linux-kernel - Re: [RFC PATCH] clk: add extension API

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Date:	Thu, 31 May 2012 12:26:05 +0300
From:	Felipe Balbi <balbi@...com>
To:	Peter De Schrijver <pdeschrijver@...dia.com>
Cc:	Felipe Balbi <balbi@...com>, Stephen Boyd <sboyd@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Mike Turquette <mturquette@...com>
Subject: Re: [RFC PATCH] clk: add extension API

Hi,

On Thu, May 31, 2012 at 12:05:18PM +0300, Peter De Schrijver wrote:
> > 
> > What if a module needs two clocks and you drive the reset on both of the
> > clocks ? What would happen ?
> > 
> 
> Only 'leave clocks' have this reset method and a module can only have 1 of
> them.

fair enough... got mislead by you "every module has at least one clock"
statement.

> > > but then we would have the keep a list of IDs (1 per module) which the drivers
> > > can use to call some tegra reset function which would in the end use registers
> > > in the same memory area to cause a reset. (the registers controlling
> > > modulereset are interleaved with those controlling the enable/disable of the
> > > main moduleclock and bitpositions are identical)
> > 
> > Well, under a generic device-level API, you could just call an internal
> > clk_reset() function because you know which clocks feed into which
> > devices anyway. It could look something like:
> > 
> > on Tegra:
> > 
> > device_reset(dev)
> > 	-> dev_pm_domain->reset()
> > 		-> tegra_periph_reset()
> > 
> 
> These methods are also needed internally by the powergating code.

so ? Just call them when you need...

> > on OMAP:
> > 
> > device_reset(dev)
> > 	-> dev_pm_domain->reset()
> > 		-> omap_hwmod_reset()
> > 
> > 
> > btw:
> > 
> > tegra_periph_reset(....)
> > {
> > 	tegra_periph_reset_assert(...);
> > 	udelay(2);
> > 	tegra_periph_reset_deassert(...);
> > }
> 
> which uses the clockframework currently.

no problems there. The point is that you already know which clock feed
into which device, so if you have a device-based API for device
soft-reset, you can figure out which exact clock to toggle, right ?

-- 
balbi

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