According to JEDEC Spec, there is no need to do tuning under HS400 mode
since the Rx signal is aligned with the DS signal. However, MediaTeks
IC need set its "DS delay" internally to ensure it can latch Rx signal
correctly.
In previous version, We provide an "hs400-ds-delay" in device tree to
cover different chipset/PCB design, and it works fine in most cases.
But, with the development of process technology and the big VCore
voltage scale range(may have 0.7V/0.6V/0.55V), it is difficult to find
a suitable "hs400-ds-delay" to cover all of IC corner
cases(SSSS/TTTT/FFFF).
So that We must have the ability to do hs400 online tuning.
MTK-Commit-Id: 1ab18425204b67a0a602ff9cd736f1aa748afbca
CR-Id: ALPS07092600
Feature: eMMC
Signed-off-by: lin.gui <lin.gui@mediatek.com>
Change-Id: I0fe5f5da3dfdab7b0ed18485d26cba97ec0ea451
(cherry picked from commit d87f4356682623756f51aadabf76708a9f6df48f)
f4e92540b9