Author here. It is correct that mainline U-Boot can handle the i.MX8M DDR PHY, but it is still dependent on these blobs being provided. See here: https://githu

Author here. It is correct that mainline U-Boot can handle the i.MX8M DDR PHY, but it is still dependent on these blobs being provided. See here: https://github.com/u-boot/u-boot/blob/master/arch/arm/mach-imx/imx8m/imximage-8mn-ddr4.cfg#L14 https://github.com/u-boot/u-boot/blob/master/arch/arm/mach-i... I don't know whether RK3399 uses Synopsys. There are other DDR4 PHY IP providers, like Cadence, which don't require firmware.