iMX8M mini + 2GB DDR4 boot problems

giacomobiancala — Fri, 03 Jul 2020 13:11:36 GMT

Dear all,

I have some booting problems on my custom board based on iMX8M mini processor.

We use PMIC PCA9450.

Processor code MIMX8MM5DVTLZAA

DDR4 DRAM code (2GB total): 2 x MT40A512M16LY-075:E

DRAM Schematics connections is the same than EVK SCH-35104_B1 (8MMINID4-CPU).

We set main voltage as follows:

- VDD_DRAM&PU = 0,9V

- VDD_DRAM_1V2 = 1,2V

We produced 14 prototipes of this board. 10 boards always boot properly and they have no problems.

The other 4 boards do not boot properly every time. Console output is following:

U-Boot SPL 2018.03-g5f7f913-dirty (Jul 03 2020 - 13:57:13 +0200)
DRAM PHY training for 2400MTS
check ddr4_pmu_train_imem code
check ddr4_pmu_train_imem code pass
check ddr4_pmu_train_dmem code
check ddr4_pmu_train_dmem code pass
Training PASS
DRAM PHY training for 400MTS
check ddr4_pmu_train_imem code
check ddr4_pmu_train_imem code pass
check ddr4_pmu_train_dmem code
check ddr4_pmu_train_dmem code pass
Training PASS
DRAM PHY training for 100MTS
check ddr4_pmu_train_imem code
check ddr4_pmu_train_imem code pass
check ddr4_pmu_train_dmem code
check ddr4_pmu_train_dmem code pass
Training FAILED
DRAM PHY training for 2400MTS
check ddr4_pmu_train_imem code
check ddr4_pmu_train_imem code pass
check ddr4_pmu_train_dmem code
check ddr4_pmu_train_dmem code pass
Training FAILED

There are 2 FAILED on DRAM test so the boot process stops.

If I run RAM Stress Test "mscale_ddr_tool_v310_setup.exe" (both calibration and Stress Test) all works fine so it seems that DDR4 connections have no problems but when I use the UBOOT the booting stops after RAM tests in SPL (only on this 4 boards).

Could you help me?

Thanks

Giacomo

Re: iMX8M mini + 2GB DDR4 boot problems

igorpadykov — Fri, 03 Jul 2020 23:22:41 GMT

Hi Giacomo

if only some boards do not boot properly, this may be poor soldering issue,

one can try to test boards with x-ray screening.

Alternatively one can try to tweak drive strength and ODT parameters using

RPA tool on i.MX 8M Family DDR Tool Release
Check power supply noise or spikes – refering to HW Developers Guide

i.MX 8M Mini Hardware Developer’s Guide

Best regards
igor
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iMX8M mini + 2GB DDR4 boot problems

Re: iMX8M mini + 2GB DDR4 boot problems