[XS] Change in coreboot[main]: mb/intel/mtlrvp: Disable package C-state auto demotion for rex & ovis

[Sukumar Ghorai (Code Review)]

Sukumar Ghorai has uploaded this change for review. ( https://review.coreboot.org/c/coreboot/+/78278?usp=email )

Change subject: mb/intel/mtlrvp: Disable package C-state auto demotion for rex & ovis
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mb/intel/mtlrvp: Disable package C-state auto demotion for rex & ovis

Package C-state auto demotion feature allows hardware to determine lower
C-state as per platform policy. Since platform sets performance policy
to balanced from hardware, auto demotion can be disabled without
performance impact.

Also, disabling this feature results soc to enter below PC8 state and
additional power savings ~30mW in Local-Video-Playback scenario.

Change-Id: I6ff408280178a24686180f72f79522d2741607a1
Signed-off-by: Sukumar Ghorai 
---
M src/mainboard/intel/mtlrvp/variants/baseboard/mtlrvp_p/devicetree.cb
1 file changed, 3 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/78/78278/1

diff --git a/src/mainboard/intel/mtlrvp/variants/baseboard/mtlrvp_p/devicetree.cb b/src/mainboard/intel/mtlrvp/variants/baseboard/mtlrvp_p/devicetree.cb
index 17a92a8..a0f27f0 100644
--- a/src/mainboard/intel/mtlrvp/variants/baseboard/mtlrvp_p/devicetree.cb
+++ b/src/mainboard/intel/mtlrvp/variants/baseboard/mtlrvp_p/devicetree.cb
@@ -55,6 +55,9 @@
    # Disable C1 C-state auto-demotion
    register "disable_c1_state_auto_demotion" = "1"

+	# Disable PKGC-state demotion
+	register "disable_package_c_state_demotion" = "1"
+
    # Enable energy reporting
    register "pch_pm_energy_report_enable" = "1"