On Fri, 2012-01-13 at 22:20 +1100, NeilBrown wrote: > Having CPUIDLE makes the DSS2 problem worse: lots of > > [ 21.085113] omapdss DISPC error: SYNC_LOST on channel lcd, > restarting the output with video overlays disabled > > messages whenever the CPU isn't busy.
I'm not sure if it is the case here, but DSS has restrictions about the max DSS clocks on different OPPs. For example, on OMAP4430 LCD clock maximum is 186MHz at OPP100, and 93MHz at OPP50. So it's a quite big drop, causing problems with all but the rather small displays. And the DSS driver doesn't have any support to handle this at the moment, as there isn't support in the PM framework to do this. I think the only way to handle this at the moment is for the DSS driver to set an arbitrarily high constraint on, say, mem throughput, and hope that it keeps the OMAP in the required OPP. Tomi
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