Embedded Linux start-up options from Uboot
 

Hi guys,
First of all, sorry that this question could not be related to the current thread, I'm quite new to this forum.

I have an embedded linux(arago project) starting on a custom device. I see the following parameters set inside uboot.

bootargs=mem=32M@0xc0000000 mem=56M@0xc4000000 console=ttyS2,115200n8 root=/dev/ram0 rw initrd=0xc4000000,15M ramdisk_size=49152 ip=192.168.2.11

bootcmd=nand read.e 0xc4000000 0x400000 0xdf0000; nboot.e 0xc0700000 0 0x200000; bootm

As far as I understand 56+32M are allocated for Linux in disjoint areas inside RAM. And there is a initram of 15M. I believe 15M is a size of compressed rootfs, after gunzip it's about 46M. But what about ramdisk_size option...does it mean that ram disk in total has 49M capacity...hm, then what about 56+32-49M ? What are they for? Are they wasted?

I've tried to increase ramdisk_size up to 90M and everything works fine. I googled for several days for some explicit explanations but I didn't get the idea of this setup.

Please, can anybody explain me how this thing works?

Looking forward to hearing from you in the earliest time...I'm really in stuck.

Hi Dmitry,

Can you be more specific about which arago kernel you're using?

Project sources can be found at http://arago-project.org/git/projects/

In general, the Linux Kernel has a "Documentation" folder at the root of the source which can be perused for options. Additionally, one can grep for specific options of interest. e.g.

The Kernel documentation is also fairly logical. e.g. to learn anout memory look at memory.txt. To learn about ramfs one can look in the filesystems folder.

For things you're not sure about the location you can clone the source and use grep to find it.

Edit: found ramdisk_size in the kernel docs by web searching "kernel.org ramdisk_size". It seems the option is in KB so 49152 is 48MB.