Why imx8mq DRAM Address Start from 0x40000000??

[shangregister]

Hi 

I find the code in uboot include/configs/imx8mq_evk.h

CONFIG_SYS_SDRAM_BASE   0x40000000   //Start from 1GB??

PHY_SDRAM                              0x40000000   //Start from 1GB??

PHY_SDRAM_SIZE                     0xc0000000   //3GB

and Kernel device tree memory map

memory@0x40000000         //Start from 1GB????

{

   device_type= "memory";

   reg=<0x00000000 0x40000000 0 0xc0000000>   //whats the meaning ??<START ADDRSS 64bit ,  SIZE 64bit > from 1GB to 3GB ??

}

hanson

[Yuri]

Hello,

   use 2.1.2 (Cortex-A53 Memory Map) in the Reference Manual.

https://www.nxp.com/webapp/Download?colCode=IMX8MDQLQRM 

Have a great day,

Yuri

-------------------------------------------------------------------------------

Note:

- If this post answers your question, please click the "Mark Correct" button. Thank you!

- We are following threads for 7 weeks after the last post, later replies are ignored

Please open a new thread and refer to the closed one, if you have a related question at a later point in time.

[shangregister]

so can i make the DDR start Address from 0x40000000 to 0x80000000???

[Yuri]

Hello,

  Physical DRAM address area starts from 0x4000_0000.  It is possible to use other

address in software, assuming part of memory is not used.

Regards,

Yuri.

[shangregister]

because i find the DDR Address in data sheet from 0x4000_000 to 1_3FFF_FFFF .

so is it can not modify the start address between 0x4000_0000 to 1_3FFF_FFFF even don't care the Dram size?

e.g 

- START 0x4000_0000

+START 0x4100_0000

[Yuri]

Hello,

  Only 3GBytes address range of DRAM is available in 32-bit address range, used in U-boot.

Regards,

Yuri.