/******************************************************************************
   *
   * Module Name: tbxfroot - Find the root ACPI table (RSDT)
   *
   *****************************************************************************/
  
  /*

   * Copyright (C) 2000 - 2008, Intel Corp.

   * All rights reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions, and the following disclaimer,
   *    without modification.
   * 2. Redistributions in binary form must reproduce at minimum a disclaimer
   *    substantially similar to the "NO WARRANTY" disclaimer below
   *    ("Disclaimer") and any redistribution must be conditioned upon
   *    including a substantially similar Disclaimer requirement for further
   *    binary redistribution.
   * 3. Neither the names of the above-listed copyright holders nor the names
   *    of any contributors may be used to endorse or promote products derived
   *    from this software without specific prior written permission.
   *
   * Alternatively, this software may be distributed under the terms of the
   * GNU General Public License ("GPL") version 2 as published by the Free
   * Software Foundation.
   *
   * NO WARRANTY
   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
   * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
   * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
   * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
   * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   * POSSIBILITY OF SUCH DAMAGES.
   */

  #include <acpi/acpi.h>

  #include "accommon.h"
  #include "actables.h"

  #define _COMPONENT          ACPI_TABLES

  ACPI_MODULE_NAME("tbxfroot")

  /* Local prototypes */

  static u8 *acpi_tb_scan_memory_for_rsdp(u8 * start_address, u32 length);

  static acpi_status acpi_tb_validate_rsdp(struct acpi_table_rsdp *rsdp);

  /*******************************************************************************
   *

   * FUNCTION:    acpi_tb_validate_rsdp
   *

   * PARAMETERS:  Rsdp                - Pointer to unvalidated RSDP

   *
   * RETURN:      Status
   *
   * DESCRIPTION: Validate the RSDP (ptr)
   *
   ******************************************************************************/

  static acpi_status acpi_tb_validate_rsdp(struct acpi_table_rsdp *rsdp)

  {

  	ACPI_FUNCTION_ENTRY();

  
  	/*

  	 * The signature and checksum must both be correct
  	 *
  	 * Note: Sometimes there exists more than one RSDP in memory; the valid
  	 * RSDP has a valid checksum, all others have an invalid checksum.

  	 */

  	if (ACPI_STRNCMP((char *)rsdp, ACPI_SIG_RSDP,
  			 sizeof(ACPI_SIG_RSDP) - 1) != 0) {

  		/* Nope, BAD Signature */
  
  		return (AE_BAD_SIGNATURE);
  	}
  
  	/* Check the standard checksum */

  	if (acpi_tb_checksum((u8 *) rsdp, ACPI_RSDP_CHECKSUM_LENGTH) != 0) {

  		return (AE_BAD_CHECKSUM);
  	}
  
  	/* Check extended checksum if table version >= 2 */
  
  	if ((rsdp->revision >= 2) &&

  	    (acpi_tb_checksum((u8 *) rsdp, ACPI_RSDP_XCHECKSUM_LENGTH) != 0)) {

  		return (AE_BAD_CHECKSUM);
  	}
  
  	return (AE_OK);
  }

  /*******************************************************************************
   *

   * FUNCTION:    acpi_find_root_pointer

   *

   * PARAMETERS:  table_address           - Where the table pointer is returned

   *

   * RETURN:      Status, RSDP physical address

   *

   * DESCRIPTION: Search lower 1_mbyte of memory for the root system descriptor
   *              pointer structure.  If it is found, set *RSDP to point to it.

   *

   * NOTE1:       The RSDP must be either in the first 1_k of the Extended
   *              BIOS Data Area or between E0000 and FFFFF (From ACPI Spec.)
   *              Only a 32-bit physical address is necessary.

   *

   * NOTE2:       This function is always available, regardless of the
   *              initialization state of the rest of ACPI.

   *
   ******************************************************************************/

  acpi_status acpi_find_root_pointer(acpi_size *table_address)

  {

  	u8 *table_ptr;
  	u8 *mem_rover;
  	u32 physical_address;

  	ACPI_FUNCTION_TRACE(acpi_find_root_pointer);

  	/* 1a) Get the location of the Extended BIOS Data Area (EBDA) */

  	table_ptr = acpi_os_map_memory((acpi_physical_address)
  				       ACPI_EBDA_PTR_LOCATION,
  				       ACPI_EBDA_PTR_LENGTH);
  	if (!table_ptr) {
  		ACPI_ERROR((AE_INFO,
  			    "Could not map memory at %8.8X for length %X",
  			    ACPI_EBDA_PTR_LOCATION, ACPI_EBDA_PTR_LENGTH));

  		return_ACPI_STATUS(AE_NO_MEMORY);

