Is it possible to initilize DDR with DCD on iMX8MM?

[alexjun]

Hi,

igorpadykov‌

bernhardfink‌

Before answering this question, maybe we should have answer for these 2 questions:

- Can we use the same DDR configuration registers for one type of board? Or we have to train DDR for every board, even they are manufactured with identical components and steps.

- If we can reused DDR configuration to skip training, can we add these value to DCD file for DDR initilization? Or we have to write to register with u-boot SPL like bootloader?

I see there is write data command in DCD section of imx8MM manual, but mkimage tools in u-boot does not support write command. I am not sure whether the write command is just not implemented yet.

Thank you!

Jun

[igorpadykov]

Hi Jun

>Can we use the same DDR configuration registers for one type of board?

yes

>- If we can reused DDR configuration to skip training, can we add these value to

>DCD file for DDR initilization? Or we have to write to register with u-boot SPL like bootloader?

there is no dcd structure in u-boot like i.MX6/7 series, as phy firmware is too large to fit to IRAM

when using dcd structure.

Best regards
igor
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[alexjun]

Hi igor,

I see there is DCD write command in manual section 6.1.6.2.1 of Rev. 1, 03/2019. You said u-boot does not implement DCD in mkimage. I guess it is doable but not necessary so far, right?

If we can use the identical DDR related configuration to one board model, can we skip DDR training firmware and write the DDR phy registers value directly with SPL like boot loader?  Or there is timing sequence operation in firmware and we have to use firmware to initialize DDR?

If firmware is a must to initialize DDR, is the information in manual enough to implement DDR initialization, including registers manipulation and firmware handling? I cannot reference u-boot SPL code because license issue.

Best Regards.

Jun

[igorpadykov · Accepted solution]

Hi Jun

yes ROM supports DCD structure but it is not used for boot.

JEDEC requires data training for LPDDR4 and DDR4 as part of the initialization.
i.MX8M(Mini) DDR PHY contains a micro-controller which executes data training firmware.

>is the information in manual enough to implement DDR initialization, including

>registers manipulation and firmware handling? I

firmware provided by the IP vendor in binary form.

DDR controller requires firmware and DDR must go through training to be usable.
Two firmware files used by the PHY micro-controller: instruction memory image and data memory image.
User simply needs to load it and run it, U-boot provides a framework for this.

Best regards
igor