[Libreboot-dev] MacBook2,1 bug hunt

[Albin]

Hi,

I've compiled and flashed a series of old revisions of the
MacBook2,1 port and have managed to pinpoint at least one of
the bug-inviting commits.  All of the binaries tested were of
the type "macbook21_svenska_vesafb".

Bug descriptions
================

Depending on the git revision, one or more of the following
bugs may be present.

a) The front light doesn't turn itself off directly after boot
   (as it should)
b) Three instances of
   `--MORE--Unknown key 0xbf detected` (or `be` `80` `f8`, etc.)
   are printed over the GRUB menu entries.
c) A list of `--MORE--Unknown key 0xff detected` is printed all
   over the screen when booting with a USB storage device
   connected and, after a while, the computer reboots.
d) The menu entry `Search for GRUB configuration (grub.cfg)
   outside of CBDS` doesn't find any grub.cfg files even when
   they are present.
e) The first menu entry (Load Operating System) doesn't boot
   a previously installed Trisquel 7 (on my computer) but
   instead shows just the libreboot background and the computer
   freezes.

Bugs present in various revisions
=================================

The revisions (R) tested are the following, named 0—8. I didn't
compile 0 myself but here only used the official stable binary.

|===========================================|
| R | Date and time     | a | b | c | d | e |
|===|=======================================|
| 0 | 2015-05-18-stable | x | x |   |   |   |
|---|---------------------------------------|
| 1 | 2015-06-14:17:02  |   |   |   |   |   |
|---|---------------------------------------|
| 2 | 2015-06-15:20:15  |   |   |   |   |   |
|---|---------------------------------------|
| 3 | 2015-09-03:03:09  |   | x |   |   |   |
|---|---------------------------------------|
| 4 | 2015-10-06:23:25  |   |   | x |   |   |
|---|---------------------------------------|
| 5 | 2015-10-06:23:40  |   | x |   | x | x |
|---|---------------------------------------|
| 6 | 2015-11-29:22:56  |   |   |   | x | x |
|---|---------------------------------------|
| 7 | 2015-12-15:23:15  |   |   |   | x | x |
|---|---------------------------------------|
| 8 | 2016-01-23:06:37  |   |   |   | x |   |
|--------------------------------------------

Commit IDs
==========

1: 9f8eced929a99b2ad7b10d1b8d237779afdd98d5
2: bd95009839337576c1d7ac6d022228c4ec4248a5
3: 90f78aa949d913c33c066245c71b18ec1e31173c
4: 5dad7b53413384d1a93180dacbc51f3480bb3300
5: d0c54b9ca11bdcae0b179d21028c722aeb9f9095
6: a6a7f8723564a67bc10c6f879fde528589a6521b
7: 48821e53b0d6c367d743bb1f1ea4f4da983b9d08
8: bcf3ffdfe2ea88e34a915be3a08b04b2d8ec2c8e

Discussion of results
=====================

a) seems to have been fixed once and for all since the last
stable release.

b) and c) seem to come and go and I have no idea why.  For some
of the binaries above I flashed them twice and rebooted multiple
times to see if maybe these bugs would appear only sometimes.
Every time, however, the bugs presented themselves in the same way.

d) and e) are closely related; they must have been introduced with
revision 5 ("Merge kl3's GRUB enhancements from autoboot") because
revision 4 from earlier the same day didn't have them.  At one point,
between 7 and 8, e) disappeared (I don't know why).

Suggestion
==========

See the end of the commit diff for revision 5:

https://libreboot.org/gitweb/?p=libreboot.git;a=commitdiff;h=5dad7b53413384d1a93180dacbc51f3480bb3300

If the code related to

`menuentry 'Search for GRUB configuration (grub.cfg) outside of CBFS`

were reverted to its previous state, then maybe the next stable
MacBook2,1 release could be free from all of the bugs discussed
in this report.


Happy hacking!

Albin

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