Dual monitor excessive warnings

[Bruce_D_]

System Setup Information:
-----------------------------------------

System Used: Gigabyte GA-Z170-HD3P
CPU SKU: Intel(R) Core(TM) i5-6500 CPU @ 3.20GHz
GPU SKU: integrated
Processor Line: ?
System BIOS Version: BIOS F2 07/27/2015
CMOS settings: default
Graphics Driver Version:
GOP/VBIOS Version: ?
Operating System: Linux
OS Version: 4.3.3
API:
Occurs on non-Intel GPUs?: NA

I have two monitors hooked up to the motherboard, one DVI-D and the other HDMI.

The software I'm using is:

linux-4.3.3 with firmware skl_dmc_ver1.bin compiled into the kernel image.
xf86-video-intel-0340718 Intel Driver
libva-1.6.2
libva-intel-driver-1.6.2
libvdpau-1.1.1
libvdpau-va-gl-0.3.4

libdrm-2.4.66
Mesa-11.0.8

The window manager is xfce-4.12

Visually everything works, however every time I move the cursor from one monitor to the other, I get in my logs:

WARNING: CPU: 0 PID: 782 at drivers/gpu/drm/i915/intel_pm.c:3668 skl_update_other_pipe_wm+0x1b5/0x1c0()
WARN_ON(!wm_changed)
Modules linked in:
 uvcvideo videobuf2_vmalloc videobuf2_memops videobuf2_core
CPU: 0 PID: 782 Comm: Xorg Tainted: G        W       4.3.3-lfs-SVN-20160104 #1
Hardware name: Gigabyte Technology Co., Ltd. To be filled by O.E.M./Z170-HD3P-CF, BIOS F2 07/27/2015
 ffffffff81b195f8 ffff880265e43658 ffffffff8142be9f ffff880265e436a0
 ffff880265e43690 ffffffff8108de88 ffff880267f81000 ffff880265e437dc
 ffff880267f80000 0000000000000000 ffff880265e43728 ffff880265e436f0
Call Trace:
 [<ffffffff8142be9f>] dump_stack+0x44/0x55
 [<ffffffff8108de88>] warn_slowpath_common+0x78/0xb0
 [<ffffffff8108df07>] warn_slowpath_fmt+0x47/0x50
 [<ffffffff81553805>] skl_update_other_pipe_wm+0x1b5/0x1c0
 [<ffffffff815539a6>] skl_update_wm+0x196/0x6a0
 [<ffffffff8158fd40>] ? gen9_read32+0xf0/0x270
 [<ffffffff81557e69>] intel_update_watermarks+0x19/0x20
 [<ffffffff815ab1e1>] intel_atomic_commit+0x3f1/0x1340
 [<ffffffff8153fad0>] ? drm_atomic_check_only+0x210/0x540
 [<ffffffff8153eefd>] ? drm_atomic_get_crtc_state+0x2d/0xd0
 [<ffffffff8153fe32>] drm_atomic_commit+0x32/0x50
 [<ffffffff8151c1ea>] drm_atomic_helper_disable_plane+0xea/0x130
 [<ffffffff815307e5>] __setplane_internal+0x235/0x2f0
 [<ffffffff815309b6>] drm_mode_cursor_universal+0x116/0x1f0
 [<ffffffff81530b0c>] drm_mode_cursor_common+0x7c/0x180
 [<ffffffff81185901>] ? set_fd_set+0x21/0x30
 [<ffffffff8153478c>] drm_mode_cursor_ioctl+0x3c/0x40
 [<ffffffff81526324>] drm_ioctl+0x124/0x4d0
 [<ffffffff81534750>] ? drm_mode_setcrtc+0x4c0/0x4c0
 [<ffffffff8118860c>] ? dput+0x9c/0x1f0
 [<ffffffff81172893>] ? __vfs_read+0x23/0xd0
 [<ffffffff81184e00>] do_vfs_ioctl+0x280/0x460
 [<ffffffff81097365>] ? recalc_sigpending+0x15/0x50
 [<ffffffff8109807d>] ? __set_task_blocked+0x2d/0x70
 [<ffffffff81185054>] SyS_ioctl+0x74/0x80
 [<ffffffff818fc197>] entry_SYSCALL_64_fastpath+0x12/0x6a
---[ end trace 1fefbff8a5313d63 ]---

I emphasize here that there is no visual problem--only a very full kernel ring buffer and a large/growing log file.

Since the message references drivers/gpu/drm/i915/intel_pm.c, I looked at that and saw:

/*
 * If we end up re-computing the other pipe WM values, it's
 * because it was really needed, so we expect the WM values to
 * be different.
 */
 WARN_ON(!wm_changed);

So I commented out the WARN_ON line and the messages went away.

I also experimented with the 4.4 kernel, but there is a much bigger problem there.  The DVI-D connected monitor does not seem to be recognized and video output only goes to the HDMI connected monitor.

If you need additional info, I'll be clad to run tests or provide logs.

[Michael_C_Intel2]

Hi Bruce,

For Linux and our MESA driver questions and issues your best options are:

• File a bug in Mesa's public bug tracker: https://bugs.freedesktop.org/enter_bug.cgi?product=Mesa . In the component field, select Drivers/DRI./i965.
• Send a message to Mesa's development mailing list http://lists.freedesktop.org/mailman/listinfo/mesa-dev .
• Most of the Intel Mesa developers are on IRC in irc://irc.freenode.net/#intel-gfx or irc://irc.freenode.net/#dri-devel. People there are very helpful.

I suggest that you open a Bugzilla ticket with the information in this post. The team will probably then ask you a lot of clarifying questions (OS? gpu pci id? Mesa version? etc etc).

Also, it's often helpful to directly contact the owner of the Mesa package for your Linux distribution. Sometimes the package owner is very familiar with frequent bugs that are specific to that distribution. On RPM based distros, such as Fedora, you can find the packager by examining the package's changelog with this command: `rpm -q --changelog mesa-libGL`. On Debian based distros, such as Ubuntu, I think the apt-cache command gives you the needed info.

For LVDS issues, your best option is to contact one of Intel's kernel graphics developers. You can find them on IRC at irc://irc.freenode.net/#intel-gfx and on the mailing list  http://lists.freedesktop.org/mailman/listinfo/intel-gfx . (I would help, but I'm not a kernel developer and LVDS is outside my domain).

-Michael