+ 1 for this bug from another RS880 / G785 IGP user: Using Jessie with 3.16.4 amd64 kernel I get random blank screens for 2 seconds with an 1080p ACER LCD connected to the DVI or HDMI input (monitor supports both inputs, as does my AsRock mainboard)
Kernel 3.14 in Jessie was not affected by this bug, but a quick google dug up several blasts from the past in Squeeze/Wheezy during the grub2/KMS migration phase: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=529178 http://lists.opensuse.org/opensuse-bugs/2014-09/msg00789.html 3.16 related bugs of that kind can be found in Opensuse 13.2 as well - I will report on that to the Novell guys later. https://bugzilla.novell.com/show_bug.cgi?id=767360 Thus people migrating from a flawless working Ubuntu 12.04 (kernel 3.14) to 12.10 (kernel 3.16) are apparently hit by this as well: http://ubuntuforums.org/archive/index.php/t-2246456.html As always: the bug will not show when disabling KMS with the "nomodeset" boot parameter, which leaves us with a totally messed up aspect ratio caused by an unfitting vesa mode resolution. If you're affected by the bug it will most likely be trigged by scrolling in a webbrowser (pick a loaded site for testing this) , but I also came along the bug by the page-up action in an x-terminal. Another observation that might explain the difficulty to track this down in the past: it's gpu type and monitor type dependend: The same Acer monitor will *not* show the bug on *the same* installation, if it's a run on an SB 850 chipset - that one is only slightly newer to my understanding: (RS880P , IGP version would be called an ATI Radeon HD 4290 and still be an UVD-2 type) And a G780 chipset (RS780) connected to HDMI and a Phillips monitor using the same Jessie installation does *not* trigger the bug ... so indeed, this might be tricky to reproduce. Here's one more non-blanking related thing I noticed about the radeon KMS framebuffer: It seems to ignore the gxfpayload grub parameter: You can successfully set a high grub2 resolution with gfxmode=auto and verify this with vbeinfo in the grub2 command line, but when you start booting you will end up using "gxfpayload_linux=text" in the initial booting phase, then switch to a higher resolution, then switch one last time to the X resolution (and well ... by then the blank screen bug will continue to kick in eventually and intermittently) Forcing grub_gfxpayload_linux="keep" in /etc/default/grub does not seem to help, that value is ignored. You will end up with the 80-lines character mode then, should you try to use a cryptoroot hook and type in the luks pw in that early booting stage. Hope this helps to fix this bug for good, I volunteer for more testings on several radeonhd gpus + monitors Regards TuxoHolic
