Testing drm-i915-update-38 (c6d9af5) with patched i915_gem.c, encouraging results.

[Arto Pekkanen]

Okay.

Anyway, I just found out that after 12 hours uptime the system dropped 
HDMI3, and now does not allow me to enable/configure HDMI3. I can only 
use LVDS and HDMI2.

If I try to re-enable HDMI3 then X.org crashes and I get the following 
dmesg:
error: [drm:pid974:intel_crtc_set_config] *ERROR* failed to set mode on 
[CRTC:7]
pid 974 (Xorg), uid 0: exited on signal 6 (core dumped)

So it seems like the multiple display support is not yet stable.

In FreeBSD 10.2 enabling a third output instantly crashes X.org, with 
this new driver I can enable third output after reboot, but the output 
will drop sooner or later.

Alexander Mishurov kirjoitti 08.02.2016 07:51:
> This is a bug actually, seems to be related to some kind of race 
> condition.
> Original Intel driver from Linux even in later versions uses BUG_ON
> for this expression.
> 
> On 08/02/16 06:09, Arto Pekkanen wrote:
>> Hi again.
>> 
>> I realized that previously the  drm-i915-update-38 (c6d9af5) kernel 
>> crashed because of a BUG_ON trap in i915_gem.c, not because of actual 
>> code fault.
>> 
>> Then I found the following discussion in GitHub: 
>> https://github.com/freebsd/freebsd-base-graphics/issues/2
>> 
>> There the user myfreeweb "McGyver'd" the BUG_ON trap away by replacing 
>> it with WARN_ON -macro. I wanted to see if the driver would work, so I 
>> did the same.
>> 
>> Attached is the diff that replaces BUG_ON with WARN_ON in i915_gem.c 
>> and thus makes the kernel not crash while playing games/openarena.
>> 
>> The results:
>> - kernel boots
>> - vt console works
>> - LVDS + 2 monitors on HDMI2 and HDMI3, all work with native 
>> resolutions,
>>   NOTE: this is an IMPROVEMENT! Previously X.org would HANG if I 
>> enabled more than 2 monitors!
>> - video playback is perfect, no tearing, minimal CPU use, tested with
>>   - www/chromium
>>   - multimedia/mpv (with VAAPI enabled in multimedia/mpv and 
>> multimedia/ffmpeg)
>> - games/openarena works just fine
>> 
>> In fact, I can actually run games/openarena at the same time with 
>> www/chromium wathing https://www.youtube.com/watch?v=5xkNy9gfKOg (full 
>> HD tearing test video), with some stuttering on both ... but this is 
>> to be expected, because the kernel has to serve 2 OpenGL pipes at the 
>> same time which is problematic.
>> 
>> And because I can now use 3 outputs at the same time, I am very 
>> impressed.
>> 
>> I see many warnings like this in dmesg:
>> Feb  8 04:33:15 leno kernel: error: 
>> [drm:pid1073:i915_gem_object_move_to_inactive] *ERROR* WARN ON: 
>> obj->base.write_domain & ~I915_GEM_GPU_DOMAINS
>> 
>> The frequency between these errors is about one second when I run 
>> games/openarena. With www/chromium I do not see these warnings.
>> 
>> The only real gripe I have is that the FreeBSD 11 -based kernel does 
>> not detect my Intel Wifi chip, yet stock FreeBSD 10.2 was able to do 
>> that. Should I report this as a regression somewhere? The problem with 
>> reporting this is that I am running FreeBSD 10.2 userland, and I feel 
>> like the developers might not want to deal with that.
>> 
>> I will leave the laptop on while I sleep, leave it running the Tearing 
>> Test -video mentioned above. If it crashes I will post core dump etc.
>> 
> 
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-- 
Arto Pekkanen