[fedora-arm] Announcing: Fedora ARM Technical Talks

[Sean Omalley]

** What needs to be done in u-boot to support loading DTB

as far as I can tell (so correct me if I am wrong somewhere). 

adding: 

#define CONFIG_OF_LIBFDT 
and possibly (im not sure this might be to use the included dtb files with the uboot source, but they are really kept in the kernel right now.) 

#define CONFIG_DEFAULT_DEVICE_TREE
I usually add for ext4 support also. :) 

#define CONFIG_CMD_EXT4
to u-boot-src/include/configs/boardname.h

On the PogoPlugs You have to muck with the memory addresses since the default environment data is at 0x60000 and the u-boot binary with the dtb is bigger then the 368k so when you do a saveenv it writes over your uboot and crashes :) However the default uboot partition (as defined in uboot itself) starts at 0x0 and ends at 0x100000 (with 20k addresses = 128k) but the environment is 20k addresses, so the max without changing the partition is I think 0x080000. (ie #define CONFIG_ENV_OFFSET               0x80000 /* env starts here */ in the same configs file.)


I have been successful at getting uboot to build and load, and saveenv 
but I haven't gotten a kernel to boot. It acts like it does when you 
have the jtag and do a load but forgot to run nand probe 1 to activate 
it. It pretends to load really fast, but doesn't really work. :) 


To build uboot, I have been using the guruplug with f18, rather then setting up the cross-compiler (which i ran into a bug). I'm getting to the uboot prompt so it seems to be working. :) 


There are few more things I have to look at though to try and get it to work correctly.  


If you aren't worried about trashing the original install on your nand, and have a working jtag or uart serial to load it with, you aren't going to get into too many issues. unless you don't have a working uboot file to reload.. :) 



The initial partitions are set in uboot as well as the load addresses. 






>________________________________
> From: Jon <jdisnard at gmail.com>
>To: Fedora ARM secondary architecture list <arm at lists.fedoraproject.org> 
>Sent: Friday, February 22, 2013 12:06 PM
>Subject: Re: [fedora-arm] Announcing: Fedora ARM Technical Talks
> 
>
>
>
>
>On Fri, Feb 22, 2013 at 3:40 AM, Niels de Vos <devos at fedoraproject.org> wrote:
>
>On Sun, Feb 17, 2013 at 11:55:00PM -0500, Jon Masters wrote:
>>> Hey everyone,
>>>
>>> What would you like my next talk to be on? I will do a hardware debug
>>> session soon, but meanwhile I am open to suggestions for the topic after
>>> this week - this week John Dulaney is talking about Chromebooks!
>>
>>A talk about device-tree would be cool. An into with how to use/load
>>a device-tree blob and extending into explaining how the plain-text
>>files converted in to blobs cause the kernel to load certain drivers and
>>how these drivers know what pins/memory/options/...  to use.
>>
>>
>
>
>This is a great idea.
>Here are some of my thought to add along with Niels':
>
>
>* Building the DTB from source
>** make some changes if you want
>
>
>* loaded DTB
>** Selecting a safe load addr
>** What needs to be doen in u-boot to support loading DTB
>
>
>* Appended DTB
>** Why this is bad
>** Why this is good
>** example of making an appended DTB and booting.
>
>
>* FIT images (chromebook)
>** mkimage -f
>** the dtc utility
>
>
>* /proc/device-tree
>** A guided tour of this new area of /proc
>** how it can be used, it's purpose (besides proving the DTB is loaded and working).
>
>
>
>
>
>
>It would be great to show the audience some use of Device Tree that help them at a personal level, besides being able to boot their device.
>For example, I believe the Pandaboard was used as an example early on of how to use DTB to set a persistent mac address.
>I'm not sure there are any other things the audience might ever want to customize in their DT, but it would be nice to share as many as possible.
>
>
>
>
>
>-- 
>
>-Jon Disnard
>irc: masta
>fas: parasense
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