Letux Kernel

Issue 703: Anti-Tearing

Reported by Nikolaus Schaller, Oct 26, 2015

OMAP5 DSI (MIPI) interface does not honour the Tearing Input (VSYNC) 
in "Video Mode". Rather, the VSYNC frequency and phase is 
defined by the DISPC settings.

The SSD2858 has its own VSYNC and frame timing generator and drives 
the panel autonomously.

Tearing appears since the VSYNC of the DISPC and VSYNC of the 
SSD2858 are not synchronized and may even have slightly different 
frequencies (clock oscillators are separate and have drift and 
divider factors can not be found to give an exact match).

Anti-Tearing should work as follows:
* enable TE-input of OMAP5 DSI as gpio interrupt
* make SSD output VSYNC to the TE-input
* detect the timing relationship between the DISPC VSYNC irq and the 
TE-input irq
* if they are close enough, do nothing
* if they are too far away, adjust the vertical blanking period of 
the DISPC
* this may need some cycles to lock, but if locked the phase should 
be stable

Start with implementing into panel-mipi-debug driver.

Comment 1 by Nikolaus Schaller, Apr 22, 2016

Labels: Device:Pyra

Comment 2 by Nikolaus Schaller, Oct 29, 2016

Final Pyra will be using TILER and no SSD2858 so this is no more a 
problem.
Status: WontFix

Created: 3 years 10 months ago by Nikolaus Schaller

Updated: 2 years 10 months ago

Status: WontFix

Owner: Nikolaus Schaller

Labels:
Type:Defect
Priority:Critical
Device:Pyra