[mswann]

After digging through some resources on the web I now believe that this is indeed still true - at least I couldn't find anything to the contrary (apparently you have to provide the firmware blob outside of U-Boot, which then loads it at runtime). This probably means the Rockchip SoCs I was talking about don't use Synopsys IP for the DDR PHY (although they tend to use a lot of Synopsys IP for all kinds of other components).

I wonder how I could have missed that issue with the Librem 5 till now.

[hlandau]

Author here. This is correct. There are other DDR PHY IP providers such as Cadence, which did not elect to require firmware blobs in their design. You could say that the Synopsys DDR4 PHY design is a little overengineered. I've confirmed the presence of these blobs in i.MX8M BSPs myself. See also Purism's blogpost discussing this very subject.