linux-kernel - Re: [PATCH 0/6] clk: Initial feedback for off-SoC slow bus clocks

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Message-ID: <20110711104625.GH26347@pengutronix.de>
Date:	Mon, 11 Jul 2011 12:46:25 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
Cc:	Grant Likely <grant@...retlab.ca>,
	patches@...nsource.wolfsonmicro.com, linux-sh@...r.kernel.org,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	linux-kernel@...r.kernel.org,
	Jeremy Kerr <jeremy.kerr@...onical.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 0/6] clk: Initial feedback for off-SoC slow bus clocks

On Mon, Jul 11, 2011 at 11:28:56AM +0100, Russell King - ARM Linux wrote:
> On Mon, Jul 11, 2011 at 12:07:59PM +0200, Sascha Hauer wrote:
> > On Mon, Jul 11, 2011 at 10:31:24AM +0100, Russell King - ARM Linux wrote:
> > > On Mon, Jul 11, 2011 at 11:53:44AM +0900, Mark Brown wrote:
> > > > The biggest issue I ran into was that as the clocks are all registered
> > > > by name with the API if you've got two instances of the same off-SoC
> > > > device in the system you'll not be able to disambiguate between the
> > > > clocks it provides.
> > > 
> > > Sigh.  That sounds like yet more trash.  Obviously whoever thought
> > > up that doesn't actually understand clks.
> > 
> > Nope. In the patches Jeremy posted clocks have a name, but this name
> > is not meant to be used with clk_get. clk_get is still implemented
> > in clkdev, so the matching between clocks and devices is independent
> > of the clock name.
> > 
> > In earlier versions of Jeremys patches the clock name was only present
> > when debugfs was compiled in and I think it can be changed back to this.
> > 
> > That said the debugfs support (which is not present in Jeremys latest
> > series) would break if two clocks with the same name have the same
> > parent, because the clock core would try to create to debugfs entries
> > with the same name.
> 
> If that's all its for, then can't some other solution for debugfs names
> (lets stop calling them clock names to avoid confusion) be found -
> such as
> 
> 	sprintf(debugfsname, "%s@%p", clk->debugfsprefix, clk);
> 

Sounds good. During my tests on i.MX I found it very convenient to have
speaking debugfs names, so I vote for this suggestion instead the
following ones.

> Or how about using something like this:
> 
> $debugfs/clkdev/device/connection -> ../../clk/<name-of-clk>
> $debugfs/clk/<name-of-clk>
> 
> where <name-of-clk> could just be the address of the struct clk (which
> eliminates the need to pass any names in) or some prefix plus an
> incrementing identifier, or just an incrementing number.
> 
> I did think about introducing such a scheme along with clkdev (and did
> have some code but that's long gone), but without the $debugfs/clk/ bit
> being standardized, it wouldn't have worked.
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

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