Migrating XO-1.75 to device tree - upgrade considerations

[Jerry Vonau]

On Wed, 2012-08-22 at 09:53 -0600, Daniel Drake wrote:
> On Tue, Aug 21, 2012 at 4:06 PM, Jerry Vonau <jvonau at shaw.ca> wrote:
> > While working with Australia, we have found the need to have the AC
> > plugged-in for a firmware update while not requiring AC for a image
> > upgrade to be problematic in the field. You can start an OS upgrade then
> > run out of battery leaving a incomplete upgrade, while an AC adaptor may
> > not always be available to use while your employing charging racks. We
> > make our signed firmware available for download outside of the image, to
> > enable the firmware to be installed from a USB drive before updating the
> > OS. We disable the AC check and force a minimum 50% battery level before
> > either actions can occur with our custom olpc.fth script which is part
> > of our One Education USB[1] project. To my knowledge we have not bricked
> > any XOs in the field using this method.
> 
> Is this driven because your OS update process is not resilient to power failure?
> 

No, once upon a time the official OLPC upgrade process was not resilient
to power failures[1][2].

> Either way, I don't quite understand the situation involving the
> firmware here. (Maybe until now) there has been no driving need to
> upgrade firmware when upgrading OS releases - it can be done before,
> after, 3 weeks after, doesn't make a big difference. 

Yes it did at one point, way back when sparse support was first added to
the .zd files in order to gain the speed advantage offered the required
firmware must be installed first.

> Or is there a
> reason I'm missing for why you go to special lengths to make sure the
> firmware upgrade is done first?
> 

After an OS upgrade we can't expect a teacher to boot each XO with an AC
adapter plugged-in when there maybe only one adaptor available for the
class or no AC at all because of the use of alternate charging methods.
I wonder how this is handled in other deployments that are using
solar-panels or hand cranks because there is no AC available. We have
chosen to have the firmware installed from a USB drive as we can disable
the AC check, and use the charge level of the battery to ensure there is
enough power present to ensure success with the updating processes with
our olpc.fth script.

Jerry

1. http://lists.laptop.org/pipermail/devel/2012-April/034836.html
2. http://dev.laptop.org/ticket/11776