On Mon, May 28, 2012 at 08:51:51PM +0200, Daniel Vetter wrote: > On Mon, May 28, 2012 at 1:09 AM, Linus Torvalds > <torvalds at linux-foundation.org> wrote: > > A new worry about excessively verbose i915 driver "errors" that don't > > actually seem to be errors. > > > > I got myself a micro-DP to VGA adapter so that I can use my Macbook > > Air for presentations. > > > > And testing it, hotplugging seems to work very nicely, and gone are > > the days when you had to do xrandr and crap. Things "JustWork(tm)". > > > > Goodie. > > > > Until you start looking at the dmesg log. Then it gets ugly. It's full > > of scary-looking stuff like > > > > ?------------[ cut here ]------------ > > ?WARNING: at drivers/gpu/drm/i915/intel_dp.c:350 > > intel_dp_check_edp+0x5d/0xb0() > > ?Hardware name: MacBookAir4,1 > > ?eDP powered off while attempting aux channel communication. > > ?Modules linked in: fuse rfcomm bnep nf_conntrack_netbios_ns > > nf_conntrack_broadcast .. > > ?Pid: 2126, comm: kworker/0:0 Tainted: G ? ? ? ?W ? ?3.4.0-08209-gae32adc #9 > > ?Call Trace: > > ? ?warn_slowpath_common+0x7a/0xb0 > > ? ?warn_slowpath_fmt+0x41/0x50 > > ? ?intel_dp_check_edp+0x5d/0xb0 > > ? ?intel_dp_aux_ch+0x3f/0x330 > > ? ?intel_dp_aux_native_read_retry+0xad/0x130 > > ? ?intel_dp_detect+0x240/0x2c0 > > ? ?output_poll_execute+0xba/0x1a0 > > ? ?process_one_work+0x11b/0x3c0 > > ? ?worker_thread+0x12e/0x2d0 > > ? ?kthread+0x8e/0xa0 > > ? ?kernel_thread_helper+0x4/0x10 > > ?---[ end trace 5756a4d08d9e2a83 ]--- > > > > which seems a bit extreme. I just unplugged the connector, I don't > > think it should necessarily make quite this big a deal over it. What > > does the WARN_ON() with the full call trace really buy us? > > Well, all these edp checks (I presume all the other WARN backtraces > yell around about edp, too) ensure that we have edp vdd or the panel > power on while we try to do dp aux channel communication. And because > we do need to talk to the monitor at tons of places, the backtrace is > actually really useful to debug such edp vdd confusions. > > The real problem here is that we think that the DP connector on your > MBA is connected to an edp panel, which is pretty bogus. Cc'ing Chris > and Keith who have the hw. Btw, you don't see all that dmesg spam > until you connect something real because we check the hotplug pin > status before we try to do use the dp aux channel (to get at the > edid).
Ok, Chris couldn't reproduce this on his mba. Can you please boot with drm.debug=0xe, reproduce the noise and then attach the full dmesg? Thanks, Daniel -- Daniel Vetter Mail: daniel at ffwll.ch Mobile: +41 (0)79 365 57 48
