[XS] Change in coreboot[main]: mb/google/brox: Disable Tccold Handshake

[Ashish Kumar Mishra (Code Review)]

Ashish Kumar Mishra has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/82105?usp=email )

Change subject: mb/google/brox: Disable Tccold Handshake
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mb/google/brox: Disable Tccold Handshake

This patch disables Tccold Handshake to prevent possible display flicker
issue for Brox. Please refer Intel doc#723158 for information.

BUG=None
BRANCH=None
TEST=Boot Brox, verify upd setting.

Change-Id: Ifcc5937bb78d3226100df5db1b9e7737083963a7
Signed-off-by: Ashish Kumar Mishra 
---
M src/mainboard/google/brox/variants/baseboard/brox/devicetree.cb
1 file changed, 4 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/05/82105/1

diff --git a/src/mainboard/google/brox/variants/baseboard/brox/devicetree.cb b/src/mainboard/google/brox/variants/baseboard/brox/devicetree.cb
index f901db9..a4018c2 100644
--- a/src/mainboard/google/brox/variants/baseboard/brox/devicetree.cb
+++ b/src/mainboard/google/brox/variants/baseboard/brox/devicetree.cb
@@ -21,6 +21,10 @@
    # seen on J0 and Q0 SKUs
    register "disable_package_c_state_demotion" = "1"

+	# As per Intel Advisory doc#723158, the change is required to prevent possible
+	# display flickering issue.
+	register "disable_dynamic_tccold_handshake" = "true"
+
    # DPTF enable
    register "dptf_enable" = "1"