tree 16ef6c2d7e06aa71279bb7b816d645cacadd694d
parent 6b324d99192d543fb29e00bb40935893c85b24a8
author Sukumar Ghorai <sukumar.ghorai@intel.com> 1690799084 -0700
committer Felix Held <felix-coreboot@felixheld.de> 1691158131 +0000

mb/google/{rex,ovis}: Disable C1-state auto demotion for rex & ovis

C1-state auto demotion feature allows hardware to determine C1-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 PC2 and lower
state in camera preview case and save platform power.

Note: C1 demotion heuristics used 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. ChromeOS operates at default EPB=0x7
(low EPB) in both AC/DC, so in DC mode it gets more C1 demotion hits
than expected (similar to AC mode) and losing power respectively.

BUG=b:286328295
TEST=Code compiles and correct value of c1-state auto demotion is
passed to FSP. Also verified PC residency improvement ~10% in
camera preview case.

Change-Id: I548e0e5340dec537d05718dd2f4652e10fb36ac0
Signed-off-by: Sukumar Ghorai <sukumar.ghorai@intel.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/76827
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Subrata Banik <subratabanik@google.com>
Reviewed-by: Sumeet R Pawnikar <sumeet.r.pawnikar@intel.com>
Reviewed-by: Sridhar Siricilla <sridhar.siricilla@intel.com>
Reviewed-by: Kapil Porwal <kapilporwal@google.com>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>