[U-Boot] U-boot Porting

[Aaron Williams]

Hi Zahid,

I am in charge of U-Boot for OCTEON MIPS. I have not pushed the changes 
back upstream since the amount of code is enormous (over 430K lines of 
code!). Granted, a huge percentage of that is from generated register 
files but it is still a huge amount of code. Just the DRAM 
initialization code is 9600 lines of code for DDR2 and DDR3 support.

We also do things that no other architecture does with U-Boot such as we 
always run in TLB mapped memory. The code is available under GPL but you 
need to contact support at cavium.com. With the TLB mapping it no longer 
matters where U-Boot is loaded in memory. The same U-Boot binary image 
can start executing at any 64K flash boundary in the first 4MB of flash 
(so we support the same image as a failsafe and standard bootloader), 
any 4MB boundary in RAM (when booted over PCI or eJTAG) and out of L2 
cache (our top of trunk copies itself from flash to the L2 cache very 
early on to speed up memory initialization). The TLB mapping also allows 
U-Boot to be copied to the very top of memory since KSEG0 is rather 
limited to only 256MB. This is essential since we can support many GB of 
RAM which otherwise requires 64-bit addressing.

I need to push some of my changes back upstream since I have added some 
drivers for some temperature sensors, power monitors, fixed the AHCI 
driver and added a few features over the standard U-Boot (such as 
dynamically generated prompt support).

-Aaron

On 07/05/2012 04:42 AM, sayed zahid wrote:
> Hi ,
> I have basic knowledge of porting u-boot to a new board. But now i have got
> a task to port u-boot on cavium mips based board. As i know that mips
> architecture is already supported, but will it support all cavium octeon
> mips variants? Please put some light on this. I would be glad if you guys,
> give my some idea to where to start with or suggest some documents which
> will help me understand and port on a new architecture
> Regards
> Zahid
>
>
>
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-- 
Aaron Williams
Software Engineer
Cavium, Inc.
(408) 943-7198  (510) 789-8988 (cell)