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Re: [Libreboot] Bricked my c201

From: Paul Kocialkowski
Subject: Re: [Libreboot] Bricked my c201
Date: Tue, 16 Feb 2016 16:31:58 +0100


sorry for the late answer,

Le mardi 19 janvier 2016 à 14:41 +0100, Albin a écrit :
> > Either way, it's hard to find out exactly why it's refusing to boot
> > externally, provided that Libreboot still shows the warning about
> > external media booting being enabled. Still, it is probably either about
> > the kernel you extracted not being in the right format or the partitions
> > not being set up correctly.
> > 
> > Perhaps you could send me the kernel file you extracted (I'm not sure I
> > have a backup of mine) and I could prepare a known-to-work disk image
> > for you to boot from.
> That would be very nice but unfortunately I cannot access the files on
> the USB drive where I saved it. When I insert it into my other (X86_64)
> computer it shows up as an "unknown" device. Besides, external media
> booting has now been switched off as well so I really need to reflash
> the firmware.

What I can do is prepare a "recovery" SPI flash image with external media boot
explicitly enabled and signature verification disabled, as well as a disk image
to dd into an sdcard/usb drive that contains a basic debian rootfs with the
cros-specific tools (that I will soon integrate in Libreboot).

I'll probably write up a blog post with instructions while I'm at it. Hopefully,
I'll find time to do this in the next week. Feel free to remind me soon ;)

> > If that fails, it might mean that you'll have to relfash the SPI flash
> > with an image that allows running unsigned kernels, which will give us
> > more flexibility.
> > 
> > Either way, your device is not lost and I'm confident there will always
> > be a way to straighten it out. If you feel like you don't want to pull
> > this off yourself, we could see about you sending me the device so that
> > I do what's needed to fix it.
> Thank you for the encouragement! I do have an SPI programmer and some
> experience with flashing externally (T60 and macbook2,1) so I would like
> to try to unbrick the c201 myself. Still, I could need some help with
> how to connect the wires to the BBB. I'm familiar with most of the
> abbreviations but I don't know how to connect HOLD#, CLK and CS#. Maybe
> you, or somebody else, could expand the documentation with details about
> BBB wiring, like it's in the other guides.

That's very generic SPI flashing stuff, so I don't think it belongs in the C201
guide in particular. CS# and CLK are signals to connect to the matching ends on
the BB while HOLD# and WP# have to be pulled-up (you can connect them directly
to VCC if you don't care about potential excessive current flowing).

> Another thing that would be useful, I think, is a libreboot
> configuration for veyron_speedy with some of the security features
> switched off. That would give somebody who needs to recover their device
> another option than reinstalling the backed up factory image.

That would be doable by changing some GBB bits, so perhaps we could consider
that. I was more thinking of a quick and dirty code-commenting approach, but if
this can be done cleanly without changing the code too much, why not

Perhaps recovery instructions could be part of the C201 install guide then.

Thanks for your feedback!

Paul Kocialkowski, Replicant developer

Replicant is a fully free Android distribution running on several
devices, a free software mobile operating system putting the emphasis
on freedom and privacy/security.


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