Bug#822575: fb: switching to cirrusdrmfb from simple

Source: linux
Version: 4.9~rc5-1~exp1
Followup-For: Bug #822575

Dear Maintainer,

I have the same problem with cirrusfb: After that last message the
screen does not update anymore (but I can login through ssh).

After lots of research I things the problem is related to
CONFIG_X86_SYSFB being enabled in Debian by default:

$ git rev-parse HEAD # git://anonscm.debian.org/kernel/linux.git
6c0c9bcf78dfc886907d006b8cb6c2ea0f075a62
$ git grep -n -F -e CONFIG_X86_SYSFB -e CONFIG_FB_SIMPLE
config/armhf/config:1187:CONFIG_FB_SIMPLE=y
config/kernelarch-x86/config:73:CONFIG_X86_SYSFB=y
config/kernelarch-x86/config:1776:CONFIG_FB_SIMPLE=y

By default the video RAM is claimed by the boot framebbuffer:

# cat /proc/fb
0 simple
# grep 80000000 /proc/iomem
80000000-febfffff : PCI Bus 0000:00
  80000000-81ffffff : 0000:00:02.0
    80000000-801d4fff : BOOTFB

When cirrusdrmfb loads, it disabled the bootfb and tries to claim that
region. As it is still held by bootfb, this failes:

# modprobe cirrus
# dmesg
[  263.171744] checking generic (80000000 1d5000) vs hw (80000000 2000000)
[  263.171753] fb: switching to cirrusdrmfb from simple
[  263.171838] Console: switching to colour dummy device 80x25
[  263.177052] [drm:cirrus_device_init [cirrus]] *ERROR* can't reserve VRAM
[  263.177066] cirrus 0000:00:02.0: Fatal error during GPU init: -6
[  263.177072] Trying to free nonexistent resource <0000000082029000-0000000082029fff>
[  263.177080] Trying to free nonexistent resource <0000000080000000-0000000081ffffff>

/proc/fb is empty afterwards, as bootfb remains disabled.

My solution was to remove cirrus.ko and cirrusfb.ko from
/lib/modules/`uname -r`/kernel/ and to re-build the initramfs. That
prevented cirrus from being loaded, leaving the simple-frame-buffer intact.
Loading the module by hand breaks the console again.

I found that SUSE bug
<https://bugzilla.novell.com/show_bug.cgi?id…5821>, where Takashi Iwai
finally disabled those options for OpenSUSE.

Ubuntu disabled the Cirrus drm driver first,
<https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1038055>
but later changed to only disable X86_SYSFB.

So probably it's best to disable X86_SYSFB:

config X86_SYSFB
	bool "Mark VGA/VBE/EFI FB as generic system framebuffer"
	help
	  Firmwares often provide initial graphics framebuffers so the BIOS,
	  bootloader or kernel can show basic video-output during boot for
	  user-guidance and debugging. Historically, x86 used the VESA BIOS
	  Extensions and EFI-framebuffers for this, which are mostly limited
	  to x86.
	  This option, if enabled, marks VGA/VBE/EFI framebuffers as generic
	  framebuffers so the new generic system-framebuffer drivers can be
	  used on x86. If the framebuffer is not compatible with the generic
	  modes, it is adverticed as fallback platform framebuffer so legacy
	  drivers like efifb, vesafb and uvesafb can pick it up.
	  If this option is not selected, all system framebuffers are always
	  marked as fallback platform framebuffers as usual.

	  Note: Legacy fbdev drivers, including vesafb, efifb, uvesafb, will
	  not be able to pick up generic system framebuffers if this option
	  is selected. You are highly encouraged to enable simplefb as
	  replacement if you select this option. simplefb can correctly deal
	  with generic system framebuffers. But you should still keep vesafb
	  and others enabled as fallback if a system framebuffer is
	  incompatible with simplefb.

	  If unsure, say Y.

If you read <https://patchwork.kernel.org/patch/3380911/> there was a
patched proposed to change it to 'N' and/or to depend on FB_SIMPLE, but
that patch never made it into linux.

Nor did <https://patchwork.kernel.org/patch/3368351/> or
<https://patchwork.kernel.org/patch/3528991/>.

I tried to contact David Herrmann himself, but never got a reply.

So I think Debian should disable X86_SYSFB for now, too.

Thank you for your work and help
Philipp "also a Debian maintainer" Hahn
-- System Information:
Debian Release: 8.6
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable'), (90, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 3.16.0-4-amd64 (SMP w/4 CPU cores)
Locale: LANGÞ_DE.UTF-8, LC_CTYPEÞ_DE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)