On Wed, 2016-08-31 at 21:51 +0000, Zanoni, Paulo R wrote:
Hi
Em Qua, 2016-08-31 às 14:43 -0700, James Bottomley escreveu:
On Wed, 2016-08-31 at 11:23 -0700, James Bottomley wrote:
On Fri, 2016-08-26 at 09:10 -0400, James Bottomley wrote:
We seem to have an xrandr regression with skylake now. What's happening is that I can get output on to a projector, but the system is losing video when I change the xrandr sessions (like going from a --above b to a --same-as b). The main screen goes blank, which is basically a reboot situation. Unfortunately, I can't seem to get the logs out of systemd to see if there was a dump to dmesg (the system was definitely responding).
I fell back to 4.6.2 which worked perfectly, so this is definitely some sort of regression. I'll be able to debug more fully when I get back home from the Linux Security Summit.
I'm home now. Unfortunately, my monitor isn't as problematic as the projector, but by flipping between various modes and separating and overlaying the panels with --above and --same-as (xrandr), I can eventually get it to the point where the main LCD panel goes black and can only be restarted by specifying a different mode.
This seems to be associated with these lines in the X
[ 14714.389] (EE) intel(0): failed to set mode: Invalid argument [22]
But the curious thing is that even if this fails with the error message once, it may succeed a second time, so it looks to be a transient error translation problem from the kernel driver.
I've attached the full log below.
This is only with a VGA output. I currently don't have a HDMI dongle, but I'm in the process of acquiring one.
After more playing around, I'm getting thousands of these in the kernel log (possibly millions: the log wraps very fast):
[23504.873606] [drm:intel_dp_start_link_train [i915]] *ERROR* failed to train DP, aborting
And then finally it gives up with
[25023.770951] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe B FIFO underrun [25561.926075] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe A FIFO underrun
And the crtc for the VGA output becomes non-responsive to any configuration command. This requires a reboot and sometimes a UEFI variable reset before it comes back.
Please see this discussion: https://patchwork.freedesktop.org/patch/103237/
Do you have this patch on your tree? Does the problem go away if you revert it?
Yes, I've got it, it went in in 4.8-rc3 according to git:
commit 58e311b09c319183254d9220c50a533e7157c9ab Author: Matt Roper matthew.d.roper@intel.com Date: Thu Aug 4 14:08:00 2016 -0700
drm/i915/gen9: Give one extra block per line for SKL plane WM calculations
Reverting it causes the secondary display not to sync pretty much at all. However, in the flickers I can see, it does work OK and doesn't now crash switching from --same-as to --above and back
I also still get the logs filling up with the link training errors.
On balance, although the behaviour is different, it's not an improvement because if I can't sync with the projector, I can't really use this as a fix.
James