Xilinx Zynq-7000 : Help petalinux patch u-boot env vars

Xilinx Zynq-7000 : Help petalinux patch u-boot env vars

[RisingEdgeIndustries]

Hello,

I'm trying to update some of the u-boot environment variables when I build
my linux Image using petalinux for the zynq 7000 (zedboard).

Looking at the configs folder I found the "xilinx_zynq_virt_defconfig".  So
my first question is the following.  Does this file contain the environment
variables I see when I boot u-boot?  I want to add some environment
variables for u-boot.

For example,
ipaddr = <my_ipaddr>
serverip = <tftp_server_ip>
etc....

If this file is not the file one would modify could someone point me to the
correct place?

My ultimate goal is to use petalinux-devtool (which is yocto devtool -
https://docs.yoctoproject.org/ref-manual/devtool-reference.html) to update
u-boot so it contains my added environment variables.  This tool basically
downloads the xilinx u-boot repo and allows changes to be made via the
yocto devtool.  So that is a little background on why I'm trying to do this
modification this way.  The recommended approach from my silicon vendor
(Xilins) is to use this devtool to "patch" the u-boot source.

So long story short, I have the source ready to be patched and built but I
don't know exactly what to patch (which source file) so when I boot into
u-boot I have the newly added environment variables loaded.

Thanks for any help!

Robbie Valentine
Electrical Engineer
RisingEdgeIndustries

Re: [SPAM] Xilinx Zynq-7000 : Help petalinux patch u-boot env vars

[Xavier Drudis Ferran]

El Fri, Jun 10, 2022 at 11:32:59PM -0700, RisingEdgeIndustries deia:
> Hello,
> 
> I'm trying to update some of the u-boot environment variables when I build
> my linux Image using petalinux for the zynq 7000 (zedboard).
> 

Hello, not an expert, but I hope I can help and that people correct me i fI 
was to mislead you. 

> Looking at the configs folder I found the "xilinx_zynq_virt_defconfig".  So
> my first question is the following.  Does this file contain the environment
> variables I see when I boot u-boot?  I want to add some environment
> variables for u-boot.
>

No. You mean configs/xilinx_zynq_virt_defconfig, right ?

This file is a summary of the .config file that the U-Boot project proposes to
configure the build for the board. 

When you do 

make xilinx_zynq_virt_defconfig

the file is copied to .config with the rest of options that are
logical consequences of those in the file according to the rules in
diverse Kconfig files. The make/autoconf/whatnot machinery gets them
in .h files, link files... Makefiles recognize some, etc.

So these are build time options. You can change them interactively
(and break things) with 
make nconfig 
for example, and if you want to create a summary of .config like those 
in configs/ do
make savedefconfig
and you could cp the generated defconfig into configs with the proper
name if that was needed.

Environment variables are runtime options. 
 
> For example,
> ipaddr = <my_ipaddr>
> serverip = <tftp_server_ip>
> etc....
> 

Yes those look like environment variables, for runtime. 
Those can be embedded inside the U-Boot binary, and/or U-Boot
can read them from different places. That's decided through
build time options like those in configs/xilinx_zynq_virt_defconfig.

You may want to read doc/usage/environment.rst

> If this file is not the file one would modify could someone point me to the
> correct place?
> 

I'd say this is not the one or only one, but you might get away by
adding some CONFIG_ENV_SOURCE_FILE=x here and then create a new file
board/xilinx/zynq/x.env

Or if you just want to change those variables you listed, you may set
CONFIG_IPADDR, CONFIG_SERVERIP, CONFIG_BAUDRATE, in the file you said. 
But only those that include/env_default.h considers.

> My ultimate goal is to use petalinux-devtool (which is yocto devtool -
> https://docs.yoctoproject.org/ref-manual/devtool-reference.html) to update
> u-boot so it contains my added environment variables.  This tool basically
> downloads the xilinx u-boot repo and allows changes to be made via the
> yocto devtool.  So that is a little background on why I'm trying to do this
> modification this way.  The recommended approach from my silicon vendor
> (Xilins) is to use this devtool to "patch" the u-boot source.
> 

Maybe you want to patch include/env_default.h or (too complex?) build
an external environment file to load at runtime (if you don't need
trust verification) with mkenvimage -r ... and have it put in offset
0xE00000 in your boot media. But then you should add a copy somewhere
(at 0?). Curious that your board has
CONFIG_SYS_REDUNDAND_ENVIRONMENT=y but no CONFIG_ENV_OFFSET_REDUND.


> So long story short, I have the source ready to be patched and built but I
> don't know exactly what to patch (which source file) so when I boot into
> u-boot I have the newly added environment variables loaded.
>

U-Boot is not Perl, but there's more than one way to do it... 

Re: [SPAM] Xilinx Zynq-7000 : Help petalinux patch u-boot env vars

[RisingEdgeIndustries]

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Thank you very much Xavier!  This reply was very helpful.  Yes, you are
correct regarding <configs/xilinx_zynq_virt_defconfig>.

What did you mean by the below statement?



