Re: [PATCH v2 2/4] dt-bindings: memory: Add binding for NVIDIA Tegra30 External Memory Controller

From: Rob Herring
Date: Wed May 01 2019 - 20:17:35 EST

On Wed, May 1, 2019 at 7:06 PM Dmitry Osipenko <digetx@xxxxxxxxx> wrote:
> 30.04.2019 1:05, Rob Herring ÐÐÑÐÑ:
> > On Sun, Apr 14, 2019 at 11:20:07PM +0300, Dmitry Osipenko wrote:
> >> Add device-tree binding for NVIDIA Tegra30 External Memory Controller.
> >> The binding is based on the Tegra124 EMC binding since hardware is
> >> similar, although there are couple significant differences.
> >
> > My comments on Tegra124 binding apply here.
> The common timing definition doesn't fully match the definition that is
> used by Tegra's Memory Controller, thus the DQS (data strobe) timing
> parameter is comprised of multiple sub-parameters that describe how to
> generate the strobe in hardware. There are also more additional
> parameters that are specific to Tegra and they are individually
> characterized for each memory model and clock rate. Hence the common
> timing definition isn't usable.

I don't understand. Every PC in the world can work with any DIMM
(within a given generation) just with SPD data. Why is that not
sufficient here?

In any case, it seems for Tegra124 a different approach is going to be
taken. Seems like an "avoid DT" solution to me, but if it's contained
within the firmware it's not my problem.