We don't actually check for INTEL_OUTPUT_DP_MST at all in here, as a
result we skip assigning a DPLL to any DP MST ports, which makes link
training fail:

[ 1442.933896] [drm:intel_power_well_enable] enabling DDI D power well
[ 1442.933905] [drm:skl_set_power_well] Enabling DDI D power well
[ 1442.933957] [drm:intel_mst_pre_enable_dp] 0
[ 1442.935474] [drm:intel_dp_set_signal_levels] Using signal levels 00000000
[ 1442.935477] [drm:intel_dp_set_signal_levels] Using vswing level 0
[ 1442.935480] [drm:intel_dp_set_signal_levels] Using pre-emphasis level 0
[ 1442.936190] [drm:intel_dp_set_signal_levels] Using signal levels 05000000
[ 1442.936193] [drm:intel_dp_set_signal_levels] Using vswing level 1
[ 1442.936195] [drm:intel_dp_set_signal_levels] Using pre-emphasis level 1
[ 1442.936858] [drm:intel_dp_set_signal_levels] Using signal levels 08000000
[ 1442.936862] [drm:intel_dp_set_signal_levels] Using vswing level 2
…
[ 1442.998253] [drm:intel_dp_link_training_clock_recovery [i915]] *ERROR* too many full retries, give up
[ 1442.998512] [drm:intel_dp_start_link_train [i915]] *ERROR* failed to train DP, aborting

After which the pipe state goes completely out of sync:

[   70.075596] [drm:check_crtc_state] [CRTC:25]
[   70.075696] [drm:intel_pipe_config_compare [i915]] *ERROR* mismatch in ddi_pll_sel (expected 0x00000000, found 0x00000001)
[   70.075747] [drm:intel_pipe_config_compare [i915]] *ERROR* mismatch in shared_dpll (expected -1, found 0)
[   70.075798] [drm:intel_pipe_config_compare [i915]] *ERROR* mismatch in dpll_hw_state.ctrl1 (expected 0x00000000, found 0x00000021)
[   70.075840] [drm:intel_pipe_config_compare [i915]] *ERROR* mismatch in dpll_hw_state.cfgcr1 (expected 0x00000000, found 0x80400173)
[   70.075884] [drm:intel_pipe_config_compare [i915]] *ERROR* mismatch in dpll_hw_state.cfgcr2 (expected 0x00000000, found 0x000003a5)
[   70.075954] [drm:intel_pipe_config_compare [i915]] *ERROR* mismatch in base.adjusted_mode.crtc_clock (expected 262750, found 72256)
[   70.075999] [drm:intel_pipe_config_compare [i915]] *ERROR* mismatch in port_clock (expected 540000, found 148500)

And if you're especially lucky, it keeps going downhill:

[   83.309256] Kernel panic - not syncing: Timeout: Not all CPUs entered broadcast exception handler
[   83.309265]
[   83.309265] =================================
[   83.309266] [ INFO: inconsistent lock state ]
[   83.309267] 4.5.0-rc1Lyude-Test #265 Not tainted
[   83.309267] ---------------------------------
[   83.309268] inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
[   83.309270] Xorg/1194 [HC0[1]:SC0[0]:HE1:SE1] takes:
[   83.309293]  (&(&dev_priv->uncore.lock)->rlock){?.-...}, at: [<ffffffffa02a6073>] gen9_write32+0x63/0x400 [i915]
[   83.309293] {IN-HARDIRQ-W} state was registered at:
[   83.309297]   [<ffffffff810e84f4>] __lock_acquire+0x9c4/0x1d00
[   83.309299]   [<ffffffff810ea1be>] lock_acquire+0xce/0x1c0
[   83.309302]   [<ffffffff8177d936>] _raw_spin_lock_irqsave+0x56/0x90
[   83.309321]   [<ffffffffa02a5492>] gen9_read32+0x52/0x3d0 [i915]
[   83.309332]   [<ffffffffa024beea>] gen8_irq_handler+0x27a/0x6a0 [i915]
[   83.309337]   [<ffffffff810fdbc1>] handle_irq_event_percpu+0x41/0x300
[   83.309339]   [<ffffffff810fdeb9>] handle_irq_event+0x39/0x60
[   83.309341]   [<ffffffff811010b4>] handle_edge_irq+0x74/0x130
[   83.309344]   [<ffffffff81009073>] handle_irq+0x73/0x120
[   83.309346]   [<ffffffff817805f1>] do_IRQ+0x61/0x120
[   83.309348]   [<ffffffff8177e6d6>] ret_from_intr+0x0/0x20
[   83.309351]   [<ffffffff815f5105>] cpuidle_enter_state+0x105/0x330
[   83.309353]   [<ffffffff815f5367>] cpuidle_enter+0x17/0x20
[   83.309356]   [<ffffffff810dbe1a>] call_cpuidle+0x2a/0x50
[   83.309358]   [<ffffffff810dc1dd>] cpu_startup_entry+0x26d/0x3a0
[   83.309360]   [<ffffffff817701da>] rest_init+0x13a/0x140
[   83.309363]   [<ffffffff81f2af8e>] start_kernel+0x475/0x482
[   83.309365]   [<ffffffff81f2a315>] x86_64_start_reservations+0x2a/0x2c
[   83.309367]   [<ffffffff81f2a452>] x86_64_start_kernel+0x13b/0x14a

Fixes: 82d35437 ("drm/i915/skl: Implementation of SKL DPLL programming")
Signed-off-by: Lyude <cpaul@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1454428183-994-1-git-send-email-cpaul@redhat.com
(cherry picked from commit 78385cb3)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>