IMX 53 change RAM size. U-boot or/and Linux .

[janiscoders]

Hi, we have a custom board based on imx53 QSB, but we have 4*128 MB of RAM (512MB) unlike QSB which has 4*256 MB (1GB).

Everything was working fine until one day we noticed that on large data copying or when RAM is used a lot, then our board (Linux) just hangs and everything stops without any feedback.

I didn't change anything in RAM configuration, because everything was fine. If I make a load on RAM and watch the free memory using free command, then I see that everything hangs around 256MB of memory usage.

I've tried passing the mem=512M value from u-boot, but still the hanging issue. If I pass around 240M, then everything is fine.

So the questions are - could this be a RAM issue? Maybe this is the CS (Chip Select) register issue, because it thinks it has 512Mb. Does everything is reinitialized in Linux from zero? OR memory is initialized in u-boot and fixing there will fix Linux too? Because u-boot is working fine and I don't want to spend time messing there and have no results in Linux.

Could you point me to files in source code where those values can be modified?

Thank you. 

[fabio_estevam · Accepted solution]

The memory initialization is done in the bootloader and the kernel just uses whatever the bootloder has configured.

In U-boot, you can look at the memory initializations at (using mx53 qsb as example here):

uboot-imx.git - Freescale i.MX u-boot Tree

And the RAM size is also passed in the board config file:

http://git.freescale.com/git/cgit.cgi/imx/uboot-imx.git/tree/include/configs/mx53_loco.h?h=imx_v2009...

Search for PHYS_SDRAM_1.

Regards,

Fabio Estevam

[kubiznak_petr]

Hi Fabio,

I'm currently meeting the same problem on Vybrid. Our custom board uses 256 MB DDR3 (128 MB x 16), compared to Tower which uses 128 MB ddr. So I changed the value of PHYS_SDRAM_1_SIZE from (128 * 1024 * 1024) to (256 * 1024 * 1024) in both vybrid.h and vybrid_iram.h in include/configs/. Nothing changed though, still printing "DRAM:  128 MiB" in the U-Boot start sequence.

In board/freescale/vybrid/vybrid.c I noticed that function dram_init() sets a variable gd->ram_size to the value computed in ddr_ctrl_init(). Using md command, I displayed values of the registers used to compute the value (registers DDR_CR001, DDR_CR073, DDR_CR078) and calculated it manually, getting value 0x00200000, which does not make sense.

Don't you please see where the problem could be? Should I somewhere set the 16 bit word length instead of changing PHYS_SDRAM_1_SIZE?

Thank you, Petr

[fabio_estevam]

Hi Petr,

I am not familiar with the Vybrid DDR controller.

I would suggest you to start a new thread so that someone knowledgeable on this line could assist.

Regards,

Fabio Estevam

[janiscoders]

Thank you really much. It seems like that fixed the problem. Simply changed to

#define PHYS_SDRAM_1

CSD0_BASE_ADDR

#define PHYS_SDRAM_1_SIZE    (256 * 1024 * 1024)

#define PHYS_SDRAM_2

CSD1_BASE_ADDR

#define PHYS_SDRAM_2_SIZE    (256 * 1024 * 1024)

in mx53_loco.h without modifying flash_header.S !

And lesson learned - memory initialization is performed only in u-boot.