linux-kernel - Re: [PATCH 1/2] Add a common struct clk

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Date:	Tue, 11 Jan 2011 12:22:40 +0100
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Jeremy Kerr <jeremy.kerr@...onical.com>
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Ben Herrenchmidt <benh@...nel.crashing.org>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Subject: Re: [PATCH 1/2] Add a common struct clk

On Tue, Jan 11, 2011 at 06:27:11PM +0800, Jeremy Kerr wrote:
> Hi Sascha,
>  
> > The i.MX clk implementation disables the old parent if clk is enabled
> > and enables the new parent if clk is enabled (modulo bugs). Shouldn't
> > we do this here aswell?
> 
> Sounds reasonable, yes.
> 
> > I thought about returning -EBUSY if clk_set_parent is called for an
> > enabled clk, but this way we could never reparent the cpu clock which I
> > think is done in the Freescale BSP for power saving.
> 
> I think that the possibility for changing the parent really depends on the 
> implementation; in some cases we may want to disallow it, in others it might 
> be fine.
> 
> Related: do we really need globally-accessible clk_{get,set}_parent in the clk 
> API? For cases where we need to set the parent, we probably need details about 
> the platform clock configuration (eg, which clocks are possible parents). In 
> this case, we could just call into the clock driver directly.

I agree that drivers have no business calling clk_{get,set}_parent, this
is purely platform specific.

Sascha

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