Created attachment 129021 [details] Archive of files containing configuration and log information (see description for details). [i915][SNB] This issue is occurring after a restart while the LightDM logon screen is displayed prior to any attempt to actually logon. I am seeing the display blink intermittently (i.e. the display momentarily goes blank and then returns). In my experience this issue is repeatable. The time interval between blinks is variable. The display continues to blink even after logon. In order to reproduce this issue I am using the following configuration: - Ubuntu 16.04.1 installed from ISO image (no updates applied from the Ubuntu repository). - TV display connected via HDMI connection (no other displays connected). This issue occurs with the v4.4 Linux kernel from the DVD image. In an attempt to further investigate this issue I have experimented with other Linux kernels from http://kernel.ubuntu.com/~kernel-ppa/mainline/. The issue still exists with Linux kernel v4.9.4. With this kernel the display blinks several times (say 10) within a couple of minutes of a restart. I have gathered some configuration and log information which I hope will help you understand the issue and hopefully suggest a fix/workaround. In addition I have tried older Linux kernels and in my experience the most recent kernel that does NOT exhibit this issue is v4.2.8-ckt13. I have gathered some configuration and log information when testing with this kernel as well. I am attaching two sets of files containing configuration and log information when testing with v4.9.4 (display issue exists) and v4.2.8-ckt13 (display issue does NOT exist). The names of these attachments are prefixed with the relevant Linux kernel version. The information gathered covers: - dmesg output with drm.debug=0xe. - dmidecode output for hardware information. - an Intel Register Dump. - uname output. - a VBIOS dump. - xrandr output. I am currently using the same hardware with a Windows based Media Centre and am having no display issues, from this I am concluding that I do not have an underlying hardware related issue. I am aiming to replace Windows with Linux and this is how I have discovered this display blinking issue. Please let me know if further information is required. I am keen to help but I am new to Linux so may need more detailed instructions than experienced contributors.
(In reply to synup from comment #0) > Created attachment 129021 [details] > Archive of files containing configuration and log information (see > description for details). Hello, Sorry for the delay. This seems to be a regression, is this problem still present on the latest kernel? Are your HW and SW settings still the same? Thank you.
Using exactly the same hardware and software I have followed the instructions I outlined in my first report except that I have retested using the latest kernel, namely v4.12.1 from http://kernel.ubuntu.com/~kernel-ppa/mainline/. Unfortunately, I can report that the issue still exists and the behaviour is the same as my first report. I hope this information helps you to make some progress with this.
(In reply to synup from comment #2) > Using exactly the same hardware and software I have followed the > instructions I outlined in my first report except that I have retested using > the latest kernel, namely v4.12.1 from > http://kernel.ubuntu.com/~kernel-ppa/mainline/. > > Unfortunately, I can report that the issue still exists and the behaviour is > the same as my first report. > > I hope this information helps you to make some progress with this. Hello again, Thanks for the answer. Could you please attach new dmesg with kernel 4.12? Is your display HD, 4K, etc? Once provided the information please mark as REOPEN. Thanks.
Created attachment 132767 [details] Archive of dmesg with kernel 4.12 As requested, I have attached a new dmesg with kernel 4.12 (dmesg1.log). My display is a Sony HD TV 1920x1080 @ 50Hz. I hope this information helps you to make some progress with this. Thanks.
(In reply to synup from comment #4) Thank you for the information, If any other log is needed for this case it would be commented below.
Hello Synup, Is there any chance that you could do a bisection of the issue?
Hi Elizabeth, When I raised this issue I mentioned that I had experimented with other Linux kernels from http://kernel.ubuntu.com/~kernel-ppa/mainline/. Specifically the most recent kernel that does NOT exhibit this issue was v4.2.8-ckt13. The issue exists in kernel v4.4 from the 16.04.1 DVD image and all the later kernels that I have tried with the latest being v4.12. I guess this is not what you mean by 'a bisection of the issue' so I am afraid that I don't understand what you are asking for. I am willing do some more investigation for you, but as I am still relatively new to Linux please can you provide me with some more detailed instructions? Thanks.
Hello Synup, You can find information about it in the internet like in this page: http://www.marclittlemore.com/how-to-find-bugs-using-git-bisect-with-this-easy-guide/ or this one: https://www.metaltoad.com/blog/beginners-guide-git-bisect-process-elimination Between 4.2.8 to 4.4 there is a big gap so is really hard to point where the issue started. You'll need to reduce the options to find the culprit. Hope this helps.
First of all. Sorry about spam. This is mass update for our bugs. Sorry if you feel this annoying but with this trying to understand if bug still valid or not. If bug investigation still in progress, please ignore this and I apologize! If you think this is not anymore valid, please comment to the bug that can be closed. If you haven't tested with our latest pre-upstream tree(drm-tip), can you do that also to see if issue is valid there still and if you cannot see issue there, please comment to the bug.
Closing, please re-open if still occurs.
Use of freedesktop.org services, including Bugzilla, is subject to our Code of Conduct. How we collect and use information is described in our Privacy Policy.