** 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@gmail.com>
To: Fedora ARM secondary architecture list <arm@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@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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