What are ATAGs for a device that uses Linux Kernel?
I am trying to understand how a kernel boots. I am currently trying to port a new kernel to hTC Incredible S VIVO (s710e) device, but I cannot get it to boot. So, I looked into the device's original kernel, and looked through some documentation, and found out that the device uses ATAGs. Now, I have several questions that I cannot find a clear answer for:
- What are ATAGs?
- What are they used for?
- How does the kernel boot using ATAGs?
- Do ATAGs play a vital role in booting a kernel?
Answer
ATAGS are ARM tags. They are used to carry information such as memory size from boot code to kernel. Some references (which in turn lead to other references): booting standards, customized ATAG.
This reference arm/Booting explains theory, but does not much tell a user what to do.
On my target I use the following in my U-Boot config: CONFIG_CMDLINE_TAG, CONFIG_SETUP_MEMORY_TAGS, and these in my kernel config: CONFIG_ATAGS=y, CONFIG_USE_OF is not set. Not sure if that is sufficient for you but it gives you clues to search on, good luck.