How can I change the LPDDR4x configuration on U-boot

[Byungkook Kim]

Dear Geniuses, 
 
I'm a beginner in the embedded world, so naturally I have a few questions. ^^;;
I will ask the most curious thing among them.
It is a very difficult problem for me, but I think it is a simple for you.
Please teach me.

I bought SBC(Single Board Computer) to study embedded Linux & U-boot recently.
  - Processor : Amlogic A311D2
  - RAM : 8GB LPDDR4X

 
2pcs 4GB LPDDR4x DRAM has mounted on the SBC so total density is 8GB.
The 4GB LPDDR4X DRAM structure used for this SBC is like as below.
 
  
The SBC working well with U-boot & Ubuntu. 
 
### My Question ###
I have 2GB LPDDR4x devices and the structure is like as below.
 
 
The structural difference is the 4GB device is 2-rank(2CS) structure and the 2GB device is 1-rank(1CS) structure. 
If I replace the LPDDR4X device from 2pcs 4GB to 2pcs 2GB then I think it needed to modify the u-boot codes.
I found 'timing.c' file and change the DDR_SIZE_TYPE define like as below.
- Before : #define DDR_SIZE_TYPE_1 AN_408_DDR0_4G_DDR1_4G_RANK01
- After   : #define DDR_SIZE_TYPE_1 AN_408_DDR0_2G_DDR1_2G
 
 
 
But I don't know the exact modify points, it seems that this alone is nor enough. 
Please teach me. 
 
Best Regards,
BK Kim