kernel-packages team mailing list archive

[Adam Smith <1377878@xxxxxxxxxxxxxxxxxx>]

This is caused by the radeonfb kernel module being now compiled as a
module, rather than being 'built-in' to the kernel.  It's hard to see
where/when/why this change happened in Ubuntu, but it probably came from
an upstream kernel change https://bugs.debian.org/cgi-
bin/bugreport.cgi?bug=748398 .

A bit of history: The radeonfb module was purposefully builtin on Ubuntu
PPC to break KMS (as it would cause freezing like above) and also,
radeonfb is necessary for suspend.  UMS was removed entirely from the
radeon xorg driver in 12.10, and people have in fact been using the
fbdev xorg driver (which uses radeonfb) by default.  For most users, KMS
works if forcing pci mode (agpmode=-1), however Lubuntu-qa had an eMac
user at the time of 12.10 who couldn't use radeon KMS (black screen),
and so if the switch was made to CONFIG_FB_RADEON=m then he would have
had to fail the ISOs.  The kernel configuration of framebuffers/KMS has
hence remained the same from 12.04-14.04

It is not very helpful to mix up 14.04 and 14.10 as has been done in the
confusing discussion above.  The kernel configs are different and the
default xorg driver will be different.  Necessary boot parameters will
be different.

The described freezing bug with radeon KMS under PowerPC has been
present for years and has been reported many times.  However, the actual
cause is not known, and those who may have the knowledge to fix it don't
have the hardware or time to devote to a solution.  Forcing pci mode
remains the only workaround to get the radeon xorg driver working on
most machines.

Testing the vivid desktop/live ISO today, I couldn't use radeonfb even
following previoulsy working methods for framebuffer modules
(http://ubuntuforums.org/showthread.php?t=2079873&p=12336938#post12336938
).  It seems video=offb:off doesn't work anymore, although I don't know
why.

Also, I note 'nomodeset' doesn't work.  You have to use radeon.modeset=0
to turn off KMS.

Using fbdev with the openfirmware framebuffer (offb) is not an option
because of the very limited number of colours.

Despite all this, building radeonfb as a module is probably the best
thing to do nowadays, but it will make it harder for some users.

So how can we improve things?  Well, changing the boot.msg on ISOs would
be good!  Currently it says:

 "If the system fails to boot at all (the typical symptom is a white
screen that doesn't go away), use 'live video=ofonly'"

Where this came from has been lost by the sands of time, but it doesn't
relate to any PowerPC mac these days and hasn't been good advice since,
well 10.04, and possibly before that.  Now that framebuffers are modules
(that are blacklisted), the boot parameter video=ofonly in fact does
nothing.  IT HAS TO BE CHANGED as it is just wasting people's time.

It would be far better to point users to the troubleshooting section of
the PowerPC wiki pages:

wiki.ubuntu.com/PowerPCFAQ#Troubleshooting


** Bug watch added: Debian Bug tracker #748398
   http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=748398

** Package changed: linux (Ubuntu) => ubuntu

** Changed in: ubuntu
       Status: Invalid => Confirmed

** Package changed: ubuntu => ubuntu-cdimage

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https://bugs.launchpad.net/bugs/1377878

Title:
  PPC - GUI freezes except for mouse pointer

Status in Ubuntu CD image build software:
  Confirmed

Bug description:
  During the installation the computer freezes completely except for the
  mouse pointer.  And even that is stuck with whatever shape it happened
  to have at the time it froze.  The steps I have to cause the freeze
  are run Ubiquity to start the installation open a terminal, run
  Ubuntu-bug and let it launch Firefox.  It will freeze every time then.
  Even the consoles (ctrl-alt-f1 etc) are unavailable.  What kind of
  information can I collect and how?

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