Custom imx8mm DDR3

[houssem_chaaban]

Hello

We know that iMX8MM boards use low power DDR4 and getting 1.1V from PMIC while running up the board,

But we made our custom board based on the same iMX8MM architecture but we chose to use DDR3 instead, and for that reason the tension for the BUCK8 register of the Cortex-m4 need to get 1.35V as showing this table:

In order to achieve that, we made these steps:

1.  Connect JLINK EDU version10.1 with the iMX8MM JTAG pins
2. Use IAR embedded software with iMX8mm patch to connect with the Cortex-m4
3. Connection is successfully achieved

Now when we make simple LED blinking test example it works fine, but after rebooting the board the program is gone,

so it's programmed in the RAM and we don't know where/how to make it permanent,

we did check that the Cortex-m4 of IMX8MM has no flash size.

So the question is: where and how to change the BUCK8 register and make that permanent so our DDR3 RAM be loaded in order to boot the eMMC/sdcard Linux image.

Best regards,
Houssem

[Yuri]

Hello,

    The boot procedure of the i.MX8M includes loading  HDMI and DDR controller’s  firmware, 

that must be loaded prior to executing the bootloader. Then - ATF should be run, and after that 

U-boot starts. So, in U-boot , under A53 core, PMIC configuration may be  implemented.   
  Use section 3.2.3 (Adding new driver initialization code to board files) of Chapter 3  (Porting

U-Boot) of “i.MX_Porting_Guide.pdf”.

Have a great day,

Yuri

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