i.mx6 memory dcd table only reporting 1/2 of memory in uboot/linux

[dennis3]

This is a continuation of a couple other discussions:

1) Original problem booting custom board w/ dcd parameters.

i.mx6d pop dcd generation -> solution use updated script aid v1.3

Our memory configuration as input into the new script aid.

Device Information
Memory type:	LPDDR2
Manufacturer:	Micron - POP Package
Memory part number:	EDB8164B4PT-1DAT-F-D
Density per chip select (Gb):	4
Number of Chip Selects per channel used2	1
Number of Channels used2	2
DRAM density per channel (Gb)	4
Total DRAM density (Gb)	8
Number of ROW Addresses2	14
Number of COLUMN Addresses2	10
Number of BANKS2	8
Bus Width (input 16, 32, or 64 bits)2	32
Clock Cycle Freq (MHz)3	400
Clock Cycle Time (ns)	2.5

4Gb per channel X 2 Channels = 8Gb total. (1GiB)

This boots successfully in uboot/linux but the total ram reported available to the operating system is 512MiB instead of 1GiB.

I'm considering that maybe I misunderstood the data sheet and mixed up number of channels/chip selects or density but other combinations don't boot the device at all.

Any suggestions of where to look.  I don't know if this is a script aid error or a mis-configuration or if there is an additional step we need to be taking after boot to make available all memory.

Note: the ddr stress test tool can see 1GiB of memory and calibrate it.

[igorpadykov · Accepted solution]

Hi Dennis

one can check uboot parameter  #define PHYS_SDRAM_SIZE 

mx6dqscm.h\configs\include - uboot-imx - i.MX U-Boot 

Best regards
igor
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[dennis3]

OK, thanks for the tip in the right direction. We use a little bit newer version of u-boot than the referenced file, but that helped me start looking in the right direction for where the calculation was coming from.  I found that the dram size was being calculated based on ddr settings but our board has lpddr2.  The channel count was not being taken into consideration.  (Our board is based on the imx6sabresd board which has ddr).  So the registers were indeed right, but uboot was simply failing to add the total memory bits correctly.