Re: The clock problem in OMAP2 McSPI

[David Brownell <david-b@pacbell.net>]

On Thursday 16 August 2007, Kyungmin Park wrote:
> After booting, it oops with following messages[2].
> 
> So I reverted only clock parts as before. Then it's work well.
> I think it has some clock problem.
> 
> Do you have any idea?

Nope, sorry.  I looked at that driver code, and what I
see is neatly paired clk_enable()/clk_disable() calls ...
stuff that should be "obviously correct".  And which
works fine here...

I don't see how that should be able to cause a disable()
of something that's already got usecount 0.

I wouldn't *think* that the updates in the clock framework
have caused problems.  But regardless, to debug this I'd
start by tracing the refcounts of that functional clock.

The only slightly odd unusual thing in that driver should
be that the two clocks would normally be disabled until
there's some I/O to be done (either to the McSPI registers
or to a SPI device).  Most drivers leave clocks enabled all
the time, needlessly wasting power.

- Dave