<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_ASSIGNED " title="ASSIGNED - Screen is frozen on second connection of DP MST dock" href="https://bugs.freedesktop.org/show_bug.cgi?id=107546#c38">Comment # 38</a> on <a class="bz_bug_link bz_status_ASSIGNED " title="ASSIGNED - Screen is frozen on second connection of DP MST dock" href="https://bugs.freedesktop.org/show_bug.cgi?id=107546">bug 107546</a> from <a class="email" href="mailto:stanislav.lisovskiy@intel.com" title="Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>"> Stanislav Lisovskiy</a> <pre>(In reply to Vedran Furač from <a href="show_bug.cgi?id=107546#c34">comment #34</a>) > Hello, > > I think I have the same issue on Intel's NUC7i5BNB with dual Dell monitors > using daisy chain (and 3rd over HDMI). I've tested many kernels and have > come to conclusion the the problem was first introduced in 4.11 and various > manifestation of it appear in all subsequent kernels up to 4.19-rc7 from > Debian. Kernels 4.9 and 4.10 work fine. > > To reproduce it, all I need to do is switch input using primary Dell OSD > from DP to mDP (nothing on it) and then switch back to DP input. This > results in flood of: > > [1615629.735590] [drm:intel_ddi_prepare_link_retrain [i915]] *ERROR* Timeout > waiting for DDI BUF C idle bit > [1615629.811616] [drm:intel_dp_start_link_train [i915]] *ERROR* Timed out > waiting for DP idle patterns > > messages and the X server is frozen. SSH works normally, but if I try to > restart X, system usually hard locks and I need to cut the power (not even > sysrq magic works). I was unable to find any workarounds. With 4.18 there's > even kernel oops (after returning to DP input): > > [ 321.495462] [drm:intel_dp_check_mst_status [i915]] got esi 42 10 00 > [ 321.497662] BUG: unable to handle kernel NULL pointer dereference at > 0000000000000000 > [ 321.497665] PGD 0 P4D 0 > [ 321.497667] Oops: 0000 [#1] SMP NOPTI > [ 321.497669] CPU: 1 PID: 188 Comm: kworker/u8:3 Tainted: G U O > 4.18.0-2-amd64 #1 Debian 4.18.10-2 > [ 321.497670] Hardware name: /NUC7i5BNB, BIOS > BNKBL357.86A.0049.2017.0724.1541 07/24/2017 > [ 321.497689] Workqueue: i915-dp i915_digport_work_func [i915] > [ 321.497692] RIP: 0010:refcount_inc_not_zero+0x0/0x50 > [ 321.497693] Code: c0 74 02 f3 c3 80 3d 64 bb d3 00 00 75 f5 48 c7 c7 70 > 9a 07 84 c6 05 54 bb d3 00 01 e8 f9 f3 cb ff 0f 0b c3 66 0f 1f 44 00 00 <8b> > 07 85 c0 8d 50 01 74 35 85 d2 74 0b f0 0f b1 17 75 ef 83 fa ff > [ 321.497712] RSP: 0018:ffffa1f8c37c7d18 EFLAGS: 00010246 > [ 321.497713] RAX: 0000000000000000 RBX: ffff935493b129c8 RCX: > 0000000000000000 > [ 321.497714] RDX: ffff93549270bd00 RSI: 0000000000000001 RDI: > 0000000000000000 > [ 321.497715] RBP: 0000000000000000 R08: 00000000fffffffa R09: > 0000000000000002 > [ 321.497716] R10: ffffa1f8c37c7cf0 R11: 0000000000000102 R12: > ffff935493b12870 > [ 321.497717] R13: 0000000000000001 R14: ffffa1f8c37c7dc2 R15: > ffff935493b12700 > [ 321.497718] FS: 0000000000000000(0000) GS:ffff9354be880000(0000) > knlGS:0000000000000000 > [ 321.497720] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 321.497721] CR2: 0000000000000000 CR3: 00000001dda0a001 CR4: > 00000000003606e0 > [ 321.497722] Call Trace: > [ 321.497725] refcount_inc+0x5/0x30 > [ 321.497730] drm_dp_get_mst_branch_device+0xc2/0xe0 [drm_kms_helper] > [ 321.497735] drm_dp_mst_hpd_irq+0x104/0x8c0 [drm_kms_helper] > [ 321.497750] ? intel_dp_check_mst_status+0xba/0x1e0 [i915] > [ 321.497763] intel_dp_check_mst_status+0xba/0x1e0 [i915] > [ 321.497776] intel_dp_hpd_pulse+0x176/0x2e0 [i915] > [ 321.497778] ? __switch_to_asm+0x40/0x70 > [ 321.497791] i915_digport_work_func+0x8f/0x120 [i915] > [ 321.497794] process_one_work+0x195/0x370 > [ 321.497795] worker_thread+0x30/0x390 > [ 321.497797] ? process_one_work+0x370/0x370 > [ 321.497799] kthread+0x113/0x130 > [ 321.497800] ? kthread_create_worker_on_cpu+0x70/0x70 > [ 321.497802] ret_from_fork+0x35/0x40 > > > I'll attach full debug output. > > Regards, > Vedran The backtrace attached here indicates that this is possibly a duplicate of <a class="bz_bug_link bz_status_RESOLVED bz_closed" title="RESOLVED FIXED - USB-C dock unplug trigger NULL pointer access" href="show_bug.cgi?id=108616">https://bugs.freedesktop.org/show_bug.cgi?id=108616</a>. Can you please try the fix, which is proposed there?</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are on the CC list for the bug.</li> <li>You are the QA Contact for the bug.</li> </ul> </body> </html>