DDC: no ddc bus - possible BIOS bug

[屋国遥]

Hello, all.

I am trying to make dual-head environment on Mac Pro with Ubuntu
10.10.  My Mac Pro has the Radeon HD 2600 XT graphic card, so I decided
to use the radeon driver.

Now, I connect two monitors (the same SAMSUNG monitors) and boot the
system and X, one display works well, but the other is not recognized.
In dmesg, I found out the following error message.

I googled the message and found
<http://www.mail-archive.com/xorg-driver-ati@lists.x.org/msg16768.html>
and <https://bugs.freedesktop.org/show_bug.cgi?id=29255>.  Referring
to these posts, I upgraded the kernel to 2.6.36
(http://kernel.ubuntu.com/~kernel-ppa/mainline/v2.6.36-maverick/) and
also graphic drivers (https://launchpad.net/~xorg-edgers/+archive/ppa).

However, the same error is displayed.

I am sorry to say that I have no idea how to use Alex's patch to
`radeon_atombios.c' because of my poor knowledge of Linux.
Is not this change included in the recent kernel or drivers?


Because dual-head environment works successfully on Mac, I suspect the
monitor or graphic card has no problem.

The following is some display-related information and settings.
I tried to attach video bios data, but I could not, because echo and cut are
permission denied (of course, I did them as root).
Thank you.

$ dmesg | grep drm
[   11.044447] [drm] Initialized drm 1.1.0 20060810
[   11.490963] [drm] radeon kernel modesetting enabled.
[   11.491845] [drm] initializing kernel modesetting (RV630 0x1002:0x9588).
[   11.491928] [drm] register mmio base: 0x90A20000
[   11.491930] [drm] register mmio size: 65536
[   11.493649] [drm] Detected VRAM RAM=256M, BAR=256M
[   11.493650] [drm] RAM width 128bits DDR
[   11.493745] [drm] radeon: 256M of VRAM memory ready
[   11.493746] [drm] radeon: 512M of GTT memory ready.
[   11.493817] [drm] radeon: irq initialized.
[   11.493820] [drm] GART: num cpu pages 131072, num gpu pages 131072
[   11.494334] [drm] Loading RV630 Microcode
[   11.644264] [drm] ring test succeeded in 1 usecs
[   11.644404] [drm] radeon: ib pool ready.
[   11.644465] [drm] ib test succeeded in 0 usecs
[   11.644468] [drm] Enabling audio support
[   11.644951] [drm] Radeon Display Connectors
[   11.644952] [drm] Connector 0:
[   11.644954] [drm]   DVI-I
[   11.644955] [drm]   DDC: no ddc bus - possible BIOS bug - please
report to xorg-driver-ati at lists.x.org
[   11.644956] [drm]   Encoders:
[   11.644957] [drm]     CRT2: INTERNAL_KLDSCP_DAC2
[   11.644959] [drm]     TV1: INTERNAL_KLDSCP_DAC2
[   11.644960] [drm]     DFP1: INTERNAL_KLDSCP_TMDS1
[   11.644961] [drm] Connector 1:
[   11.644962] [drm]   DVI-I
[   11.644963] [drm]   HPD2
[   11.644965] [drm]   DDC: 0x7e40 0x7e40 0x7e44 0x7e44 0x7e48 0x7e48
0x7e4c 0x7e4c
[   11.644966] [drm]   Encoders:
[   11.644968] [drm]     CRT1: INTERNAL_KLDSCP_DAC1
[   11.644969] [drm]     DFP2: INTERNAL_LVTM1
[   11.696891] [drm] Internal thermal controller with fan control
[   11.696947] [drm] radeon: power management initialized
[   11.807426] [drm] fb mappable at 0x80141000
[   11.807427] [drm] vram apper at 0x80000000
[   11.807429] [drm] size 5242880
[   11.807430] [drm] fb depth is 24
[   11.807431] [drm]    pitch is 5120
[   12.225159] fb0: radeondrmfb frame buffer device
[   12.225160] drm: registered panic notifier
[   12.225172] [drm] Initialized radeon 2.6.0 20080528 for
0000:02:00.0 on minor 0


$ cat /etc/X11/xorg.conf
Section "Module"
	Load  "glx"
EndSection

Section "Monitor"
	Identifier   "vga2"
	Option	    "DPMS" "true"
	Option      "LeftOf" "vga1"
	Option      "Enable" "true"
EndSection

Section "Monitor"
	Identifier  "vga1"
	Option	    "DPMS" "true"
EndSection

Section "Device"
	Identifier  "Radeon HD 2600 XT"
	Driver      "radeon"
	BusID       "PCI:2:0:0"
	Option	    "monitor-VGA1" "vga1"
	Option      "monitor-VGA2" "vga2"
EndSection

Section "Screen"
	Identifier "Default Screen"
	Device     "Default Device"
	Monitor    "vga1"
	DefaultDepth     24
	SubSection "Display"
	Virtual   2560 1024
	EndSubSection
EndSection

$ uname -a
Linux username-MacPro 2.6.36-020636-generic #201010210905 SMP Thu Oct
21 10:17:53 UTC 2010 i686 GNU/Linux
<by some reason, i replaced username with "username">

$ lspci | grep VGA
02:00.0 VGA compatible controller: ATI Technologies Inc RV630 [Radeon HD 2600XT]

$ xrandr -q
Screen 0: minimum 320 x 200, current 1280 x 1024, maximum 8192 x 8192
DVI-0 disconnected (normal left inverted right x axis y axis)
DVI-1 connected 1280x1024+0+0 (normal left inverted right x axis y
axis) 338mm x 270mm
   1280x1024      60.0*+   75.0
   1280x960       60.0
   1152x864       75.0
   1024x768       75.1     70.1     60.0
   832x624        74.6
   800x600        72.2     75.0     60.3     56.2
   640x480        72.8     75.0     66.7     60.0
   720x400        70.1

-- 
Haruka YAGNI
hyagni at gmail.com