  	}

  	ACPI_MOVE_16_TO_32(&physical_address, table_ptr);

  	/* Convert segment part to physical address */

  	physical_address <<= 4;
  	acpi_os_unmap_memory(table_ptr, ACPI_EBDA_PTR_LENGTH);

  	/* EBDA present? */

  	if (physical_address > 0x400) {

  		/*

  		 * 1b) Search EBDA paragraphs (EBDA is required to be a
  		 *     minimum of 1_k length)

  		 */

  		table_ptr = acpi_os_map_memory((acpi_physical_address)

  					       physical_address,
  					       ACPI_EBDA_WINDOW_SIZE);
  		if (!table_ptr) {
  			ACPI_ERROR((AE_INFO,
  				    "Could not map memory at %8.8X for length %X",
  				    physical_address, ACPI_EBDA_WINDOW_SIZE));

  			return_ACPI_STATUS(AE_NO_MEMORY);

  		}

  		mem_rover =
  		    acpi_tb_scan_memory_for_rsdp(table_ptr,
  						 ACPI_EBDA_WINDOW_SIZE);
  		acpi_os_unmap_memory(table_ptr, ACPI_EBDA_WINDOW_SIZE);

  		if (mem_rover) {

  			/* Return the physical address */

  			physical_address +=
  			    (u32) ACPI_PTR_DIFF(mem_rover, table_ptr);

  			*table_address = physical_address;
  			return_ACPI_STATUS(AE_OK);

  		}
  	}

  	/*
  	 * 2) Search upper memory: 16-byte boundaries in E0000h-FFFFFh
  	 */
  	table_ptr = acpi_os_map_memory((acpi_physical_address)
  				       ACPI_HI_RSDP_WINDOW_BASE,
  				       ACPI_HI_RSDP_WINDOW_SIZE);

  	if (!table_ptr) {
  		ACPI_ERROR((AE_INFO,
  			    "Could not map memory at %8.8X for length %X",
  			    ACPI_HI_RSDP_WINDOW_BASE,
  			    ACPI_HI_RSDP_WINDOW_SIZE));

  		return_ACPI_STATUS(AE_NO_MEMORY);

  	}

  	mem_rover =
  	    acpi_tb_scan_memory_for_rsdp(table_ptr, ACPI_HI_RSDP_WINDOW_SIZE);
  	acpi_os_unmap_memory(table_ptr, ACPI_HI_RSDP_WINDOW_SIZE);

  	if (mem_rover) {

  		/* Return the physical address */

  		physical_address = (u32)
  		    (ACPI_HI_RSDP_WINDOW_BASE +
  		     ACPI_PTR_DIFF(mem_rover, table_ptr));

  		*table_address = physical_address;
  		return_ACPI_STATUS(AE_OK);

  	}

  	/* A valid RSDP was not found */
  
  	ACPI_ERROR((AE_INFO, "A valid RSDP was not found"));
  	return_ACPI_STATUS(AE_NOT_FOUND);

  }

  /*******************************************************************************
   *
   * FUNCTION:    acpi_tb_scan_memory_for_rsdp
   *
   * PARAMETERS:  start_address       - Starting pointer for search
   *              Length              - Maximum length to search
   *
   * RETURN:      Pointer to the RSDP if found, otherwise NULL.
   *
   * DESCRIPTION: Search a block of memory for the RSDP signature
   *
   ******************************************************************************/

  static u8 *acpi_tb_scan_memory_for_rsdp(u8 * start_address, u32 length)

  {

  	acpi_status status;
  	u8 *mem_rover;
  	u8 *end_address;

  	ACPI_FUNCTION_TRACE(tb_scan_memory_for_rsdp);

  
  	end_address = start_address + length;
  
  	/* Search from given start address for the requested length */
  
  	for (mem_rover = start_address; mem_rover < end_address;

  	     mem_rover += ACPI_RSDP_SCAN_STEP) {

  		/* The RSDP signature and checksum must both be correct */

  		status =
  		    acpi_tb_validate_rsdp(ACPI_CAST_PTR

  					  (struct acpi_table_rsdp, mem_rover));

  		if (ACPI_SUCCESS(status)) {

  			/* Sig and checksum valid, we have found a real RSDP */

  			ACPI_DEBUG_PRINT((ACPI_DB_INFO,
  					  "RSDP located at physical address %p
  ",
  					  mem_rover));
  			return_PTR(mem_rover);

  		}

  		/* No sig match or bad checksum, keep searching */

  	}
  
  	/* Searched entire block, no RSDP was found */

  	ACPI_DEBUG_PRINT((ACPI_DB_INFO,
  			  "Searched entire block from %p, valid RSDP was not found
  ",
  			  start_address));
  	return_PTR(NULL);

  }