Re: [RFC,PATCH 1/2] Add a common struct clk

[Lothar Waßmann]

Hi,

Benjamin Herrenschmidt writes:
> On Fri, 2010-06-11 at 12:08 +0200, Lothar Waßmann wrote:
> > Hi,
> > 
> > > > > > Using a mutex in clk_enable()/clk_disable() is a bad idea, since that
> > > > > > makes it impossible to call those functions in interrupt context.
> > > IMHO if a device generates an irq its clock should already be on.  This
> > > way you don't need to enable or disable a clock in irq context.
> > >  
> > You may want to disable a clock in the IRQ handler. The VPU driver in
> > the Freescale BSP for i.MX51 does exactly this.
> > Anyway I don't see any reason for using a mutex here instead of
> > spin_lock_irq_save() as all other implementations do.
> 
> Because you suddenly make it impossible to sleep inside enable/disable
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^
???
All implementations so far use spin_lock_irq_save()!

How would you be able to sleep with a mutex held?
If you hold a lock you must not sleep, no matter what sort of lock it
is.


Lothar Waßmann
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