It appears I was confused and most recent testing _did_ happen in the same session post-reboot, see timestamps in log snippet below;
The bug recurs after the display goes to DPMS standby/sleep. It also appears the "display corruption on switching modes" occurs after the display has its first (or multiple) chances to sleep as I hit it now flipping to 1280x720 the second time in the session - no more clear 1280x720, again a wait for a garbled screen to revert. While Xorg log shows the machine rereading DDC/EDID data when things are woken out of DPMS (and the seizure-inducing flicker recommences), xrandr shows _no_ difference in modelines before/after... not really a surprise but was worth confirming. [I should probably be hunting this bug upstream where it's probably already fixed; maybe another night.] [ 718.155] (II) RADEON(0): Allocate new frame buffer 1280x720 stride 1280 [ 718.155] (II) RADEON(0): VRAM usage limit set to 48193K [ 748.647] (II) RADEON(0): Allocate new frame buffer 1920x1088 stride 1920 [ 748.692] (II) RADEON(0): VRAM usage limit set to 44089K [ 1528.849] (II) RADEON(0): EDID vendor "HWP", prod id 12294 [ 1528.849] (II) RADEON(0): Using hsync ranges from config file [ 1528.849] (II) RADEON(0): Using vrefresh ranges from config file [ 1528.849] (II) RADEON(0): Printing DDC gathered Modelines: ... [ 27408.170] (II) RADEON(0): Allocate new frame buffer 1280x720 stride 1280 [ 27408.171] (II) RADEON(0): VRAM usage limit set to 48193K [ 27415.531] (II) RADEON(0): Allocate new frame buffer 1920x1088 stride 1920 [ 27415.576] (II) RADEON(0): VRAM usage limit set to 44089K [ 30534.725] (II) RADEON(0): EDID vendor "HWP", prod id 12294 [ 30534.734] (II) RADEON(0): Using hsync ranges from config file [ 30534.734] (II) RADEON(0): Using vrefresh ranges from config file [ 30534.734] (II) RADEON(0): Printing DDC gathered Modelines: [ 30534.734] (II) RADEON(0): Modeline "1920x1080"x0.0 148.50 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync (67.5 kHz eP) [ 30534.734] (II) RADEON(0): Modeline "800x600"x0.0 40.00 800 840 968 1056 600 601 605 628 +hsync +vsync (37.9 kHz e) [ 30534.734] (II) RADEON(0): Modeline "640x480"x0.0 25.18 640 656 752 800 480 490 492 525 -hsync -vsync (31.5 kHz e) [ 30534.734] (II) RADEON(0): Modeline "720x400"x0.0 28.32 720 738 846 900 400 412 414 449 -hsync +vsync (31.5 kHz e) [ 30534.734] (II) RADEON(0): Modeline "1024x768"x0.0 65.00 1024 1048 1184 1344 768 771 777 806 -hsync -vsync (48.4 kHz e) [ 30534.734] (II) RADEON(0): Modeline "1280x720"x60.0 74.48 1280 1336 1472 1664 720 721 724 746 -hsync +vsync (44.8 kHz e) [ 30534.734] (II) RADEON(0): Modeline "1280x1024"x0.0 108.00 1280 1328 1440 1688 1024 1025 1028 1066 +hsync +vsync (64.0 kHz e) [ 30534.734] (II) RADEON(0): Modeline "1440x900"x0.0 106.50 1440 1520 1672 1904 900 903 909 934 -hsync +vsync (55.9 kHz e) [ 30534.735] (II) RADEON(0): Modeline "1680x1050"x0.0 146.25 1680 1784 1960 2240 1050 1053 1059 1089 -hsync +vsync (65.3 kHz e) [ 30534.735] (II) RADEON(0): Modeline "1920x1080"x60.0 172.80 1920 2040 2248 2576 1080 1081 1084 1118 -hsync +vsync (67.1 kHz e) === While flickering: --- xrandr -q --verbose Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 4096 x 4096 VGA-0 connected 1920x1080+0+0 (0x53) normal (normal left inverted right x axis y axis) 510mm x 287mm Identifier: 0x51 Timestamp: 27407961 Subpixel: no subpixels Gamma: 1.0:1.0:1.0 Brightness: 1.0 Clones: CRTC: 0 CRTCs: 0 1 Transform: 1.