We have designed SoM based on i.MX6 Quad processor (PN; MCIMX6Q6AVT10AD) with 1GB DDR3 ( PN: IS43TR16128B -125KBLI). The DDR3 is routed in T-topology, with 4x DDR3 devices. The board is in production.
Our issue is that 20% of the modules fails to boot during production test. We have to re-try DDR calibration to make these modules passed. I am just wondering , is it normal to do a DDR calibration for each production lot? ( even if I don't change any design or component etc)
Recently we build 1000 modules together. We did a DDR calibration for this batch. But still all module built on this batch doesn't boot well with this DDR calibration setting..
We are using u-boot version: