tree fd15ae3b6fc03a16d269a67c2f28833e9207494b
parent 9a6ce2a8ee9b8579409cc3b6da7ee7709dc8bf8e
author Faiz Abbas <faiz_abbas@ti.com> 1548851922 +0530
committer Tom Rini <trini@konsulko.com> 1549716658 -0500

mmc: omap_hsmmc: Workaround errata regarding SDR104/HS200 tuning failures (i929)

Errata i929 in certain OMAP5/DRA7XX/AM57XX silicon revisions
(SPRZ426D - November 2014 - Revised February 2018 [1]) mentions
unexpected tuning pattern errors. A small failure band may be present
in the tuning range which may be missed by the current algorithm.
Furthermore, the failure bands vary with temperature leading to
different optimum tuning values for different temperatures.

As suggested in the related Application Report (SPRACA9B - October 2017
- Revised July 2018 [2]), tuning should be done in two stages.
In stage 1, assign the optimum ratio in the maximum pass window for the
current temperature. In stage 2, if the chosen value is close to the
small failure band, move away from it in the appropriate direction.

References:
[1] http://www.ti.com/lit/pdf/sprz426
[2] http://www.ti.com/lit/pdf/SPRACA9

Signed-off-by: Faiz Abbas <faiz_abbas@ti.com>