tree 779bca81d54b8d4e589325e0e94b9e15ff606b58
parent 8ec98507845276119d8a9d5626934dedcb35f2dd
author William wu <wulf@rock-chips.com> 1475133521 +0800
committer chrome-bot <chrome-bot@chromium.org> 1475726319 -0700

gru: Add USB 2.0 PHY tuning for Kevin PHY0 and PHY1

We found that Kevin board PHY0 and PHY1 eye-diagram margin
is not enough to make compliance test pass, and the PHY0 USB
SI is worse than PHY1, because of the higher PCB impedance.

For PHY0, we can't improve the eye-diagram by SW PHY tuning,
so we need to reduce the RBIAS resistance from 133 ohm to 115
ohm, it can help to increase the eye-height.

For PHY1, we can improve the eye-diagram by setting the max
pre-emphasis level.

And after the above change, the USB2 signal amplitude will
become larger at the test point near to SOC USB2 PHY, in order
to avoid mis-trigger the disconnect detection (650mV), we need
to disable pre-emphasize in eop state.

BRANCH=None
BUG=chrome-os-partner:53863
TEST=do USB 2.0 compliance test for Kevin C0 and C1 port.

Change-Id: I00cb325b9938e4276cc77b5d6f5faa7023379608
Signed-off-by: William wu <wulf@rock-chips.com>
Reviewed-on: https://chromium-review.googlesource.com/390615
Commit-Ready: Julius Werner <jwerner@chromium.org>
Tested-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>