ACPI: Add support to parse 2nd MADT
When a BIOS bug presents multiple APIC/MADTs,
Linux currently uses the 1st and ignores the 2nd.
But some machines work better if we use the 2nd.
http://bugzilla.kernel.org/show_bug.cgi?id=7465
Add a warning and boot parameter "acpi_apic_instance=2"
to allow parsing the 2nd.
No change to default behaviour in this patch.
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c
index 849e2c3..c341918 100644
--- a/drivers/acpi/tables.c
+++ b/drivers/acpi/tables.c
@@ -42,7 +42,9 @@
static struct acpi_table_desc initial_tables[ACPI_MAX_TABLES] __initdata;
-void acpi_table_print_madt_entry(struct acpi_subtable_header * header)
+static int acpi_apic_instance __initdata;
+
+void acpi_table_print_madt_entry(struct acpi_subtable_header *header)
{
if (!header)
return;
@@ -183,8 +185,10 @@
if (!handler)
return -EINVAL;
- /* Locate the table (if exists). There should only be one. */
- acpi_get_table(id, 0, &table_header);
+ if (strncmp(id, ACPI_SIG_MADT, 4) == 0)
+ acpi_get_table(id, acpi_apic_instance, &table_header);
+ else
+ acpi_get_table(id, 0, &table_header);
if (!table_header) {
printk(KERN_WARNING PREFIX "%4.4s not present\n", id);
@@ -237,10 +241,15 @@
int __init acpi_table_parse(char *id, acpi_table_handler handler)
{
struct acpi_table_header *table = NULL;
+
if (!handler)
return -EINVAL;
- acpi_get_table(id, 0, &table);
+ if (strncmp(id, ACPI_SIG_MADT, 4) == 0)
+ acpi_get_table(id, acpi_apic_instance, &table);
+ else
+ acpi_get_table(id, 0, &table);
+
if (table) {
handler(table);
return 0;
@@ -248,6 +257,31 @@
return 1;
}
+/*
+ * The BIOS is supposed to supply a single APIC/MADT,
+ * but some report two. Provide a knob to use either.
+ * (don't you wish instance 0 and 1 were not the same?)
+ */
+static void __init check_multiple_madt(void)
+{
+ struct acpi_table_header *table = NULL;
+
+ acpi_get_table(ACPI_SIG_MADT, 2, &table);
+ if (table) {
+ printk(KERN_WARNING PREFIX
+ "BIOS bug: multiple APIC/MADT found,"
+ " using %d\n", acpi_apic_instance);
+ printk(KERN_WARNING PREFIX
+ "If \"acpi_apic_instance=%d\" works better, "
+ "notify linux-acpi@vger.kernel.org\n",
+ acpi_apic_instance ? 0 : 2);
+
+ } else
+ acpi_apic_instance = 0;
+
+ return;
+}
+
/*
* acpi_table_init()
*
@@ -257,9 +291,22 @@
* result: sdt_entry[] is initialized
*/
-
int __init acpi_table_init(void)
{
acpi_initialize_tables(initial_tables, ACPI_MAX_TABLES, 0);
+ check_multiple_madt();
return 0;
}
+
+static int __init acpi_parse_apic_instance(char *str)
+{
+
+ acpi_apic_instance = simple_strtoul(str, NULL, 0);
+
+ printk(KERN_NOTICE PREFIX "Shall use APIC/MADT table %d\n",
+ acpi_apic_instance);
+
+ return 0;
+}
+
+early_param("acpi_apic_instance", acpi_parse_apic_instance);