Patch merged into coreboot/master: google/gru: Tuning USB 2.0 PHY0 and PHY1 squelch detection threshold

the following patch was just integrated into master:
commit ebbdd2882e49c6f94a573ebcf11d04ae1129a928
Author: William wu 
Date:   Mon Jan 23 20:54:22 2017 +0800

google/gru: Tuning USB 2.0 PHY0 and PHY1 squelch detection threshold

According to USB 2.0 Spec Table 7-7, the High-speed squelch
    detection threshold Min 100mV and Max 150mV, and we set USB
    2.0 PHY0 and PHY1 squelch detection threshold to 150mV by
    default, so if the amplitude of differential voltage envelope
    is < 150 mV, the USB 2.0 PHYs envelope detector will indicate
    it as squelch.

On Kevin board, if we connect usb device with Samsung U2 cable,
    we can see that the impedance of U2 cable is too big according
    to the eye-diagram test report, and this cause serious signal
    attenuation at the end of receiver, the amplitude of differential
    voltage falls below 150mV.

This patch aims to reduce the PHY0 and PHY1 otg-ports squelch
    detection threshold to 125mV (host-ports still use 150mV by
    default), this is helpful to increase USB 2.0 PHY compatibility.

BRANCH=gru
    BUG=chrome-os-partner:62320
    TEST=Plug Samsung U2 cable + SEC P3 HDD 500GB/Galaxy S3 into
    Type-C port, check if the USB device can be detected.

Change-Id: Ia0a2d354781c2ac757938409490f7c4eecdffe61
    Signed-off-by: Patrick Georgi 
    Original-Commit-Id: 7d74311c25762668386061234df0562f84b7203e
    Original-Change-Id: Ib20772f8fc2484d34c69f5938818aaa81ded7ed8
    Original-Signed-off-by: William wu 
    Original-Reviewed-on: https://chromium-review.googlesource.com/431015
    Original-Commit-Ready: Caesar Wang 
    Original-Tested-by: Inno Park 
    Original-Reviewed-by: Julius Werner 
    Reviewed-on: https://review.coreboot.org/18462
    Reviewed-by: Martin Roth 
    Tested-by: build bot (Jenkins)

See https://review.coreboot.org/18462 for details.

-gerrit