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hi Marcos,<br>
<br>
I'm not a Google dev, just a hobbyist, but I've spent a lot of time
over the past year working with coreboot for the Haswell ChromeOS
devices (mostly the ChromeBoxes) and can offer some answers, inline
below.<br>
<br>
<div class="moz-cite-prefix">On 5/8/2015 2:38 PM, Marcos Scriven
wrote:<br>
</div>
<blockquote
cite="mid:CA+zKUVLnyJmthe4XnaSiSory6MTHRE15jZk0nJd3WUtHrDnrYA@mail.gmail.com"
type="cite">
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<div>
<div>I have a Dell Chromebook 11 (Google codename 'Wolf')
which I'd like to install a custom coreboot ROM on. Although
John Lewis provides ROMs here <a moz-do-not-send="true"
href="https://johnlewis.ie/custom-chromebook-firmware/rom-download/">https://johnlewis.ie/custom-chromebook-firmware/rom-download/</a>,
I'd rather not use them for a few reasons:</div>
<div><br>
</div>
<div>1) It's replacing one 'closed' ROM with another, in the
sense it's from a 3rd party with no public repo or build
scripts. Although it's possible to extract the coreboot
config used to build them, it's not possible to reproduce
and modify the payloads.</div>
<div>2) I don't need his closed 'Jeltka' payload.</div>
<div>3) I'd like to experiment with other payloads, custom
splash screens etc.</div>
<div>4) I wouldn't learn anything, and I'm interested!</div>
<div><br>
</div>
<div>With that in mind, this guide here looked ideal (although
there's no date on it): <a moz-do-not-send="true"
href="https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/upstream-coreboot-on-intel-haswell-chromebook">https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/upstream-coreboot-on-intel-haswell-chromebook</a></div>
</div>
</div>
</blockquote>
<br>
that's what I started with, and a good overview for what you need to
build your own firmware. I'd suggest however that you first build
coreboot using the same tree/branch as the shipped firmware (which
you linked below) before trying to get upstream coreboot working,
particularly since Wolf hasn't been upstreamed yet. <br>
<br>
Payload wise, SeaBIOS is fine to build from upstream; I build off
the 1.8.1 tag currently. You're welcome to use my configs and build
scripts for reference: <a class="moz-txt-link-freetext" href="https://github.com/MattDevo/coreboot">https://github.com/MattDevo/coreboot</a> and
<a class="moz-txt-link-freetext" href="https://github.com/MattDevo/SeaBIOS">https://github.com/MattDevo/SeaBIOS</a><br>
<br>
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<div><br>
</div>
<div>However, that prompted some questions, which I'm hoping
someone here might be able to help with. (I did ask in the
#chromimum-os IRC channel, but they suggested Google
coreboot developers would be more likely to help here).</div>
</div>
</div>
</blockquote>
<br>
also try #coreboot. I loiter in there and am happy to help if I'm
around (I'm MattDevo on IRC).<br>
<br>
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cite="mid:CA+zKUVLnyJmthe4XnaSiSory6MTHRE15jZk0nJd3WUtHrDnrYA@mail.gmail.com"
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<div><br>
</div>
<div>1) What blobs do I use?</div>
<div><br>
</div>
<div>Although the guide sensibly says to backup the existing
bios with 'flashrom -r', it also says to extract a bios.bin
from /usr/sbin/chromeos-firwmwareupdate (I've posted details
of both at the end). From the latter, it goes on to get you
to extract four blobs:</div>
<div><br>
</div>
<div>- SPI Descriptor</div>
<div>- Management Engine</div>
<div>- MRC</div>
<div>- VBIOS</div>
</div>
</div>
</blockquote>
<br>
that list is correct.<br>
<br>
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<div><br>
</div>
<div>The first discrepancy is that the guide says the
'Management Engine firmware' is only in the latter, but I
was able to use ifdtool on both images to extract the same
set of three files. The flashregion_0_flashdescriptor.bin
files were identical, though the other two were different
despite being the same size.</div>
</div>
</div>
</blockquote>
<br>
The ME firmware isn't always reliably read from a running system, so
using the blob extracted from the shell-ball firmware image is
preferred.<br>
<br>
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<div><br>
</div>
<div>The other thing is there's no reason given as to why one
would use the MRC and VBIOS blobs from the extract, rather
than the backup. Curiously, they are slightly different
sizes (again details below). Looking at the config it seems
the extracted bios image was built with from a Google
coreboot fork four months older than the one backed up from
the machine.</div>
</div>
</div>
</blockquote>
<br>
these should be identical between the backup image and shell-ball
extract. <br>
<br>
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<div><br>
</div>
<div><br>
</div>
<div>2) Which mainboard do I use for the Dell Chromebook 11?</div>
</div>
</div>
</blockquote>
<br>
Wolf<br>
<br>
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<div><br>
</div>
<div>Assuming I have the correct four proprietary blobs, the
next thing is choosing the right mainboard. The guide I link
to mentions suggests 'Falco', but I don't see how, without
knowing the target, such a suggestion could be meaningful?</div>
</div>
</div>
</blockquote>
<br>
Falco is used as an example because it was already upstreamed.
