[S] Change in coreboot[main]: mb/asrock/z77_extreme4: Implement voltage settings

[Riku Viitanen (Code Review)]

Hello build bot (Jenkins),

I'd like you to reexamine a change. Please visit

https://review.coreboot.org/c/coreboot/+/85795?usp=email

to look at the new patch set (#6).

The following approvals got outdated and were removed:
Verified+1 by build bot (Jenkins)

Change subject: mb/asrock/z77_extreme4: Implement voltage settings
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mb/asrock/z77_extreme4: Implement voltage settings

This board has two Nuvoton NCT3933U current DAC chips on SMBus,
enabling firmware to adjust several voltage rails. The correct
registers and constants were reverse engineered by adjusting voltages
in vendor firmware and observing what it wrote. DRAM, PCH, VTT, and
CPU PLL voltages are fully documented in devicetree. Of VREFDQ and
VREFCA, only register addresses are known based on the boardview.

DRAM voltage is automatically adjustable by raminit.

TEST=With few XMP and non-XMP modules. Monitored DRAM voltage on
test point VT10 (located near the SLI logo) with a multimeter.

DIMMs tested (matching and also in weird groupings):
- Corsair CMY16GX3M2A2400C
- G.Skill F3-1600C9-8GAR
- Hynix HMT41GU7BFR8C-RD
- Kingston 9905403-440.A00L
- Kingston KHX1600C10D3/8G
- Micron 4JTF12864AZ-1G4D
- Samsung M378B5173DB0-CK0

Change-Id: Ic59c0c74f070c7d8ebd8e9c1760fe0b491c06a51
Signed-off-by: Riku Viitanen 
---
M src/mainboard/asrock/z77_extreme4/Kconfig
M src/mainboard/asrock/z77_extreme4/devicetree.cb
2 files changed, 25 insertions(+), 0 deletions(-)

git pull ssh://review.coreboot.org:29418/coreboot refs/changes/95/85795/6