drivers/pc80/tpm: Update default acpi path

The existing default path of PCI0.LPCB is missing the \_SB prefix and prevents Linux from detecting the TPM.
This is assuming that normally the LPCB device is most commonly on \_SB.PCI0.LPCB.

SSDT excerpt without the patch:
"""
DefinitionBlock ("", "SSDT", 2, "CORE  ", "COREBOOT", 0x0000002A)
{
    External (_SB_.PCI0.GFX0, DeviceObj)
[...]
    External (_SB_.PCI0.SATA, DeviceObj)
    External (PCI0.LPCB, DeviceObj)
[...]
    Scope (PCI0.LPCB)
    {
        Device (TPM)
[...]
    Scope (\_SB.PCI0.GFX0)
    {
        Method (_DOD, 0, NotSerialized)  // _DOD: Display Output Devices
[...]
"""

SSDT excerpt with the patch:
"""
DefinitionBlock ("", "SSDT", 2, "CORE  ", "COREBOOT", 0x0000002A)
{
    External (_SB_.PCI0.GFX0, DeviceObj)
[...]
    External (_SB_.PCI0.LPCB, DeviceObj)
[...]
    External (_SB_.PCI0.SATA, DeviceObj)
[...]
    Scope (\_SB.PCI0.LPCB)
    {
        Device (TPM)
[...]
    Scope (\_SB.PCI0.GFX0)
    {
        Method (_DOD, 0, NotSerialized)  // _DOD: Display Output Devices
[...]
"""

After the patch the TPM shows up in /sys/bus/acpi/devices/PNP0C31:00.
Previously it was missing and not detected by the kernel.

Change-Id: I615b4873ca829a859211403c84234d43d60f2243
Signed-off-by: Tobias Diedrich <ranma+coreboot@tdiedrich.de>
Reviewed-on: https://review.coreboot.org/18315
Tested-by: build bot (Jenkins)
Reviewed-by: Nicola Corna <nicola@corna.info>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/drivers/pc80/tpm/tpm.c b/src/drivers/pc80/tpm/tpm.c
index 83dc92348f..3c3e491aa3 100644
--- a/src/drivers/pc80/tpm/tpm.c
+++ b/src/drivers/pc80/tpm/tpm.c
@@ -876,7 +876,7 @@ static void lpc_tpm_fill_ssdt(struct device *dev)
 					CONFIG_TPM_TIS_BASE_ADDRESS, 0x5000);
 
 	if (!path) {
-		path = "PCI0.LPCB";
+		path = "\\_SB_.PCI0.LPCB";
 		printk(BIOS_DEBUG, "Using default TPM ACPI path: '%s'\n", path);
 	}