Since this is a portable battery-powered device, rather than first pushing to open-source the DDR training blob, which is non-resident in memory after it's done it's job and a fairly small binary (less chance for hiding bugs), I'd say it's more important to get open-sourced the support in the BL31 Trusted Firmware for dynamic voltage and frequency scaling of DRAM, and support for maximum power savings in suspend mode.
Rockchip have not fully open-sourced the DRAM DVFS support in BL31, but it's key to achieving full run-time battery life on portable devices - see https://xnux.eu/log/083.html
And the system suspend implementation that Rockchip did open-source in upstream BL31 lacks some functionality compared to their binary BL31, mostly about powering off as many peripherals as possible to save power.
I'm not saying don't bother opening the DDR training, just that these two things are much more important for a portable battery-powered device.