On Tue, Mar 29, 2016 at 06:44:57PM +0200, Florian Zumbiehl wrote:
Hi,
FBDEV_EMULATION vs. I915_FBDEV is probably a read herring, more likely is that for some odd reason the very first modeset fails. Once X has resurrect the screen, can you then switch to fbcon? Also please check in /sys/class/vtconsole whether the fbdev driver is loaded and bound (check the name and bind files). And make sure there's that dmesg still says it initialized the "inteldrmfb" driver.
Trying to collect that information actually solved the problem: fbcon didn't actually get loaded during boot, only the graphics drivers, which caused the screen to go blank, loading fbcon happened only when starting the X server ... seems weird to me, but I guess there is some non-obvious logic behind that, and in any case it seems to be a change in behaviour. Well, thanks for the pointer anyway, I guess! ;-)
Now, while at it: I also have a bunch of WARN_ONs and ERRORs happening (the former primarily when an Xv window disappears from the screen, it seems, the latter primarily during boot), which don't seem to have any immediate negative effects at the surface, like this:
| [ 14.815467] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe A FIFO underrun | [ 14.815642] [drm:intel_set_cpu_fifo_underrun_reporting [i915]] *ERROR* pipe B underrun | [ 14.815806] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe B FIFO underrun | [ 14.823686] [drm] initialized overlay support | [ 14.873165] [drm:intel_cpu_fifo_underrun_irq_handler [i915]] *ERROR* CPU pipe A FIFO underrun
We've fixed piles of those in recent kernels, but didn't backport all the fixes (since usually it's a silent failure, but it can correlate with black screens).
| [ 2520.457732] WARNING: CPU: 0 PID: 3193 at drivers/gpu/drm/i915/i915_gem.c:4508 i915_gem_free_object+0x277/0x280 [i915]() | [ 2520.457736] WARN_ON(obj->frontbuffer_bits)
Hm, this one should be fixed, and the patches should all be correctly marked for stable. Either there's a backlog somewhere, or we failed.
Would be great if you can test a drm-intel-nightly build (or 4.6-rc1) for either and confirm that they're gone. And for the later we really should hunt down the bugfix if it's stuck.
Also, I have occasional X server crashes (every few weeks or so) which started with 4.1.9, I think (I had 3.11.0 before that), and I had some kind of problem with Xv not working anymore until reboot with 4.1.9 which hasn't happened with 4.4.5 yet ... do you think any of those would be worth further investigation? If so, any suggestions as to how to split it all into separate issues/how to go about it?
No idea about X stuff, not my expertise ;-) -Daniel