[Bug 107503] Native screen resolution not working correctly over HDMI LSPCON (i915)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=107503

--- Comment #4 from Nicholas Stommel <nicholas.stommel at gmail.com> ---
Created attachment 141030
  --> https://bugs.freedesktop.org/attachment.cgi?id=141030&action=edit
dmesg-drm-tip

Well, it seems I spoke too soon. This issue is *very* much still present on
drm-tip, but for some odd reason I could not reproduce it with drm.debug=0x1e.
Fredrik from https://bugzilla.redhat.com/show_bug.cgi?id=1570392 was also
unable to reproduce the bug using the "drm.debug=0x1e" kernel parameter.
Without using the debugging parameter, the incorrect native resolution bug most
certainly happens.

-- Occurrence: Happens roughly over a third of the time, resolution is
incorrect on boot.
-- Chipset: Intel® Core™ i7-7700T CPU using Intel® HD Graphics 630 (Kaby Lake
GT2)
-- System architecture: x86_64
-- Kernel version (drm-tip) 4.18.0-994-generic
-- Linux distribution: Ubuntu 18.04.1 LTS (also confirmed on Fedora 28, appears
distro-independent)
-- Machine: HP Elitedesk 800 G3 DM 35W
-- Display connector: LSPCON HDMI

I have attached the dmesg from boot without the drm.debug=0x1e kernel
parameter, I will keep trying to see if I can replicate the bug with this
parameter to get the full debugging dmesg. Here you can clearly see in the
dmesg sans debugging parameter the lines:

[drm:lspcon_wait_mode [i915]] *ERROR* LSPCON mode hasn't settled
[drm:intel_dp_get_link_train_fallback_values [i915]] *ERROR* Link Training
Unsuccessful

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