Since Wolf isn't, you would need to do so yourself, which is why I
suggested starting with the stock firmware tree/branch. I
upstreamed Panther, which was somewhat easier since it doesn't have
a built-in display or EC to worry about, but you can use Falco as a
guide, comparing the upstream Falco branch to the shipped firmware
tree/branch, and make similar adjustments for Wolf.<br>
<br>
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<div><br>
</div>
<div>Looking here <a moz-do-not-send="true"
href="https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices">https://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices</a>
Falco appears to be unique to the HP Chromebook 14. The
mainboard codename for my Chromebook is 'Wolf', and that's
not in coreboot upstream.</div>
<div><br>
</div>
<div>Comparing 'src/mainboard/google' in Google's fork, and
coreboot upstream:</div>
<div><br>
</div>
<div><a moz-do-not-send="true"
href="http://review.coreboot.org/gitweb?p=coreboot.git;a=tree;f=src/mainboard/google;h=60045af24d9760f7a52555a5ef6ef3fdc77676b7;hb=HEAD">http://review.coreboot.org/gitweb?p=coreboot.git;a=tree;f=src/mainboard/google;h=60045af24d9760f7a52555a5ef6ef3fdc77676b7;hb=HEAD</a></div>
<div><a moz-do-not-send="true"
href="https://chromium.googlesource.com/chromiumos/third_party/coreboot/+/firmware-wolf-4389.24.B/src/mainboard/google/">https://chromium.googlesource.com/chromiumos/third_party/coreboot/+/firmware-wolf-4389.24.B/src/mainboard/google/</a></div>
<div><br>
</div>
<div><br>
</div>
<div>It seems there is at least some attempt to merge
upstream, and yet wolf isn't there. Is there a particular
reason some mainboards are missing? Did Google stop doing so
for some reason?</div>
</div>
</div>
</blockquote>
<br>
To my knowledge, upstreaming boards during the Haswell days wasn't a
priority, and was often done by non-Google devs (like me) who
happened to have a particular device. Within the last ~6 mos this
has changed significantly, and there's been a large push to keep the
two in sync. <br>
<br>
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<div><br>
</div>
<div>I also note the Google keep the coreboot config source
controlled: <a moz-do-not-send="true"
href="https://chromium.googlesource.com/chromiumos/third_party/coreboot/+/firmware-wolf-4389.24.B/configs/config.wolf">https://chromium.googlesource.com/chromiumos/third_party/coreboot/+/firmware-wolf-4389.24.B/configs/config.wolf</a></div>
</div>
</div>
</blockquote>
<br>
as per above, use that config to build from that branch.<br>
<br>
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<div><br>
</div>
<div><br>
</div>
<div>Thanks</div>
<div><br>
</div>
<div>Marcos</div>
<div><br>
</div>
<div><br>
</div>
<div>--- Some further ROM details ---</div>
<div><br>
</div>
<div>bios extracted with 'flashrom -r' from my Dell Chromebook
11:</div>
<div><br>
</div>
<div>chromebook11.rom: 8192 kB, bootblocksize 3144, romsize
8388608, offset 0x700000</div>
<div>alignment: 64 bytes, architecture: x86</div>
<div><br>
</div>
<div>Name Offset Type
Size</div>
<div>cmos_layout.bin 0x700000 cmos_layout
1164</div>
<div>pci8086,0406.rom 0x7004c0 optionrom
65536</div>
<div>cpu_microcode_blob.bin 0x710500 microcode
41024</div>
<div>config 0x71a5c0 raw
5536</div>
<div>fallback/vboot 0x71bbc0 stage
15083</div>
<div>(empty) 0x71f700 null
2136</div>
<div>fallback/romstage 0x71ff80 stage
42497</div>
<div>fallback/coreboot_ram 0x72a600 stage
91450</div>
<div>fallback/payload 0x740b80 payload
54898</div>
<div>u-boot.dtb 0x74e240 mrc_cache
7919</div>
<div>(empty) 0x750180 null
327192</div>
<div>mrc.bin 0x79ffc0 spd
190180</div>
<div>(empty) 0x7ce700 null
120984</div>
<div>spd.bin 0x7ebfc0 spd
1536</div>
<div>(empty) 0x7ec600 null
77144</div>
<div><br>
</div>
<div>Extracting config shows "# This image was built using git
revision 52034fc1537d4a38e792e700cbc8e9dd1fc36a9c", which is
