ACPICA: Tables: Fix FADT dependency regression

Some logics actually relying on the existence of FADT, currently relies on
the number of loaded tables. This false dependency can easily trigger
regressions. One of them has been introduced by commit 8ec3f459073e
(ACPICA: Tables: Fix global table list issues by removing fixed table).

The commit changing the fixed table indexes results in the change of FADT
table index, originally, it was 3 (thus the installed table count should be
greater than 4), while currently it is 0 (and the installed table count may
be 3).

This patch fixes this regression by cleaning up the code. Lv Zheng.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=105351
Fixes: 8ec3f459073e (ACPICA: Tables: Fix global table list issues by removing fixed table)
Reported-and-tested-by: Meelis Roos <mroos@linux.ee>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpica/acglobal.h

@@ -61,6 +61,7 @@ ACPI_GLOBAL(struct acpi_table_header, acpi_gbl_original_dsdt_header);
 ACPI_INIT_GLOBAL(u32, acpi_gbl_dsdt_index, ACPI_INVALID_TABLE_INDEX);
 ACPI_INIT_GLOBAL(u32, acpi_gbl_facs_index, ACPI_INVALID_TABLE_INDEX);
 ACPI_INIT_GLOBAL(u32, acpi_gbl_xfacs_index, ACPI_INVALID_TABLE_INDEX);
+ACPI_INIT_GLOBAL(u32, acpi_gbl_fadt_index, ACPI_INVALID_TABLE_INDEX);
 
 #if (!ACPI_REDUCED_HARDWARE)
 ACPI_GLOBAL(struct acpi_table_facs *, acpi_gbl_FACS);

drivers/acpi/acpica/actables.h

@@ -85,7 +85,7 @@ void acpi_tb_set_table_loaded_flag(u32 table_index, u8 is_loaded);
 /*
  * tbfadt - FADT parse/convert/validate
  */
-void acpi_tb_parse_fadt(u32 table_index);
+void acpi_tb_parse_fadt(void);
 
 void acpi_tb_create_local_fadt(struct acpi_table_header *table, u32 length);
 
@@ -138,8 +138,6 @@ acpi_status acpi_tb_get_owner_id(u32 table_index, acpi_owner_id *owner_id);
  */
 acpi_status acpi_tb_initialize_facs(void);
 
-u8 acpi_tb_tables_loaded(void);
-
 void
 acpi_tb_print_table_header(acpi_physical_address address,
 			   struct acpi_table_header *header);

drivers/acpi/acpica/evxfevnt.c

@@ -71,7 +71,7 @@ acpi_status acpi_enable(void)
 
 	/* ACPI tables must be present */
 
-	if (!acpi_tb_tables_loaded()) {
+	if (acpi_gbl_fadt_index == ACPI_INVALID_TABLE_INDEX) {
 		return_ACPI_STATUS(AE_NO_ACPI_TABLES);
 	}
 

drivers/acpi/acpica/tbfadt.c

@@ -298,7 +298,7 @@ acpi_tb_select_address(char *register_name, u32 address32, u64 address64)
  *
  * FUNCTION:    acpi_tb_parse_fadt
  *
- * PARAMETERS:  table_index         - Index for the FADT
+ * PARAMETERS:  None
  *
  * RETURN:      None
  *
@@ -307,7 +307,7 @@ acpi_tb_select_address(char *register_name, u32 address32, u64 address64)
  *
  ******************************************************************************/
 
-void acpi_tb_parse_fadt(u32 table_index)
+void acpi_tb_parse_fadt(void)
 {
 	u32 length;
 	struct acpi_table_header *table;
@@ -319,11 +319,11 @@ void acpi_tb_parse_fadt(u32 table_index)
 	 * Get a local copy of the FADT and convert it to a common format
 	 * Map entire FADT, assumed to be smaller than one page.
 	 */
-	length = acpi_gbl_root_table_list.tables[table_index].length;
+	length = acpi_gbl_root_table_list.tables[acpi_gbl_fadt_index].length;
 
 	table =
-	    acpi_os_map_memory(acpi_gbl_root_table_list.tables[table_index].
-			       address, length);
+	    acpi_os_map_memory(acpi_gbl_root_table_list.
+			       tables[acpi_gbl_fadt_index].address, length);
 	if (!table) {
 		return;
 	}

drivers/acpi/acpica/tbutils.c

@@ -97,29 +97,6 @@ acpi_status acpi_tb_initialize_facs(void)
 }
 #endif				/* !ACPI_REDUCED_HARDWARE */
 
-/*******************************************************************************
- *
- * FUNCTION:    acpi_tb_tables_loaded
- *
- * PARAMETERS:  None
- *
- * RETURN:      TRUE if required ACPI tables are loaded
- *
- * DESCRIPTION: Determine if the minimum required ACPI tables are present
- *              (FADT, FACS, DSDT)
- *
- ******************************************************************************/
-
-u8 acpi_tb_tables_loaded(void)
-{
-
-	if (acpi_gbl_root_table_list.current_table_count >= 4) {
-		return (TRUE);
-	}
-
-	return (FALSE);
-}
-
 /*******************************************************************************
  *
  * FUNCTION:    acpi_tb_check_dsdt_header
@@ -392,7 +369,8 @@ acpi_status __init acpi_tb_parse_root_table(acpi_physical_address rsdp_address)
 		    ACPI_COMPARE_NAME(&acpi_gbl_root_table_list.
 				      tables[table_index].signature,
 				      ACPI_SIG_FADT)) {
-			acpi_tb_parse_fadt(table_index);
+			acpi_gbl_fadt_index = table_index;
+			acpi_tb_parse_fadt();
 		}
 
 next_table: