On Wed, 2012-05-16 at 12:08 +0300, Tomi Valkeinen wrote: > On Tue, 2012-05-15 at 11:55 -0600, Paul Walmsley wrote: > > Hello Tomi, > > > > On Mon, 14 May 2012, Tomi Valkeinen wrote: > > > > > I've been doing testing to understand the problem, but so far I don't > > > have any idea why things go wrong. I haven't found out any logic in > > > which configuration works and which doesn't. Looks to me that for some > > > reason the PM prevents DSS from getting data fast enough with certain > > > fifo thresholds. > > > > > > I have two ways to avoid the problem, but I've been reluctant to make > > > patches for those because I feel it's just hiding the problem. One way > > > is to change DISPC SIDLEMODE or MIDLEMODE to disallow idle/standby. The > > > other is to use certain fifo threshold values, which just seem to work > > > for unknown reasons. > > > > > > Considering that we already have a SIDLEMODE hack in DSS for omap3 when > > > using DSI, I wonder if the omap3 PM + DSS combination is just plain > > > broken, and we should disallow idle. I'm not quite sure what are the > > > implications of that. > > > > > > I'd appreciate comments from the PM people =). > > > > This may be caused by one of the DPLLs going into autoidle. This can > > involve a significant wakeup latency. I'd suggest looking at DPLL3, which > > provides the DSS interface clock, and DPLL4, which can provide the DSS > > functional clock. > > > > Could you try: > > > > 1. applying something like the patch at the bottom of this message and > > seeing if it makes any difference? > > > > 2. if #1 does not work, changing the "dpll3" in the patch to "dpll4" ? > > > > 3. if #2 does not work, disabling autoidle on both dpll3 and dpll4? > > Disabling DPLL3 autoidle fixes the problem. Disabling DPLL4 autoidle > doesn't affect the problem. JFYI, I also tested changing DISPC's SYSCONFIG:CLOCKACTIVITY, which, to me, sounds a bit related to dpll autoidle. By default it's 0, "interface and functional clocks can be switched off". I tested the three other values, but none of them had any effect. Tomi
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