Attention is currently required from: Pranava Y N, Subrata Banik.
Sukumar Ghorai has posted comments on this change by Sukumar Ghorai. ( https://review.coreboot.org/c/coreboot/+/84956?usp=email )
Change subject: mb/google/fatcat: Disable package c-state auto-demotion ......................................................................
Patch Set 1:
(2 comments)
File src/mainboard/google/fatcat/variants/baseboard/fatcat/devicetree.cb:
https://review.coreboot.org/c/coreboot/+/84956/comment/12f69250_73a0f6f2?usp... : PS1, Line 42: demotion
nit: […]
Acknowledged
https://review.coreboot.org/c/coreboot/+/84956/comment/4a9cee3b_ff61992d?usp... : PS1, Line 43: register "disable_package_c_state_demotion" = "true"
initially when this was implemented in ADL, I thought this is a W/A and we won't need this in future […]
Auto demotion is disable for all Chrome platform. MTL ref. a5596a351e633 mb/intel/mtlrvp: Disable package C-state auto demotion. EPB (Dynamic Energy Performance Preference) value comes into playfor C1 demotion heuristics use EPB parameter to balance between power and performance, i.e. low threshold when EPB is low in-order to get C1 demotion faster and vice-versa. Some OS changes the EPB value dynamically in AC/DC mode so in AC gets more demotions and gains performance while in DC it hits less demotion and gains power. Unfortunately, ChromeOS operates at default EPB=0x7 (low EPB) in both AC/DC, so in DC mode it gets much C1 demotion hits than expected (similar to AC mode) and loses power, respectively. Chrome customers decided to disable C1 demotion since they lost power in some KPI when it’s enabled.
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Sukumar Ghorai (Code Review)