Skip to content

Commit

Permalink
ACPI: Add support to parse 2nd MADT
Browse files Browse the repository at this point in the history
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>
  • Loading branch information
Len Brown committed Mar 11, 2007
1 parent be52146 commit a1fdcc0
Show file tree
Hide file tree
Showing 2 changed files with 58 additions and 5 deletions.
6 changes: 6 additions & 0 deletions Documentation/kernel-parameters.txt
Original file line number Diff line number Diff line change
Expand Up @@ -138,6 +138,12 @@ and is between 256 and 4096 characters. It is defined in the file

See also Documentation/pm.txt, pci=noacpi

acpi_apic_instance= [ACPI, IOAPIC]
Format: <int>
2: use 2nd APIC table, if available
1,0: use 1st APIC table
default: 0

acpi_sleep= [HW,ACPI] Sleep options
Format: { s3_bios, s3_mode }
See Documentation/power/video.txt
Expand Down
57 changes: 52 additions & 5 deletions drivers/acpi/tables.c
Original file line number Diff line number Diff line change
Expand Up @@ -42,7 +42,9 @@ static char *mps_inti_flags_trigger[] = { "dfl", "edge", "res", "level" };

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;
Expand Down Expand Up @@ -183,8 +185,10 @@ acpi_table_parse_entries(char *id,
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);
Expand Down Expand Up @@ -237,17 +241,47 @@ acpi_table_parse_madt(enum acpi_madt_type id,
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;
} else
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()
*
Expand All @@ -257,9 +291,22 @@ int __init acpi_table_parse(char *id, acpi_table_handler handler)
* 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);

0 comments on commit a1fdcc0

Please sign in to comment.