Re: v3.4-rc4 DSS PM problem (Was: Re: Problems with 3.4-rc5)

[Tomi Valkeinen <tomi.valkeinen@ti.com>]

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On Fri, 2012-05-04 at 17:54 +0300, Tomi Valkeinen wrote:
> Hi Kevin, Paul,
> 
> On Fri, 2012-05-04 at 15:09 +0100, Joe Woodward wrote:
> 
> > > > Ok, I can replicate it now. It seems to be somehow PM related. I
> > > > normally have USB gadget stuff compiled into kernel so that I can
> > > boot
> > > > via nfsroot with usb. After disabling USB support from the kernel, I
> > > can
> > > > see synclosts.
> > > > 
> > > > I have no idea yet what could be causing this. I've also tried adding
> > > > the couple of DSS patches which are in queue for next merge window,
> > > that
> > > > force OPP100 when DSS is enabled. They don't seem to help.
> > > 
> > > Also, at least on my setup, the sync lost doesn't happen very quickly
> > > after starting the video output, but (I think) only when the system
> > > starts to idle. My init scripts generate keys for sshd and some other
> > > stuff, and no sync lost there, only just before the shell prompt do I
> > > get a sync lost.
> > > 
> > >  Tomi
> > > 
> > 
> > That sounds like the same as I'm seeing. It seems that the sync lost jumps 
> > around a bit, from almost immediately (when the graphics are enabled), to 
> > up to 3 or 4 seconds later (still just before the shell prompt).
> > 
> > I'm assuming that setting the FIFO low and high points fixes your sync losts 
> > as well (as in the first patch you sent)?
> > 
> > I've also noted that doing things in different orders can sometimes fix the 
> > sync lost (such as disabling or enabling DVI output), but this all seems a bit 
> > random.
> > 
> > I'm just glad someone else has been able to replicate the problem :p
> 
> Kevin, Paul, there seems to be a problem with DSS on v3.4-rc4 running on
> omap3, causing DSS losing sync. I didn't notice this earlier as I have
> USB gadget compiled into my kernel. Removing USB support from the kernel
> causes the problem to appear, which more or less hints at a PM related
> issue.

Sorry, not sync lost, but FIFO underflow. So DSS is unable to fetch
enough pixels to update the panel. And in this case the pixel clock is
very low (small panel), so it's nowhere near any limit.

 Tomi


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