Re: PM(?) problems on v3.3-rc1 on OMAP3

Tomi Valkeinen
2012-01-23T08:25:49Z

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On Sun, 2012-01-22 at 07:46 +1100, NeilBrown wrote:
> On Sat, 21 Jan 2012 17:57:07 +0200 Tomi Valkeinen <tomi.valkeinen@ti.com>
> wrote:

> > In this case something is affecting the DSS (clocks? powers?), or the
> > memory, or the process of reading the pixels. I really don't see the MPU
> > or IRQs affecting this problem, except indirectly.
>
> Which clocks, exactly, are important?
>
> I collected some clock.c tracing while dss was repeatedly complaining about
> losing SYNC, and notice that omap_96m_fck was being enabled and disabled in
> hardware.
> omap_96m_fck is upstream for dss_96m_fck which provides the tv_dac_clk.
>
> Could it be this clock turning on and off which causes the problem?

I don't think 96m clock is important. At least I'm testing with plain
DPI, not tv-out. And I think missing 96m clock would just lead to a
missing image on the tv, not sync losts.

For OMAP3 DSS when using DPI the following clocks are important:

DPLL4_ALWON_FCLKOUTM4X2 (i.e. DSS1_ALWON_FCLK) (dss func clock)
DSS_L3_ICLK (to fetch pixels)
DSS_L4_ICLK (to configure dss registers)

I don't think any other clocks are used.

Tomi

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