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

[cmw]

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.

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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.

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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?

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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:

1. Makefile

   ifdef CONFIG_IMX8M_4G_LPDDR4

   obj-y += lpddr4_timing_4g.o

2. Kconfig

   config IMX8M_4G_LPDDR4

   bool "Use LPDDR4 4GB DRAM"

3. xxxx_defconfig

   CONFIG_IMX8M_4G_LPDDR4=y

4. 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?

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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.

[Rita_Wang · Accepted solution]

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