Created attachment 129490 [details] [review] drm/i915: Fix DisplayPort Hotplug I recently updated to Linux 4.9 (via Gentoo's kernel, but I used Linus' git tree when bisecting and fixing the bug, and it appears on v4.9 there as well) and discovered that my DisplayPort monitor doesn't come back from sleep any more. I bisected the problem back to commit 7d23e3c37bb3fc6952dc84007ee60cb533fd2d5c Author: Shubhangi Shrivastava <shubhangi.shrivastava@intel.com> Date: Wed Mar 30 18:05:23 2016 +0530 drm/i915: Cleaning up intel_dp_hpd_pulse Current DP detection has DPCD operations split across intel_dp_hpd_pulse and intel_dp_detect which contains duplicates as well. Also intel_dp_detect is called during modes enumeration as well which will result in multiple dpcd operations. So this patch tries to solve both these by bringing all DPCD operations in one single function and make intel_dp_detect use existing values instead of repeating same steps. This looks a whole lot like <https://bugs.freedesktop.org/show_bug.cgi?id=89453>, and the fix looks really similar too, but the bug is still there on 4.9 so it's not a duplicate. I've attached a patch that fixes the problem for me when applied on top of 4.9. It applies cleanly on Linus' master, but I haven't tried running it.
Can you add a signed-off-by for your patch (See Developer's Certificate of Origin 1.1 in Documentation/process/submitting-patches.rst) and send it to intel-gfx@lists.freedesktop.org? Or just add an s-o-b here and I'll send it on.
I sent the patch
Created attachment 129515 [details] [review] drm/i915: Fix DisplayPort Hotplug I don't see my message in the intel-gfx mailing list archive so I'm worried it got lost somehow. I've attached the patch I sent out here, just in case.
http://patchwork.freedesktop.org/patch/msgid/20170210224420.13488-1-palmer@dabbelt.com
I'm experiencing the same issue on a PA328Q connected via DisplayPort. It must be doing something weird with the HPD line. When the monitor comes out of standby it is not detected by my stock GNOME 3 environemnt. I have to manually turn if off and on again to use it properly. Seems like all newer ASUS monitor seem to be affected by this behaviour. I'm on drm-intel-nightly which is currently based on 4.11-rc5.
Ville has patch: https://patchwork.freedesktop.org/series/19601/
commit 1a36147bb93921651f7fbd7a6e522da6c349081b Author: Ville Syrjälä <ville.syrjala@linux.intel.com> Date: Wed Apr 12 22:30:17 2017 +0300 drm/i915: Perform link quality check unconditionally during long pulse
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