Re: Common clock framework API vs RT patchset

[Felipe Balbi <balbi@ti.com>]

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On Wed, Aug 12, 2015 at 09:46:49AM -0700, Michael Turquette wrote:
> Quoting Felipe Balbi (2015-08-12 08:02:53)
> > On Wed, Aug 12, 2015 at 11:11:51AM +0100, Russell King - ARM Linux wrote:
> > > On Wed, Aug 12, 2015 at 01:05:58PM +0300, Grygorii Strashko wrote:
> > > > On 08/12/2015 01:06 AM, Michael Turquette wrote:
> > > > > Quoting Russell King - ARM Linux (2015-08-11 12:25:15)
> > > > >>
> > > > >> clk_enable/clk_disable _should_ be usable from atomic contexts.
> > > > 
> > > > Thanks Russell - above is not true on -RT.
> > > 
> > > What I'm saying is that it _should_ be true.  You _should_ be able to
> > > call clk_enable()/clk_disable() from atomic contexts.  It's been
> > > documented since forever:
> > > 
> > > /**
> > >  * clk_enable - inform the system when the clock source should be running.
> > >  * @clk: clock source
> > >  *
> > >  * If the clock can not be enabled/disabled, this should return success.
> > >  *
> > >  * May be called from atomic contexts.
> > > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > > 
> > > /**
> > >  * clk_disable - inform the system when the clock source is no longer required.
> > >  * @clk: clock source
> > >  *
> > >  * Inform the system that a clock source is no longer required by
> > >  * a driver and may be shut down.
> > >  *
> > >  * May be called from atomic contexts.
> > > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> > > 
> > > If that's not true with CCF, that's a CCF bug, not a usage bug.
> > 
> > in that case, CCF's clock need to be converted to raw_spin_locks, that's
> > the only way to prevent its locks from being reimplemented as rt
> > mutexes.
> 
> I do not keep up much with rt stuff, so I am going to ask a naive
> question: is it common to simply do s/spin_lock/raw_spin_lock/g for
> driver subsystems when using rt? Sounds like that is all that is
> required...

depends, if you want to guarantee your code isn't preemptable, then
yeah.

-- 
balbi

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