[flashrom] Trouble disabling write-protection on Chromebook
dhendrix at google.com
Wed Dec 18 23:56:01 CET 2013
On Mon, Dec 16, 2013 at 9:09 PM, <
BM-2cWKH3wgq8zXX9eHfba16oTc8b61ead4Yq at bitmessage.ch> wrote:
> >> As root in
> >> developer mode, the output of flashrom -v is "flashrom v0.9.4 : 4169bc8
> >> ...". The first time I ran flashrom --wp-disable, I got a message saying
> >> the operation FAILED with error=1. At that point I took the board apart
> >> again and cleaned the write-protect screw hole with q-tips dipped in
> >> rubbing alcohol. When I reassembled the Chromebook and tried again with
> >> flashrom -V --wp-disable, the last few lines I receive are:
> >> w25_set_srp0: old status: 0xb8
> >> w25_set_srp0: new status: 0xb8
> >> w25q_disable_writeprotect(): error=1.
> >> No -i argument is specified, set ignore_fmap.
> >> FAILED
> >> restore_power_management(): Power management enabled
> >> As you can see, I can't seem to disable write protection on this chip.
> >> I'm
> >> running stock ChromeOS. Any idea what I might be doing wrong? Thanks in
> >> advance.
> > That's weird... Since you have the system taken apart already, can you
> > disconnecting the battery while the machine is unplugged? I'd recommend
> > leaving it disconnected for a minute or so, the idea being to give the
> > ROM enough time to fully discharge and reset.
> Thanks for responding. I took your advice and disconnected the battery for
> several minutes. After reassembling the board and running flashrom
> --wp-disable again I am receiving the same message (FAILED). flashrom
> --wp-status says:
> WP: status: 0x00b8
> WP: status.srp0: 1
> WP: status.srp1: 0
> WP: write protect is enabled.
> WP: write protect range: start=0x00000000, len=0x00200000
Hmmm, that looks correct for normal circumstances (with write-protection
enabled). Flashrom *should* be able to clear bit 7 of SRP0, so the status
should show up be 0x38 after running with --wp-disable.
Can you try running "flashrom -p host --wp-disable -V" and pasting the
output on paste.flashrom.org?
> If you have a voltmeter handy, you can also try measuring the voltage on
> the /WP pin (pin 3). More details on pin configuration can be found in
> > datasheet:
> I don't have voltmeter; I'm sure I could locate one given enough time
> though. Do you have any other suggestions as to steps I might be
> overlooking here? Otherwise, what should I be looking for specifically in
> the Winbond data sheet?
Unfortunately I don't have many ideas here... I've only seen this once and
it seemed to be a defective chip since I couldn't change the write-protect
status by removing the chip and using an external programmer. (This was on
a different machine, and not in a retail unit)
The only reason for failure should be if there is anything bridging the gap
between the copper pads around the write-protect screw hole, thereby
connecting /WP on the chip to ground. If you have a magnifying glass, can
you inspect just to make sure there is nothing connecting those pads? I
assume that since you cleaned the area with rubbing alcohol that there is
no residue from the sticker. I'm wondering if there is a tiny bit of copper
(perhaps from a manufacturing defect) bridging the gap. If so, I'll ask one
of our hardware engineers if it's safe to attempt severing it or if they
have any better ideas.
David Hendricks (dhendrix)
Systems Software Engineer, Google Inc.
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