[coreboot-gerrit] Change in coreboot[master]: nb/intel/x4x/raminit: Rework receive enable calibration

[Arthur Heymans (Code Review)]

Arthur Heymans has posted comments on this change. ( https://review.coreboot.org/18692 )

Change subject: nb/intel/x4x/raminit: Rework receive enable calibration
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Patch Set 16:

Strobe is unreliable :( found DQS high on coarse=5, medium=2. Then when decreasing medium and looking for DQS high while increasing TAP it find it at coarse=5, medium=1, tap=0...
after that it decreases tap so coarse=5, medium=0, tap=14. DQS high is not found later when increasing medium.

Difference with previous code is that tap did not get decreased this way if it was 0.

now it hits the "Not at DQS HIGH d'oh"

a few things could be done:
* check for strobe consistency by running it multiple times
* add a check if (tap == 0) to bring back old behavior
* when finding preamble increase medium until DQS high instead of one medium

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Gerrit-MessageType: comment
Gerrit-Change-Id: I0c970455e609d3ce96a262cbf110336a2079da4d
Gerrit-PatchSet: 16
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