[Bug 103963] New: [CNL] eDP flicker at 4k

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=103963

            Bug ID: 103963
           Summary: [CNL] eDP flicker at 4k
           Product: DRI
           Version: DRI git
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: DRM/Intel
          Assignee: intel-gfx-bugs at lists.freedesktop.org
          Reporter: rodrigo.vivi at gmail.com
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
                CC: intel-gfx-bugs at lists.freedesktop.org

Created attachment 135787
  --> https://bugs.freedesktop.org/attachment.cgi?id=135787&action=edit
reg dump bios (before i915 gets loaded)

After i915 takes control and do the modeset on eDP 4k screen starts flickering
badly.
No Fifounderun detected.
Just some continuously short pulses happening.

[18272.883143] [drm:intel_get_hpd_pins [i915]] hotplug event received, stat
0x01000000, dig 0x11101010, pins 0x00000010
[18272.893693] [drm:intel_hpd_irq_handler [i915]] digital hpd port A - short
[18272.900528] [drm:intel_dp_hpd_pulse [i915]] got hpd irq on port A - short
[18272.907916] [drm:intel_dp_read_dpcd [i915]] DPCD: 12 14 84 41 00 00 01 01 02
00 00 00 00 0b 00
[18274.252425] [drm:intel_get_hpd_pins [i915]] hotplug event received, stat
0x01000000, dig 0x11101010, pins 0x00000010
[18274.262964] [drm:intel_hpd_irq_handler [i915]] digital hpd port A - short
[18274.269800] [drm:intel_dp_hpd_pulse [i915]] got hpd irq on port A - short
[18274.277217] [drm:intel_dp_read_dpcd [i915]] DPCD: 12 14 84 41 00 00 01 01 02
00 00 00 00 0b 00
[18277.343929] [drm:edp_panel_vdd_off_sync [i915]] Turning eDP port A VDD off
[18277.350973] [drm:edp_panel_vdd_off_sync [i915]] PP_STATUS: 0x80000008
PP_CONTROL: 0x00000067
[18277.359426] [drm:intel_power_well_disable [i915]] disabling DC off
[18277.365650] [drm:skl_enable_dc6 [i915]] Enabling DC6
[18277.370710] [drm:gen9_set_dc_state [i915]] Setting DC state from 00 to 02
[18277.377545] [drm:intel_power_well_disable [i915]] disabling AUX A
[18278.110030] [drm:intel_get_hpd_pins [i915]] hotplug event received, stat
0x01000000, dig 0x11101010, pins 0x00000010
[18278.120569] [drm:intel_hpd_irq_handler [i915]] digital hpd port A - short
[18278.127395] [drm:intel_dp_hpd_pulse [i915]] got hpd irq on port A - short
[18278.134240] [drm:intel_power_well_enable [i915]] enabling AUX A
[18278.140175] [drm:intel_power_well_enable [i915]] enabling DC off
[18278.146234] [drm:gen9_set_dc_state [i915]] Setting DC state from 02 to 00
[18278.153137] [drm:edp_panel_vdd_on [i915]] Turning eDP port A VDD on
[18278.159690] [drm:edp_panel_vdd_on [i915]] PP_STATUS: 0x80000008 PP_CONTROL:
0x0000006f
[18278.168120] [drm:intel_dp_read_dpcd [i915]] DPCD: 12 14 84 41 00 00 01 01 02
00 00 00 00 0b 00
[18278.795277] [drm:intel_get_hpd_pins [i915]] hotplug event received, stat
0x01000000, dig 0x11101010, pins 0x00000010
[18278.805816] [drm:intel_hpd_irq_handler [i915]] digital hpd port A - short
[18278.812664] [drm:intel_dp_hpd_pulse [i915]] got hpd irq on port A - short
[18278.820033] [drm:intel_dp_read_dpcd [i915]] DPCD: 12 14 84 41 00 00 01 01 02
00 00 00 00 0b 00
[18278.831152] [drm:intel_get_hpd_pins [i915]] hotplug event received, stat
0x01000000, dig 0x11101010, pins 0x00000010
[18278.841692] [drm:intel_hpd_irq_handler [i915]] digital hpd port A - short
[18278.848548] [drm:intel_dp_hpd_pulse [i915]] got hpd irq on port A - short
[18278.855920] [drm:intel_dp_read_dpcd [i915]] DPCD: 12 14 84 41 00 00 01 01 02
00 00 00 00 0b 00


By using fastboot=1 so reusing BIOS modeset everything just work and screen
doesn't flicker at all.
I tried to little by little not re-use what BIOS has done and we start having
flicker after we train the link ourselves.

All DBuf registers are set like the BIOS ones with same level.

Changes on the vswing tables and levels doesn't solve the issue.

Disabling watermarks doesn't help either.

Disabling all pm feature like dc states, rc6, keep power wells always on plus
leaving cdclock and voltage level at maximum values helps, but doesn't solve
the issue.

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