AM335x DDR size in Linux

sachin sagar

Hi,

I am working in DDR section, we are changing the DDR size to 1GB , where do i need to change the size of DDR at uboot level so that kernel has to know only this much DDR is available. I tried to change in DTSI

memory {
device_type = "memory";
reg = <0x80000000 0x8000000>; /* 256 MB */
};

but it is not affecting any where, please suggest me where the actual location to change..?

over 8 years ago

0 Yordan Kovachev over 8 years ago

TI__Guru**** 161600 points

Hi,

In u-boot code DDR settings are done in:
arch/arm/cpu/armv7/am33xx/ddr.c
arch/arm/cpu/armv7/am33xx/emif4.c

Note that, when you set ddr timings correctly, u-boot code automatically detects & calculate the size of the DDR.

Further help on setting emif register & ddr timings can be found on the following wiki:
processors.wiki.ti.com/.../AM335x_EMIF_Configuration_tips

Hope this helps.

Best Regards,
Yordan

0 sachin sagar over 8 years ago in reply to Yordan Kovachev

Intellectual 670 points

Hi,

I am having doubt that , can't we minimize the DDR size by defining it in u-boot or kernel, if not why ? if yes where we can? please suggest..

0 Yordan Kovachev over 8 years ago in reply to sachin sagar

TI__Guru**** 161600 points

Board, definitions are done in am335x_evm.h, ti_am335x_common.h & ti_armv7_common.h. If you check these files, you'll see that you have only the start (base address) of the ram & the max size. There is no definition of the ram size.
After that if you check emif4.c, you'll see that the above two definitions are used in:
gd->ram_size = get_ram_size(
(void *)CONFIG_SYS_SDRAM_BASE,
CONFIG_MAX_RAM_BANK_SIZE);
the get_ram_size() function is located in: common/memsize.c.

Best Regards,
Yordan

0 sachin sagar over 8 years ago in reply to Yordan Kovachev

Intellectual 670 points

Thanks for the replay,

Do we need to change the driver for DDR3 if we change the chip, previously it was MT41K256M16HA-125: E and now we are using MT41K512M16HA-125 IT:A , does it needs any change?, please suggest.

0 sachin sagar over 8 years ago in reply to sachin sagar

Intellectual 670 points

Hi,

Please replay me for the above doubt, does it needs only timing parameters changes or driver need to change...? As i am new to this, if i am asking wrong please tell and show me the correct way.

0 sachin sagar over 8 years ago in reply to sachin sagar

Intellectual 670 points

Hi,

can anyone please replay to my above question , as i am new to DDR section if i am asking wrong please let me know.

0 Biser Gatchev-XID over 8 years ago in reply to sachin sagar

TI__Guru**** 393215 points

You need to check your SDRAM_TIM_1, SDRAM_TIM_2, and SDRAM_TIM_3 register settings and the SDRAM_CONFIG register settings against the new DDR datasheet.

0 sachin sagar over 8 years ago in reply to Biser Gatchev-XID

Intellectual 670 points

Thank you for the replay,

My doubt is , I can see there is a ddr folder in uboot/driver folder, is that ddr driver is really necessary or only timing parameters changes is enough.. ? please suggest.

0 Biser Gatchev-XID over 8 years ago in reply to sachin sagar

TI__Guru**** 393215 points

What I posted in my previous post is enough. There is no such thing as a DDR driver in Linux.

0 sachin sagar over 8 years ago in reply to Biser Gatchev-XID

Intellectual 670 points

Thank you so much.

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AM335x DDR size in Linux