Created attachment 131199 [details] eagle lake dp dmesg HP Compaq 8000 E7500 displayport shows timeout errors in log, and doesn't come up at all. Monitor is IBM ThinkVision, connected with straight cable. VGA works. Default Ubuntu kernel and DRM-Tip show same symptoms: monitor shortly coming out of power save, then going back and no picture. BIOS screen shows up through DP well enough. DRM-Tip dmesg with drm.debug=0xe attached.
I'd like to see what 'intel_reg dump' has to say when the BIOS has enabled DP and you boot without loading i915. Note that intel_reg is currently broken, so you will need to use igt e7a0d06730f77842998368660fb45fe5c1738fda or older.
Created attachment 131207 [details] intel_reg dump Booted DRM-tip without i915.ko, created dump with old IGT version. Only monitor connected is DP where BIOS and grub show up.
OK, so definitely it' using port C. DP_C (0x00064200): 0xb01c001c This looks a little peculiar. The clock divider is based on a 266MHz clock, whereas we detect the rawclk as 200Mhz. DPC_AUX_CH_CTL (0x00064210): 0x40140085
Created attachment 131208 [details] [review] [PATCH] hack: Pretend rawclk 266Mhz This hack might help with getting AUX working.
Confirmed: this hack fixes DP issue with this particular HW.
(In reply to Tomi Sarvela from comment #5) > Confirmed: this hack fixes DP issue with this particular HW. I was almost hoping it wouldn't. Now we'd have to figure out what's wrong with out rawclk readout, but unfortunately the old configdb is gone so there are no docs anywhere that I know :(
Reference ti fix from Ville: https://patchwork.freedesktop.org/series/23978/
commit 6f38123ecaac446312a63523b68df84ceb5a06ed Author: Ville Syrjälä <ville.syrjala@linux.intel.com> Date: Thu May 4 21:15:30 2017 +0300 drm/i915: Fix rawclk readout for g4x
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