UBootFdtInfo < U-Boot

---+!! Flattened Device Tree

The mandate of the Flattened Device Tree custodian repository is to improve fdt "blob" support in u-boot.  It does this by adapting David Gibson's libfdt for use in u-boot and adds a =fdt= command to allow easy manipulation of "fdt blobs."

---

%TOC%

---++ Branches / Patches Queued for the Next Window

---++ =libfdt=

Checking for libfdt patches
   1 Clone the dtc
      * =git clone git://git.jdl.com/software/dtc.git=
   1 Find all changes in the libfdt/ subdirectory
      * =git log libfdt/=
   1 Find all the =libfdt/= patchset hashes
      * =git log libfdt/ | awk '/^commit/ {print $2}'=

---+++ <nop>ToDo - =libfdt=

Ongoing: Catch up with =dtc= (=libfdt/*= to be slightly more explicit).

   * Upstream libfdt patchsets applied to the v2011.09 release:
      * 0329-Support-ePAPR-compliant-phandle-properties.patch
         * DTC commit: d75b33af676d0beac8398651a7f09037555a550b
         * U-Boot commit 05a22ba096fb996bb69ab020a8d08aafac2c28ba
      * 0344-libfdt-Implement-property-iteration-functions.patch
         * DTC commit 73dca9ae0b9abe6924ba640164ecce9f8df69c5a
         * U-Boot commit d1c6314887c4d6712f7bd9ba7428b6517e7732e0
   * =Fix-a-possible-overflow-case-detected-by-gcc-4.3.2.patch= - This upstream patch was applied to u-boot:
<blockquote>
<verbatim>
commit 13d93f38e86818739317b0206d597265cf9e675e
Author: Emil Medve <Emilian.Medve@Freescale.com>
Date:   Mon Feb 23 10:43:36 2009 -0600
</verbatim>
</blockquote>

---++ Outstanding Patches


---++ <nop>ToDo

   1 For =fdt addr=, enhance to implement "fdt addr X +Y", where "Y" is the number of additional bytes to _add_ to the blob.
   1 Suggestion from Timur: <blockquote>\
If the device tree is wrapped in a uimage (a 'dtu'), then the hdr->ih_load field contains the location where the device tree should be copied.  If that value is zero, bad things happen.  So I have two suggestions: <ol>\
      <li> If the value is zero, report an error and stop\
      <li> If the value is zero, assume the user doesn't want the device tree to be copied, and the code should fill it in with the current location of the device tree.</ol> I like option #2 better, because then I don't have to hard-code an address into the dtu.</blockquote>
   1  Save and load the blob to flash (likely after env space)
      * Add a CRC a'la env
      * Add a backup version a'la env 
   1 Proposed additional =fdt= commands
      * =merge= - merge two trees.  Need a conflict resolution: source tree #1 has priority?
         * David Gibson has talked about creating a "[[http://article.gmane.org/gmane.linux.ports.ppc64.devel/35740][graft]]" function for libfdt.
      * =load= - load from flash
         * Not needed, see =fdt move= (but non-memory mapped storage such as NAND flash won't work with =fdt move=)
      * =save= - save to flash 
         * =cp= should handle this already
      * =header= - print useful blob info like validity, version, total and used reserved slots, extra space, presence of &lt;NOP&gt; filling(?), etc.
         * Kumar submitted a patch to print the header info... some additional info showing extra space would be useful.

NOTE: Grant Likely has adapted =libfdt= for the 5xxx family, his methodology is the recommended template.

---++ Background Information on Flattened Device Trees

1275 spec:
   * http://playground.sun.com/pub/1275/coredoc/1275-1994/1275.ps.gz 

Power.org&trade; Standard for Embedded Power Architecture&trade; Platform Requirements (ePAPR)
   * https://www.power.org/documentation/epapr-version-1-1/
     %BR% (registration needed)

!PowerPC processor binding:
   * http://playground.sun.com/1275/bindings/ppc/release/ppc-2_1.html 

booting-without-of.txt
   * In the kernel source tree under =Documentation/powerpc=) - Describes the flat device tree as it is used in the Linux kernel.

Device Trees Everywhere-- paper by David Gibson and Ben Herrenschmidt-- an overview of the concept
   * http://ozlabs.org/~dgibson/home/papers/dtc-paper.pdf 

PCI Bus binding:
   * http://playground.sun.com/1275/bindings/pci/pci2_1.pdf 

USB Bus binding:
   * http://playground.sun.com/1275/bindings/usb/usb-1_0.ps 

CHRP Binding:
   * http://playground.sun.com/1275/bindings/chrp/chrp1_8a.ps
   * (I think some things we may use like interrupt controller device types came from here) 

64-bit extension:
   * http://playground.sun.com/1275/bindings/64bitx/12756d5.ps 

Interrupt mappings ( very important ):
   * http://playground.sun.com/1275/practice/imap/imap0_9d.html 

Misc device types (network, RTC, sound, etc)
   * http://playground.sun.com/1275/practice/devicex/dse1_0a.html

---++ Notes

---+++ All Your Base are Belong to Us

...aka some more git usage...

<pre><tt>\
# See what branch I'm on (it happens to be master)
git branch

# Switch to my "sync with Wolfgang" branch (use -b the first time)
git checkout uboot

# Pull the latest u-boot.git (supreme master) changes into my uboot branch
git pull git://www.denx.de/git/u-boot.git

# Switch back to my master branch (where my pending changes are/would be)
git checkout master

# Rebase against u-boot.git latest
git rebase uboot

# Want to see what Kumar Gala is cooking with libfdt - start a new branch
git checkout -b galak

# Pull Kumar's libfdt branch
git pull git://git.kernel.org/pub/scm/boot/u-boot/galak/u-boot.git libfdt

# See what the changes are
git diff master

# Visual version
gitk

# Rebase against the master (which was rebased against Wolfgang's supreme 
# master), our (Kumar's) changes are now against the master.
git rebase master
</pre></tt>


---+++ Testing (not fdt-specific)

   * See DENX Universal Test System ([[http://git.denx.de/?p=duts.git;a=summary][DUTS]])

   * Debian python pexpect and pyserial packages:
      * python-pexpect - http://pexpect.sourceforge.net/pexpect.html
      * python-serial - http://pyserial.sourceforge.net/

<pre>
>>> import serial
>>> ser = serial.Serial(0, 115200, timeout=100, parity=serial.PARITY_NONE, rtscts=0)
>>> ser.write("help\n")
>>> ser.inWaiting()
2304L
>>> s=ser.read(2304)
>>> print s
help
?       - alias for 'help'
askenv  - get environment variables from stdin
:
:
version - print monitor version
=> 
>>> ser.write("help\n")
>>> s = ser.read(100)
>>> print s
help
?       - alias for 'help'
askenv  - get environment variables from stdin
autoscr - run scri
>>> s = ser.readline()
>>> print s
pt from memory
>>> s = ser.readline()
>>> print s
base    - print or set address offset
</pre>