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 1.000000 filter: EDID: 00ffffffffffff0022f0063001010101 1216010368331d782e77c5a3544f9f27 115054a1080081c081809500b300d1c0 010101010101023a801871382d40582c 4500fe1f1100001e000000fd00324c18 5e14000a202020202020000000fc0048 50204c56323331310a202020000000ff 0036434d323138305a43510a2020004c load detection: 1 (0x00000001) range: (0,1) 1920x1080 (0x53) 148.5MHz +HSync +VSync *current +preferred h: width 1920 start 2008 end 2052 total 2200 skew 0 clock 67.5KHz v: height 1080 start 1084 end 1089 total 1125 clock 60.0Hz 1680x1050 (0x54) 146.2MHz -HSync +VSync h: width 1680 start 1784 end 1960 total 2240 skew 0 clock 65.3KHz v: height 1050 start 1053 end 1059 total 1089 clock 60.0Hz 1280x1024 (0x55) 108.0MHz +HSync +VSync h: width 1280 start 1328 end 1440 total 1688 skew 0 clock 64.0KHz v: height 1024 start 1025 end 1028 total 1066 clock 60.0Hz 1440x900 (0x56) 106.5MHz -HSync +VSync h: width 1440 start 1520 end 1672 total 1904 skew 0 clock 55.9KHz v: height 900 start 903 end 909 total 934 clock 59.9Hz 1280x720 (0x57) 74.4MHz -HSync +VSync h: width 1280 start 1336 end 1472 total 1664 skew 0 clock 44.7KHz v: height 720 start 721 end 724 total 746 clock 60.0Hz 1024x768 (0x58) 65.0MHz -HSync -VSync h: width 1024 start 1048 end 1184 total 1344 skew 0 clock 48.4KHz v: height 768 start 771 end 777 total 806 clock 60.0Hz 800x600 (0x59) 40.0MHz +HSync +VSync h: width 800 start 840 end 968 total 1056 skew 0 clock 37.9KHz v: height 600 start 601 end 605 total 628 clock 60.3Hz 640x480 (0x5a) 25.2MHz -HSync -VSync h: width 640 start 656 end 752 total 800 skew 0 clock 31.5KHz v: height 480 start 490 end 492 total 525 clock 60.0Hz 720x400 (0x5b) 28.3MHz -HSync +VSync h: width 720 start 738 end 846 total 900 skew 0 clock 31.5KHz v: height 400 start 412 end 414 total 449 clock 70.1Hz === Immediately after modeflip via Displays 'workaround' - diff shows no change except timestamp: --- xrandr -q --verbose Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 4096 x 4096 VGA-0 connected 1920x1080+0+0 (0x53) normal (normal left inverted right x axis y axis) 510mm x 287mm Identifier: 0x51 Timestamp: 31879702 Subpixel: no subpixels Gamma: 1.0:1.0:1.0 Brightness: 1.0 Clones: CRTC: 0 CRTCs: 0 1 Transform: 1.000000 0.000000 0.000000 0.000000 1.000000 0.000000 0.000000 0.000000 1.000000 filter: EDID: 00ffffffffffff0022f0063001010101 1216010368331d782e77c5a3544f9f27 115054a1080081c081809500b300d1c0 010101010101023a801871382d40582c 4500fe1f1100001e000000fd00324c18 5e14000a202020202020000000fc0048 50204c56323331310a202020000000ff 0036434d323138305a43510a2020004c load detection: 1 (0x00000001) range: (0,1) 1920x1080 (0x53) 148.5MHz +HSync +VSync *current +preferred h: width 1920 start 2008 end 2052 total 2200 skew 0 clock 67.5KHz v: height 1080 start 1084 end 1089 total 1125 clock 60.0Hz 1680x1050 (0x54) 146.2MHz -HSync +VSync h: width 1680 start 1784 end 1960 total 2240 skew 0 clock 65.3KHz v: height 1050 start 1053 end 1059 total 1089 clock 60.0Hz 1280x1024 (0x55) 108.0MHz +HSync +VSync h: width 1280 start 1328 end 1440 total 1688 skew 0 clock 64.0KHz v: height 1024 start 1025 end 1028 total 1066 clock 60.0Hz 1440x900 (0x56) 106.5MHz -HSync +VSync h: width 1440 start 1520 end 1672 total 1904 skew 0 clock 55.9KHz v: height 900 start 903 end 909 total 934 clock 59.9Hz 1280x720 (0x57) 74.4MHz -HSync +VSync h: width 1280 start 1336 end 1472 total 1664 skew 0 clock 44.7KHz v: height 720 start 721 end 724 total 746 clock 60.0Hz 1024x768 (0x58) 65.0MHz -HSync -VSync h: width 1024 start 1048 end 1184 total 1344 skew 0 clock 48.4KHz v: height 768 start 771 end 777 total 806 clock 60.0Hz 800x600 (0x59) 40.0MHz +HSync +VSync h: width 800 start 840 end 968 total 1056 skew 0 clock 37.9KHz v: height 600 start 601 end 605 total 628 clock 60.3Hz 640x480 (0x5a) 25.2MHz -HSync -VSync h: width 640 start 656 end 752 total 800 skew 0 clock 31.5KHz v: height 480 start 490 end 492 total 525 clock 60.0Hz 720x400 (0x5b) 28.3MHz -HSync +VSync h: width 720 start 738 end 846 total 900 skew 0 clock 31.5KHz v: height 400 start 412 end 414 total 449 clock 70.1Hz -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xserver-xorg-video-ati in Ubuntu. https://bugs.launchpad.net/bugs/1181355 Title: R300 (RS480): Intermittent flickering corruption top half of display (VGA, 1080p) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xserver-xorg-video-ati/+bug/1181355/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : ubuntu-x-swat@lists.launchpad.net Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp