limit the linux partition in DDR3 memory of DE1-SOC board

You can limit the memory reserved for linux by specifying the "mem" parameter when booting the linux kernel eg.

bootargs root=/dev/mmcblk0p2 rw rootwait console=ttyS0,115200 mem=800M 

Documented here https://www.kernel.org/doc/html/v4.14/admin-guide/kernel-parameters.html (https://www.kernel.org/doc/html/v4.14/admin-guide/kernel-parameters.html) (Search for "mem=")

Hii Tototo

Using the cable ethernet not the uart can i use this command ?

this command limit the linux to use just 800M of the DDR3 memory?

so to which adress i can write to ddr3 memory from the FPGA ?

--- Quote Start ---

Using the cable ethernet not the uart can i use this command ?

--- Quote End ---

You can set these parameters from within uBoot, independently from your connection.

If you type "printenv" within uBoot you will see the entire environment variables. Probably you can spot some variables that are used for booting the kernel eg. name of the kernel image, boot parameters....

--- Quote Start ---

this command limit the linux to use just 800M of the DDR3 memory?

so to which adress i can write to ddr3 memory from the FPGA?

--- Quote End ---

You can verify this by typing

cat /proc/iomem

It should say something like "00000000-31ffffff : System RAM" and that is the memory range used by kernel. You can do with the rest whatever you want.

Hii Tototo ,

when I type this command "cat /proc/iomem" it gives me

root@socfpga:~# cat /proc/iomem

00000000-31ffffff : System RAM

00008000-006ed827 : Kernel code

00744000-007c355b : Kernel data

ff702000-ff703fff : /soc/ethernet@ff702000

ff704000-ff704fff : /soc/dwmmc0@ff704000

ff705000-ff705fff : ff705000.spi

ffa00000-ffa00fff : ff705000.spi

ffb40000-ffb4fffe : /soc/usb@ffb40000

ffc00000-ffc00fff : c_can_platform

ffc02000-ffc0201f : serial

ffc04000-ffc04fff : /soc/i2c@ffc04000

ffc05000-ffc05fff : /soc/i2c@ffc05000

ffd02000-ffd02fff : /soc/wd@ffd02000

ffe01000-ffe01fff : /soc/amba/pdma@ffe01000

fff01000-fff01fff : fff01000.spi

ffff0000-ffffffff : /soc/sram@ffff0000

means that i can do with the 0x32000000-0x40000000 whatever i want

--- Quote Start ---

means that i can do with the 0x32000000-0x40000000 whatever i want

--- Quote End ---

As this range is not used by Linux Kernelspace nor Userspace it will have no impact on the behavior of the system.

And still you can access this memory from within linux by its address :)