From mboxrd@z Thu Jan  1 00:00:00 1970
From: broonie@opensource.wolfsonmicro.com (Mark Brown)
Date: Mon, 26 Dec 2011 11:10:30 +0000
Subject: [PATCH v4 4/7] cpufreq: add clk-reg cpufreq driver
In-Reply-To: <20111224155227.GC1803@richard-laptop>
References: <1324537753-30590-1-git-send-email-richard.zhao@linaro.org>
 <1324537753-30590-5-git-send-email-richard.zhao@linaro.org>
 <20111223131851.GB13175@sirena.org.uk>
 <20111224085539.GA1892@richard-laptop>
 <20111224122411.GA13778@sirena.org.uk>
 <20111224132831.GB1803@richard-laptop>
 <20111224134227.GA20908@opensource.wolfsonmicro.com>
 <20111224155227.GC1803@richard-laptop>
Message-ID: <20111226111030.GC8722@opensource.wolfsonmicro.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Sat, Dec 24, 2011 at 11:52:29PM +0800, Richard Zhao wrote:
> On Sat, Dec 24, 2011 at 01:42:29PM +0000, Mark Brown wrote:
> > On Sat, Dec 24, 2011 at 09:28:33PM +0800, Richard Zhao wrote:

> > > If you think regulator thansition latency is board specific, then the board
> > > dts can overrite it.

> > We should just query this information from the regulator subsystem
> > (there's hooks but currently nothing implements them).  The regulators
> > can define their own bindings if they need to read it from device tree,
> > most of them should be able to do this as a function of knowing about
> > the device.  None of this is specific to cpufreq so cpufreq shouldn't
> > have to define its own support for this.

> I'd like to query the latency by call clk and regulator APIs. but as you said
> both of them have not implemented it yet. I think, for now, we can use the

The *call* is there in the regulator subsystem, it's just that none of
the drivers back it up with an actual implementation yet.  Which turns
out to be a good thing as cpufreq can't currently understand variable
latencies and the governors don't deal well with non-trivial latencies
anyway.

> property to get the total latency. Once I can get it at runtime, I'll remove
> it. So the definition of trans-latency is just the same as cpufreq transition_latency,
> people get less confused. What do you think?

The problem with device tree is that once you've defined a binding
you're stuck with it, it's very hard to change - witness all the magic
number based stuff with the interrupt bindings for example