Hello,
--- On Thu, 1/4/10, Detlev Zundel dzu@denx.de wrote:
From: Detlev Zundel dzu@denx.de Subject: Re: [U-Boot] Saving environment variables in MMC To: nitinm76@yahoo.com Cc: "U-Boot user list" u-boot@lists.denx.de Date: Thursday, 1 April, 2010, 5:35 PM Hi Nitin,
It is rather common to write to the U-Boot
environment in projects
for example to switch to a new set of kernel+file
system after an
update from within linux for the next boot.
My use case is exactly same, to switch to a new set of
kernel+fs after
an update for the next boot.
I also have another usecase of updating the env
variable 'bootargs' if
required in the field. So this use-case combined with
fw_env, what is
your feedback?
It is doable of course. Maybe if I did not mention it before, I advise using a redundant environment for such procedures so that even a powerloss during this upgrade will not brick the device.
Can I get some pointers to some example implementation of a redundant environment. I mean how does a switching between the environments happen? Who clears or sets the obsolete flag for the redundant env?
-Nitin
Could you give me some pointers on upgrading u-boot
itself, but I
don't have a spare partition for that. I would have to
replace working
copy itself?
I would not recommend upgrading U-Boot in the field. As it is not possible to build in redundancy for U-Boot (on most systems I know), there is always the possibility to kill the device with such an update.
I would wanted to have more info(in addition to what I
have
implemented) regarding the failsafe upgrade mechanisms
for
embedded-linux apps and kernel? Could you please point
me to right
forums regarding this. I understand that this is not
specific to
u-boot, but just give me some pointers.
I'm sorry that I cannot point you to a ready to use recipe here, as this really depends on your strategy regarding upgrades, i.e. will you do the upgrade from within Linux? (judging by your questions, you will...) Do you have enough ressources to keep two self-contained "program images" (at least kernel+dtb+rootfs) so you can always update "the other half"? If not, you will probably want to build a non-upgradeable fallback system which is only capable to update "the other part".
As you see, solving your problem really requires you to define your problem more rigorously first.
In order to protoect against interrupts during the update, you may very well want to have a watchdog on your system and use the "bootcount" (grep the documentation for it) feature of U-Boot to detect failing boot attempts.
I hope this is enough to get you started.
Cheers Detlev
-- Thanks so much for Emacs. What a wondrous system -- one of the real seven wonders of the world. Forced to choose between Emacs and, say, any pyramid, I'd take Emacs. -- Robert Boyer -- DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-40 Fax: (+49)-8142-66989-80 Email: dzu@denx.de
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