What I have to change in u-boot code if I want to change the more DDR size which is supported by DDR controller?

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What I have to change in u-boot code if I want to change the more DDR size which is supported by DDR controller?

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pratikbhatt
Contributor II

Hi,

In QDS board each DDR size is 8GB and there are two DDR so total 16GB DDR is there. Now suppose i want to change that DDR size up to 256GB so each DDR controller can support 128GB for doing that what changed i have to make in u-boot code.

I go through the u-boot code dram_init part from common/board_f.c file but i didn't find any proper field which can describe the DDR size.

When we read the Chip select memory bound register CS0_BNDS  and CS1_BNDS it will shows its value 0x000003ff so what that means? and for change the size of supported DDR i have to changed value in this register?

waiting for your valuable reply.

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lunminliang
NXP Employee
NXP Employee

Hello Pratik Bhatt,

256GB requires 40 bit physical addressing. What is your target device? LS2085A?

CSn_BNDS defines the starting and ending address(This value is compared against the 16 msbs of the 40-bit address) of the memory space that corresponds to the CS. Value 0x000003ff means it maps from 0x0000000000 to 0x03ffffffffff. It equals the size of physical DRAM and need to be changed if the size changes.

Regards

Lunmin

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pratikbhatt
Contributor II

Yes my device is LS2085A.

And yes the value in CSn_BNDS registers is define the the size of the physical DRAM which is connected and we need to change is when the size is changes. But  while referring the u-boot code I came to conclusion, the value 0x3ff which is updating in CSn_BNDS register is calculating from DIMM's SPD parameters . So i am assuming if we changed the DRAM size and put the higher sized DRAM in DIMM ( like 32GB DRAM) the values in CSn_BNDS registers will be updates automatically, so we don't have to change anything in u-boot code. Please let me know lunminliang  my assumption is right or wrong.

Thank you for your valuable answer lunminliang.

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