Bug 109141 - 12bpc hdmi causes wrong real refresh rate (swapbuffers return time)
Summary: 12bpc hdmi causes wrong real refresh rate (swapbuffers return time)
Status: RESOLVED CODE_FIX
Alias: None
Product: Drivers
Classification: Unclassified
Component: Video(DRI - Intel) (show other bugs)
Hardware: Intel Linux
: P1 normal
Assignee: intel-gfx-bugs@lists.freedesktop.org
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2015-12-09 11:46 UTC by Kevin Mitchell
Modified: 2016-01-17 03:34 UTC (History)
2 users (show)

See Also:
Kernel Version: 4.3
Subsystem:
Regression: No
Bisected commit-id:


Attachments
Samsung un40eh5000 edid reported by xrandr --prop (513 bytes, text/plain)
2015-12-09 11:46 UTC, Kevin Mitchell
Details
above edid decoded by edid-decode (3.19 KB, text/plain)
2015-12-09 11:47 UTC, Kevin Mitchell
Details

Description Kevin Mitchell 2015-12-09 11:46:37 UTC
Created attachment 196911 [details]
Samsung un40eh5000 edid reported by xrandr --prop

I have a Samsung un40eh5000 tv that I connect to my Ivy Bridge Lenovo T530 laptop via mini display-port to hdmi. I have attached the raw and decoded EDID. 

As of 7a0baa6234468aa387f9b8a1a79dc2a4b4821f67, it seems 12bpc gets enabled on this setup (though I can't imagine that my machine or my TV actually support that in real life). Unfortunately, this seems to change the effective refresh rate as measured between returns from opengl swapbuffers calls for example in glxgears.

       | glxgears fps   |
       +----------------+
xrandr | before | after |
-------+--------+-------+
23.98  | 24.00  | 23.85 |
24.00  | 24.00  | 24.13 |
29.97  | 30.00  | 29.81 |
30.00  | 30.00  | 30.17 |
59.94  | 60.00  | 60.12 |
60.00  | 60.00  | 60.12 |

This is problematic for displaying video at native frame rates. For example when the actual refresh rate of 24.00 hz could be achieved, 23.98fps video would only have to repeat a frame every 50 seconds. Now it must either drop or repeat one every 7 seconds which is much more noticeable.
Comment 1 Kevin Mitchell 2015-12-09 11:47:27 UTC
Created attachment 196931 [details]
above edid decoded by edid-decode
Comment 2 Jani Nikula 2015-12-09 14:23:57 UTC
Please file new i915 bugs at the freedesktop.org bugzilla
https://bugs.freedesktop.org/enter_bug.cgi?product=DRI&component=DRM/Intel
Comment 3 Kevin Mitchell 2015-12-10 01:23:37 UTC
so by "new bugs" you mean I should *not* re-report this there?
Comment 4 Kevin Mitchell 2016-01-17 03:34:35 UTC
reopened at 

https://bugs.freedesktop.org/show_bug.cgi?id=93361

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