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

From: Ben Dooks
Date: Sun Jun 13 2010 - 18:27:35 EST

On Fri, Jun 11, 2010 at 12:08:01PM +0200, Lothar Wa?mann 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.

Hmm, then again the VPU driver may just be a bit wrong here.

We could protect each clock with a spinlock, but that would end up
with a problem of spinning where we have clocks that takes 100s of
usec or so to init. See all PLLs on S3C devices, where it can take
100-300uS to get a stable clock out of the device.

Ben (ben@xxxxxxxxx,

'a smiley only costs 4 bytes'
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