[RFC 10/12] omap: mcbsp: Move sidetone clock management to mach-omap2/mcbsp.c

[Paul Walmsley]

+ Benoît

Hello Jarkko

On Fri, 1 Jul 2011, Jarkko Nikula wrote:

> Active sidetone requires that McBSP interface clock doesn't idle and there
> is no mechanism in hwmod to turn autoidling on/off in runtime. McBSP2 and 3
> in OMAP34xx share their interface clock with McBSP sidetone module and
> that interface clock must be active when the sidetone is operating.
> 
> Sidetone has its own autoidle bit which should keep the interface clock
> active but it is broken. Putting the McBSP core to no-idle mode when the
> sidetone is active is no good either since it results to higher power
> consumption when using the threshold based DMA transfers.

In the hwmod code/data, we've got the OCPIF_SWSUP_IDLE flag that can be 
set on a struct omap_hwmod_ocp_if.  I think this is probably what's needed 
here.  The only problem is that we haven't linked that to the clock code 
to deny idle on the interface clock yet (see omap_hwmod.c:_setup()).  
Adding that code in, plus adding that OCPIF_SWSUP_IDLE flag to the 
McBSP2/3 data, seems like the right approach here.

I guess we also will need some basic usecounting for denying idle in the 
clock code.

Otherwise these direct register manipulations of clock registers, outside 
the clock code, could turn into a mess :-(

At least it makes sense to move those out of the driver and into the 
arch/arm/*omap* code...


- Paul