Bug 1669

Summary:	default mode order prevails over the recommended mode on LCD
Product:	xorg	Reporter:	Alexei Podtelezhnikov <apodtele>
Component:	Server/General	Assignee:	Xorg Project Team <xorg-team>
Status:	RESOLVED INVALID	QA Contact:
Severity:	normal
Priority:	high	CC:	erik.andren
Version:	6.7.0
Hardware:	x86 (IA32)
OS:	Linux (All)
Whiteboard:
i915 platform:		i915 features:

Description Alexei Podtelezhnikov 2004-10-18 21:50:37 UTC

Xorg probes and assigns display modes from the highest refresh rate to the 
lowest for a given resolution. Hence, the highest allowed refresh rate is 
chosen as the default. This was historically right and sound for CRT monitors. 
This is a wrong assumption for LCDs. My display, Dell 1703FP, actually prefers 
a lower 1280x1024@60Hz mode instead of the allowed 1280x1026@75Hz. The bug is 
that my display actually _REPORTS_ the preferable rate, while Xorg ignores it. 
 
Here is the relevant parts of the log file: 
 
(II) R128(0): VESA VBE DDC supported 
(II) R128(0): VESA VBE DDC Level 2 
(II) R128(0): VESA VBE DDC transfer in appr. 2 sec. 
(II) R128(0): VESA VBE DDC read successfully 
(II) R128(0): Manufacturer: DEL  Model: 3010  Serial#: 1095191382 
(II) R128(0): Year: 2004  Week: 35 
(II) R128(0): EDID Version: 1.3 
(II) R128(0): Analog Display Input,  Input Voltage Level: 0.700/0.300 V 
(II) R128(0): Sync:  Separate  Composite  SyncOnGreen 
(II) R128(0): Max H-Image Size [cm]: horiz.: 34  vert.: 27 
(II) R128(0): Gamma: 2.20 
(II) R128(0): DPMS capabilities: StandBy Suspend Off; RGB/Color Display 
(II) R128(0): Default color space is primary color space 
(II) R128(0): First detailed timing is preferred mode 
............... 
(II) R128(0): Supported additional Video Mode: 
(II) R128(0): clock: 108.0 MHz   Image Size:  338 x 270 mm 
(II) R128(0): h_active: 1280  h_sync: 1328  h_sync_end 1440 h_blank_end 1688 
h_border: 0 
(II) R128(0): v_active: 1024  v_sync: 1025  v_sync_end 1028 v_blanking: 1066 
v_border: 0 
............... 
(--) R128(0): Virtual size is 1280x1024 (pitch 1280) 
(**) R128(0): *Default mode "1280x1024": 135.0 MHz, 80.0 kHz, 75.0 Hz 
(II) R128(0): Modeline "1280x1024"  135.00  1280 1296 1440 1688  1024 1025 
10281066 +hsync +vsync 
............... 
(**) R128(0):  Default mode "1280x1024": 108.0 MHz, 64.0 kHz, 60.0 Hz 
(II) R128(0): Modeline "1280x1024"  108.00  1280 1328 1440 1688  1024 1025 
10281066 +hsync +vsync 
 
I was able to override the default mode order by custom ModeLine. I wish X.org 
respected the prefered mode in the firstplace when the monitor is plugedin. For 
example, read-edid-1.4.1 gets it right.

Comment 1 Alex Deucher 2004-10-21 06:19:24 UTC

Does your monitor also announce support for 1280x1024@75hz via DDC? if so,
that's the problem.  the driver picks the mode based on the best refresh rate
available.

Comment 2 Alexei Podtelezhnikov 2004-10-21 07:41:37 UTC

It seems to me that, despite 1280x1024@75Hz is supported and announced, the 
monitor clearly states that it prefers 1280x1024@60Hz. 
 
(II) Loading sub module "ddc" 
(II) LoadModule: "ddc" 
(II) Reloading /usr/X11R6/lib/modules/libddc.a 
(II) R128(0): VESA VBE DDC supported 
(II) R128(0): VESA VBE DDC Level 2 
(II) R128(0): VESA VBE DDC transfer in appr. 2 sec. 
(II) R128(0): VESA VBE DDC read successfully 
(II) R128(0): Manufacturer: DEL  Model: 3010  Serial#: 1095191382 
(II) R128(0): Year: 2004  Week: 35 
(II) R128(0): EDID Version: 1.3 
(II) R128(0): Analog Display Input,  Input Voltage Level: 0.700/0.300 V 
(II) R128(0): Sync:  Separate  Composite  SyncOnGreen 
(II) R128(0): Max H-Image Size [cm]: horiz.: 34  vert.: 27 
(II) R128(0): Gamma: 2.20 
(II) R128(0): DPMS capabilities: StandBy Suspend Off; RGB/Color Display 
(II) R128(0): Default color space is primary color space 
(II) R128(0): First detailed timing is preferred mode 
(II) R128(0): redX: 0.640 redY: 0.330   greenX: 0.300 greenY: 0.600 
(II) R128(0): blueX: 0.150 blueY: 0.060   whiteX: 0.312 whiteY: 0.329 
(II) R128(0): Supported VESA Video Modes: 
(II) R128(0): 720x400@70Hz 
(II) R128(0): 640x480@60Hz 
(II) R128(0): 640x480@75Hz 
(II) R128(0): 800x600@60Hz 
(II) R128(0): 800x600@75Hz 
(II) R128(0): 1024x768@60Hz 
(II) R128(0): 1024x768@75Hz 
(II) R128(0): 1280x1024@75Hz 
(II) R128(0): Manufacturer's mask: 0 
(II) R128(0): Supported Future Video Modes: 
(II) R128(0): #0: hsize: 1280  vsize 1024  refresh: 60  vid: 32897 
(II) R128(0): #1: hsize: 1152  vsize 864  refresh: 75  vid: 20337 
(II) R128(0): Supported additional Video Mode: 
(II) R128(0): clock: 108.0 MHz   Image Size:  338 x 270 mm 
(II) R128(0): h_active: 1280  h_sync: 1328  h_sync_end 1440 h_blank_end 1688 
h_border: 0 
(II) R128(0): v_active: 1024  v_sync: 1025  v_sync_end 1028 v_blanking: 1066 
v_border: 0 
(II) R128(0): Serial No: 2Y31148OAGKV 
(II) R128(0): Monitor name: DELL 1703FP 
(II) R128(0): Ranges: V min: 56  V max: 76 Hz, H min: 30  H max: 80 kHz, 
PixClock max 140 MHz 
(==) R128(0): Using gamma correction (1.0, 1.0, 1.0) 
(==) R128(0): Write-combining range (0xe0000000,0x1000000)

Comment 3 Erik Andren 2006-03-14 19:06:04 UTC

Are you still experiencing this problem with a current version of xorg?

Comment 4 Erik Andren 2006-04-16 21:34:25 UTC

I am closing this bug due to the lack of activity. Please reopen if the bug
still persists with a current version of xorg.

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