address = physical_address;
237 		return_ACPI_STATUS(AE_OK);
238 	}
239 
240 	/* A valid RSDP was not found */
241 
242 	ACPI_BIOS_ERROR((AE_INFO, "A valid RSDP was not found"));
243 	return_ACPI_STATUS(AE_NOT_FOUND);
244 }
245 
246 /*******************************************************************************
247  *
248  * FUNCTION:    acpi_tb_scan_memory_for_rsdp
249  *
250  * PARAMETERS:  start_address       - Starting pointer for search
251  *              length              - Maximum length to search
252  *
253  * RETURN:      Pointer to the RSDP if found, otherwise NULL.
254  *
255  * DESCRIPTION: Search a block of memory for the RSDP signature
256  *
257  ******************************************************************************/
258 u8 *acpi_tb_scan_memory_for_rsdp(u8 *start_address, u32 length)
259 {
260 	acpi_status status;
261 	u8 *mem_rover;
262 	u8 *end_address;
263 
264 	ACPI_FUNCTION_TRACE(tb_scan_memory_for_rsdp);
265 
266 	end_address = start_address + length;
267 
268 	/* Search from given start address for the requested length */
269 
270 	for (mem_rover = start_address; mem_rover < end_address;
271 	     mem_rover += ACPI_RSDP_SCAN_STEP) {
272 
273 		/* The RSDP signature and checksum must both be correct */
274 
275 		status =
276 		    acpi_tb_validate_rsdp(ACPI_CAST_PTR
277 					  (struct acpi_table_rsdp, mem_rover));
278 		if (ACPI_SUCCESS(status)) {
279 
280 			/* Sig and checksum valid, we have found a real RSDP */
281 
282 			ACPI_DEBUG_PRINT((ACPI_DB_INFO,
283 					  "RSDP located at physical address %p\n",
284 					  mem_rover));
285 			return_PTR(mem_rover);
286 		}
287 
288 		/* No sig match or bad checksum, keep searching */
289 	}
290 
291 	/* Searched entire block, no RSDP was found */
292 
293 	ACPI_DEBUG_PRINT((ACPI_DB_INFO,
294 			  "Searched entire block from %p, valid RSDP was not found\n",
295 			  start_address));
296 	return_PTR(NULL);
297 }
298