Re: [Libreboot] Bricked my c201

[Paul Kocialkowski]

Hi,

quick status update: I still didn't manage to prepare what I promised weeks ago,
sorry about that. It's unclear when time will allow for it, but I'm not
forgetting about it.

Le mardi 16 février 2016 à 16:55 +0100, Albin a écrit :
> Den 2016-02-16 kl. 16:31, skrev Paul Kocialkowski:
> > sorry for the late answer,
> > 
> No worries!
> 
> > 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).
>
> That would be awesome! As I said above I don't think that I can send you
> my ChromeOS kernel as I'm unable to access the file system on the USB
> drive where I saved it. Would you still be able to pull it off?

Of course! Once you have control over what's on the SPI flash, the rest is no
longer problematic.

> > 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).
>
> I don't understand what you mean about pulling up. I guess that write
> protect isn't necessary since taking out the Screw should be enough, but
> if HOLD# needs to be connected, then I don't know how.

I think removing the screw is enough, the pull resistor is likely already on the
board. It might be the same for HOLD#. If not, just connect a resistor from that
pin to VCC (a few kOhm should do), or just connect the pin directly to VCC if
you're feeling lazy.

> > > 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!
> Thank you!

Cheers,

-- 
Paul Kocialkowski, low-level free software developer on embedded devices

Website: https://www.paulk.fr/
Coding blog: https://code.paulk.fr/
Git repositories: https://git.paulk.fr/ https://git.code.paulk.fr/

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