*Or if you just want to change those variables you listed, you may
setCONFIG_IPADDR, CONFIG_SERVERIP, CONFIG_BAUDRATE, in the file you
said.But only those that include/env_default.h considers.*

Specifically, what did you mean by "only those that
include/env_default.h"?  Looking at env_default.h I don't see much.  Are
you saying if I add my own CONFIG_xxx environment vars they also have to be
in the env_default.h file?

I think patching a source file might be the easiest for me because I'm
booting a ramdisk image so I'm not storing any data outside of my image
binary so building these variables into the binary boot image seems ideal
for me.  Also, Xilinx provides a linux image build tool that builds linux
images for their parts and this tool allows you to script in software
patches to source files for u-boot and linux/kernel during the build
process.  This seems to fit into their expectations so I am trying to
figure out how to "patch" (modify) the u-boot source to have to include
some extra environment variables.

So (I think) what I really need to know is what the proper source file to
patch and add these environment variables to would be.  It's a little weird
because there are quite a few environment variables there already I don't
want to erase, I just want to append a couple new ones.

So if I add, for example, CONFIG_IPADDR to my
configs/xilinx_zynq_virt_defconfig is there anything else I would need to
check or do to ensure this flows through the build properly?

I also couldn't find the environment.rst in my docs - took a screenshot
below.  As an aside I'm using a Xilinx version of u-boot from the following
repo.

https://github.com/Xilinx/u-boot-xlnx


[image: image.png]

Thank you again so much for helping me!

Robbie Valentine
Electrical Engineer
RisingEdgeIndustries
(256) 244-4091


On Sat, Jun 11, 2022 at 12:35 PM Xavier Drudis Ferran <xdrudis@tinet.cat>
wrote:

> El Fri, Jun 10, 2022 at 11:32:59PM -0700, RisingEdgeIndustries deia:
> > Hello,
> >
> > I'm trying to update some of the u-boot environment variables when I
> build
> > my linux Image using petalinux for the zynq 7000 (zedboard).
> >
>
> Hello, not an expert, but I hope I can help and that people correct me i
> fI
> was to mislead you.
>
> > Looking at the configs folder I found the "xilinx_zynq_virt_defconfig".
> So
> > my first question is the following.  Does this file contain the
> environment
> > variables I see when I boot u-boot?  I want to add some environment
> > variables for u-boot.
> >
>
> No. You mean configs/xilinx_zynq_virt_defconfig, right ?
>
> This file is a summary of the .config file that the U-Boot project
> proposes to
> configure the build for the board.
>
> When you do
>
> make xilinx_zynq_virt_defconfig
>
> the file is copied to .config with the rest of options that are
> logical consequences of those in the file according to the rules in
> diverse Kconfig files. The make/autoconf/whatnot machinery gets them
> in .h files, link files... Makefiles recognize some, etc.
>
> So these are build time options. You can change them interactively
> (and break things) with
> make nconfig
> for example, and if you want to create a summary of .config like those
> in configs/ do
> make savedefconfig
> and you could cp the generated defconfig into configs with the proper
> name if that was needed.
>
> Environment variables are runtime options.
>
> > For example,
> > ipaddr = <my_ipaddr>
> > serverip = <tftp_server_ip>
> > etc....
> >
>
> Yes those look like environment variables, for runtime.
> Those can be embedded inside the U-Boot binary, and/or U-Boot
> can read them from different places. That's decided through
> build time options like those in configs/xilinx_zynq_virt_defconfig.
>
> You may want to read doc/usage/environment.rst
>
> > If this file is not the file one would modify could someone point me to
> the
> > correct place?
> >
>
> I'd say this is not the one or only one, but you might get away by
> adding some CONFIG_ENV_SOURCE_FILE=x here and then create a new file
> board/xilinx/zynq/x.env
>
> Or if you just want to change those variables you listed, you may set
> CONFIG_IPADDR, CONFIG_SERVERIP, CONFIG_BAUDRATE, in the file you said.
> But only those that include/env_default.h considers.
>
> > My ultimate goal is to use petalinux-devtool (which is yocto devtool -
> > https://docs.yoctoproject.org/ref-manual/devtool-reference.html) to
> update
> > u-boot so it contains my added environment variables.  This tool
> basically
> > downloads the xilinx u-boot repo and allows changes to be made via the
> > yocto devtool.  So that is a little background on why I'm trying to do
> this
> > modification this way.  The recommended approach from my silicon vendor
> > (Xilins) is to use this devtool to "patch" the u-boot source.
> >
>
> Maybe you want to patch include/env_default.h or (too complex?) build
> an external environment file to load at runtime (if you don't need
> trust verification) with mkenvimage -r ... and have it put in offset
> 0xE00000 in your boot media. But then you should add a copy somewhere
> (at 0?). Curious that your board has
> CONFIG_SYS_REDUNDAND_ENVIRONMENT=y but no CONFIG_ENV_OFFSET_REDUND.
>
>
> > So long story short, I have the source ready to be patched and built but
> I
> > don't know exactly what to patch (which source file) so when I boot into
> > u-boot I have the newly added environment variables loaded.
> >
>
> U-Boot is not Perl, but there's more than one way to do it...
>

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