[U-Boot] Issues configuring Samsung K4B2G1646Q DDR3 on am3352

[Egli, Samuel]

Hi Tom,
I observed some issues on our Siemens CPU boards with am3352 configuring 2Gbit DDR3 from Samsung (K4B2G1646Q). Before we used a 1 Gbit DDR3 memory from Samsung as well and other manufacturers that worked fine. With 2 Gbit I noticed, after some trial and error (and adapting tRFC parameters to the new size), that for Samsung I need to wait some extra time (around 200us) after calling the configuration function config_ddr(...) before proceeding.

This is necessary when a soft reset happens but not when the device makes a power cycle. And this is only an issue for Samsung K4B2G1646Q. We also have some hardware with 2Gbit DDR3 from ISSI that don't see this issue. From a datasheet perspective there shouldn't be any significant differences but of course I cannot vouch for it. 

So my question is now if you know somebody that observed similar issues with K4B2G1646Q DDR3 and if there is a better solution than adding a udelay(200) after the configuration call? I don't understand the issue completely, so I guess there might be a better solution out there.

Kind regards
 Sam

Siemens Schweiz AG, Building Technologies Division, International Headquarters
Infrastructure & Cities Sector
Building Technologies Division
Control Products & Systems
IC BT CPS R&D ZG FW CCP
Gubelstrasse 22
6300 Zug, Schweiz
Tel: +41 41 724-3024
mailto:samuel.egli at siemens.com