a commit hash from Google's fork:</div>
</div>
</div>
</blockquote>
<br>
I'd start with this one, or whatever the latest commit is for that
branch.<br>
<br>
<blockquote
cite="mid:CA+zKUVLnyJmthe4XnaSiSory6MTHRE15jZk0nJd3WUtHrDnrYA@mail.gmail.com"
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<div><br>
</div>
<div>commit cef55018e4e936af9a758675353e332df4d9d1a6</div>
<div>Author: David Wu <<a moz-do-not-send="true"
href="mailto:David_Wu@quantatw.com">David_Wu@quantatw.com</a>></div>
<div>Date: Tue Apr 29 12:59:04 2014 -0700</div>
<div><br>
</div>
<div><br>
</div>
<div>bios extracted from the chromeos-firwmwareupdate utility
(which on my machine is a 7.7M binary built on 27th Apr this
year):</div>
<div><br>
</div>
<div>bios.bin: 8192 kB, bootblocksize 3144, romsize 8388608,
offset 0x700000</div>
<div>alignment: 64 bytes, architecture: x86</div>
<div><br>
</div>
<div>Name Offset Type
Size</div>
<div>cmos_layout.bin 0x700000 cmos_layout
1164</div>
<div>pci8086,0406.rom 0x7004c0 optionrom
65536</div>
<div>cpu_microcode_blob.bin 0x710500 microcode
43072</div>
<div>config 0x71adc0 raw
5536</div>
<div>fallback/vboot 0x71c3c0 stage
15083</div>
<div>(empty) 0x71ff00 null 88</div>
<div>fallback/romstage 0x71ff80 stage
42497</div>
<div>fallback/coreboot_ram 0x72a600 stage
91491</div>
<div>fallback/payload 0x740bc0 payload
54898</div>
<div>u-boot.dtb 0x74e280 mrc_cache
7919</div>
<div>(empty) 0x7501c0 null
327128</div>
<div>mrc.bin 0x79ffc0 spd
191020</div>
<div>(empty) 0x7cea40 null
120152</div>
<div>spd.bin 0x7ebfc0 spd
1536</div>
<div>(empty) 0x7ec600 null
77144</div>
<div><br>
</div>
<div>Extracting config shows "# This image was built using git
revision 52034fc1537d4a38e792e700cbc8e9dd1fc36a9c", which is
also a commit hash from Google's fork, but older:</div>
<div><br>
</div>
<div>commit 52034fc1537d4a38e792e700cbc8e9dd1fc36a9c</div>
<div>Author: Marc Jones <<a moz-do-not-send="true"
href="mailto:marc.jones@se-eng.com">marc.jones@se-eng.com</a>></div>
<div>Date: Thu Dec 12 13:13:30 2013 -0700</div>
<div><br>
</div>
<div><br>
</div>
<div>Differences in SPI/ME from backed up ROM and the one
extracted from firmwareupdate tool:</div>
<div><br>
</div>
<div>marcosscriven@ubuntuvm:~/coreboot/util/ifdtool$ ls -altr
frombackup/</div>
<div>total 8200</div>
<div>-rw-r--r-- 1 marcosscriven marcosscriven 6291456 May 8
19:20 flashregion_1_bios.bin</div>
<div>-rw-r--r-- 1 marcosscriven marcosscriven 4096 May 8
19:20 flashregion_0_flashdescriptor.bin</div>
<div>-rw-r--r-- 1 marcosscriven marcosscriven 2093056 May 8
19:20 flashregion_2_intel_me.bin</div>
<div>drwxrwxr-x 2 marcosscriven marcosscriven 4096 May 8
19:20 .</div>
<div>drwxrwxr-x 4 marcosscriven marcosscriven 4096 May 8
19:21 ..</div>
<div><br>
</div>
<div>marcosscriven@ubuntuvm:~/coreboot/util/ifdtool$ ls -altr
fromextract/</div>
<div>total 8200</div>
<div>-rw-r--r-- 1 marcosscriven marcosscriven 6291456 May 8
19:20 flashregion_1_bios.bin</div>
<div>-rw-r--r-- 1 marcosscriven marcosscriven 4096 May 8
19:20 flashregion_0_flashdescriptor.bin</div>
<div>-rw-r--r-- 1 marcosscriven marcosscriven 2093056 May 8
19:20 flashregion_2_intel_me.bin</div>
<div>drwxrwxr-x 4 marcosscriven marcosscriven 4096 May 8
19:21 ..</div>
<div>drwxrwxr-x 2 marcosscriven marcosscriven 4096 May 8
19:21 .</div>
<div><br>
</div>
<div>marcosscriven@ubuntuvm:~/coreboot/util/ifdtool$ diff
frombackup/ fromextract/</div>
<div>Binary files frombackup/flashregion_1_bios.bin and
fromextract/flashregion_1_bios.bin differ</div>
<div>Binary files frombackup/flashregion_2_intel_me.bin and
fromextract/flashregion_2_intel_me.bin differ</div>
</div>
</div>
</blockquote>
<br>
the bios.bin isn't applicable (just the firmware descriptor and ME);
as I noted above, the ME extracted from a running system will differ
slightly.<br>
<br>
Good luck!<br>
<br>
cheers,<br>
Matt<br>
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