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

From: Uwe Kleine-König
Date: Mon Jun 14 2010 - 05:43:25 EST

On Mon, Jun 14, 2010 at 11:30:08AM +0200, Lothar Waßmann wrote:
> Benjamin Herrenschmidt writes:
> > On Mon, 2010-06-14 at 08:39 +0200, Lothar Waßmann wrote:
> > > All implementations so far use spin_lock_irq_save()!
> >
> > Nothing prevents your implementation to be a tad smarter.
> >
> I vote for consistency, so that device drivers can be kept arch
> independent instead of having to care about implentation details of
> each arch.
Back when I implemented clock support for ns9xxx (unfortunately not in
mainline) I tried with a spinlock first and later switched to a mutex.
IIRC the reason was that on ns9215 enabling the rtc clock took long
(don't remember a number) and successfull enabling was signaled by an
irq. So I would have had to implement irq polling in the clock code.

I think you can find different examples that make both possiblities bad.
All in all I think that a sleeping clock implementation is preferable as
it improves (general) latencies.

Best regards

Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | |
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