BSP Beginner: i.MX 8M Mini Device Tree & DRAM Questions

cmw — Sun, 27 Jul 2025 02:45:28 GMT

Hello,

I am currently studying the i.MX 8M Mini Reference Manual (IMX8MMRM.pdf, Rev. 3, 11/2020) and the NXP BSP, and I have some questions as a BSP beginner.

Q1.
There are some device nodes described in the Reference Manual but not present in the following Device Tree file:
https://github.com/nxp-imx/linux-imx/blob/lf-6.12.y/arch/arm64/boot/dts/freescale/imx8mm.dtsi
Is this because the imx8mm.dtsi file is written specifically for the EVK?
However, there is also an imx8mm-evk.dtsi file in the same directory.
Why are not all nodes defined as listed in Chapter 2 (Memory Map) of the Reference Manual?
For example, the spdif2 node is mentioned in the RM but is not present in the dtsi.

Q2.
The Reference Manual states that only UART1, UART2, and UART3 support SDMA.
However, I found that the uart4 node in imx8mm.dtsi contains properties like dmas and dma-names.
Does this mean that UART4 can actually use DMA?

Q3.
This question is a bit challenging for me as a beginner, so I hope I can describe it properly.

I have two custom boards based on the i.MX 8M Mini.

One board uses the same DRAM as the i.MX8MM EVK (LPDDR4, 2 GB, MT53D512M32D2DS‑053 WT:D) and works without any issues.
The other board uses a different DRAM (Samsung LPDDR4, 4 GB, likely K4FBE3D4HMMGCJ).

The second board always detects only 2 GB of memory instead of 4 GB.

What I have tried so far:

Makefile
ifdef CONFIG_IMX8M_4G_LPDDR4
obj-y += lpddr4_timing_4g.o
Kconfig
config IMX8M_4G_LPDDR4
bool "Use LPDDR4 4GB DRAM"
xxxx_defconfig
CONFIG_IMX8M_4G_LPDDR4=y
Updated the memory node ranges in both the bootloader DT and kernel DT.

Despite these changes, the system still detects only 2 GB.

My questions:

Do I need to generate a new lpddr4_pmu_train_*.bin file using the i.MX 8M Family DDR Tool for this Samsung LPDDR4 4 GB memory?
Should I also regenerate the lpddr4_timing_4g.c specifically for this DRAM?
Are there any reference documents or application notes available for this process?

I apologize for the long post, but I wanted to provide as many details as possible to avoid repeated clarification.
Thank you very much for your time and support.

Re: BSP Beginner: i.MX 8M Mini Device Tree & DRAM Questions

Rita_Wang — Tue, 29 Jul 2025 08:28:27 GMT

Hi @cmw ,

Q1&A:The imx8mm.dtsi is for the i.MX8MM chip, and imx8mm-evk.dtsi is for NXP i.MX8MM EVK board.

Q2&A: I think you can try, but do not recommend you to do that. Please following our RM.

Q3&A:Yes, for the 4GB LPDDR4 you using, you need to run the DDR tool to generate the proper configration for the new LPDDR4.

I see your setting:

You also need to add the :

git a/include/configs/imx8mm_evk.h b/include/configs/imx8mm_evk.h

index d01ce0c6a0..198d911a76 100644

--- a/include/configs/imx8mm_evk.h

+++ b/include/configs/imx8mm_evk.h

@@ -213,6 +213,14 @@

#define PHYS_SDRAM 0x40000000

#define PHYS_SDRAM_SIZE 0x80000000 /* 2GB DDR */

+#ifdef CONFIG_IMX8M_4G_LPDDR4

+#undef PHYS_SDRAM_SIZE

+#define PHYS_SDRAM_SIZE 0xC0000000 /* 3GB */

+#define PHYS_SDRAM_2 0x100000000

+#define PHYS_SDRAM_2_SIZE 0x40000000 /* 1GB */

+#endif

#define CONFIG_SYS_MEMTEST_START PHYS_SDRAM

#define CONFIG_SYS_MEMTEST_END (CONFIG_SYS_MEMTEST_START + (PHYS_SDRAM_SIZE >> 1))

For ddr tool:

i.MX8MMini (m845S) DDR Register Programming Aid (RPA) - NXP Community

i.MX 8M Family DDR Tool Release - NXP Community

Hope this can do help for you

Wish you have a nice day

Best Regards

Rita

topic Re: BSP Beginner: i.MX 8M Mini Device Tree & DRAM Questions in i.MX Processors

BSP Beginner: i.MX 8M Mini Device Tree & DRAM Questions

What I have tried so far:

My questions:

Re: BSP Beginner: i.MX 8M Mini Device Tree & DRAM Questions