From: Shawn Guo <shawn.guo@freescale.com>
To: Grant Likely <grant.likely@secretlab.ca>
Cc: Jamie Iles <jamie@jamieiles.com>,
Sascha Hauer <kernel@pengutronix.de>,
<devicetree-discuss@lists.ozlabs.org>,
<linux-kernel@vger.kernel.org>,
Rob Herring <rob.herring@calxeda.com>,
Mike Turquette <mturquette@ti.com>
Subject: Re: [RFC v2 4/9] of: add clock providers
Date: Thu, 15 Dec 2011 21:51:30 +0800 [thread overview]
Message-ID: <20111215135129.GA2831@S2100-06.ap.freescale.net> (raw)
In-Reply-To: <CACxGe6t50zJNpo=QWPzgFMpQ6Cfi9YZyrKuMSTrrA2oYiLF2Pw@mail.gmail.com>
On Tue, Dec 13, 2011 at 10:54:58AM -0700, Grant Likely wrote:
> On Mon, Dec 12, 2011 at 4:29 PM, Jamie Iles <jamie@jamieiles.com> wrote:
> > Hi Grant,
> >
> > I'm still going through these and trying to digest them but a couple of
> > quick questions/comments.
> >
> > Jamie
> >
> > On Mon, Dec 12, 2011 at 03:02:04PM -0700, Grant Likely wrote:
> >> diff --git a/Documentation/devicetree/bindings/clock/clock-bindings.txt b/Documentation/devicetree/bindings/clock/clock-bindings.txt
> >> new file mode 100644
> >> index 0000000..e40c436
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/clock/clock-bindings.txt
> >> @@ -0,0 +1,114 @@
> >> +This binding is a work-in-progress, and are based on some experimental
> >> +work by benh[1].
> >> +
> >> +Sources of clock signal can be represented by any node in the device
> >> +tree. Those nodes are designated as clock providers. Clock consumer
> >> +nodes use a phandle and clock specifier pair to connect clock provider
> >> +outputs to clock inputs. Similar to the gpio specifiers, a clock
> >> +specifier is an array of one more more cells identifying the clock
> >> +output on a device. The length of a clock specifier is defined by the
> >> +value of a #clock-cells property in the clock provider node.
> >> +
> >> +[1] http://patchwork.ozlabs.org/patch/31551/
> >> +
> >> +==Clock providers==
> >> +
> >> +Required properties:
> >> +#clock-cells: Number of cells in a clock specifier; typically will be
> >> + set to 1
> >
> > I'm not sure I fully understand what the extra cells actually mean for
> > clocks. I think the first integer is the clock output to use but some
> > of the versatile and highbank ones only have a phandle or is it more
> > implementation defined? The clock-output-names description hints at
> > recommended, so I find this a little confusing, but that could just be
> > me!
>
> I'm following convention here that has been established with
> interrupts, gpios, and others. Sometimes more information is needed
> that just the clock number. Using #clock-cells gives a clock provider
> the option of having additional fields for clock flags or other data.
> This is very much implementation defined. Simple clock providers that
> only have a single clock output can easily use #clock-cells = <0>.
> Providers with multiple outputs will need to use 1 or more cells.
>
It totally destroys my understanding on #clock-cells :)
I thought it's introduced to reduce the clock nodes in dts. That said,
#clock-cells stands for the number of clks we describe in the node.
When #clock-cells > 1 for a node, the node becomes a clk blob which
actually contains multiple clks. I migrated the imx6 clock to your
first post with this approach [1], using 70 nodes to describe 110
clocks (~35% nodes reduced).
Now, you are saying it's not designed for this purpose. I'm pretty
confused, because the only reasonable use of #clock-cells to me is
just that way, and I fail to see why we need #clock-cells if we do
not use it that way.
http://comments.gmane.org/gmane.linux.drivers.devicetree/9631
--
Regards,
Shawn
next prev parent reply other threads:[~2011-12-15 13:38 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-12 22:02 [RFC v2 1/9] arm/versatile*: merge all versatile struct clk definitions Grant Likely
2011-12-12 22:02 ` [RFC v2 2/9] arm/versatile*: Consolidate clk_ops and setvco implementations Grant Likely
2011-12-12 22:02 ` [RFC v2 3/9] of: Add of_property_match_string() to find index into a string list Grant Likely
2011-12-12 22:02 ` [RFC v2 4/9] of: add clock providers Grant Likely
2011-12-12 23:29 ` Jamie Iles
2011-12-13 17:54 ` Grant Likely
2011-12-13 18:01 ` Rob Herring
2011-12-13 18:03 ` Grant Likely
2011-12-15 13:51 ` Shawn Guo [this message]
2011-12-15 14:23 ` Rob Herring
2011-12-15 15:13 ` Shawn Guo
2011-12-15 17:37 ` Grant Likely
2012-01-10 21:33 ` Jamie Iles
2012-01-12 4:46 ` Grant Likely
2012-01-12 10:07 ` Jamie Iles
2012-01-12 18:44 ` Turquette, Mike
2012-01-12 19:16 ` Grant Likely
2012-01-13 12:47 ` Shawn Guo
2012-01-14 4:30 ` Turquette, Mike
2012-01-14 5:40 ` Shawn Guo
2012-01-13 13:50 ` Shawn Guo
2012-01-13 14:05 ` Rob Herring
2012-01-13 14:38 ` Shawn Guo
2012-01-17 20:44 ` Stephen Warren
2012-01-17 22:47 ` Grant Likely
2012-01-17 23:37 ` Turquette, Mike
2012-01-17 23:49 ` Grant Likely
2012-01-18 0:05 ` Stephen Warren
2011-12-12 22:02 ` [RFC v2 5/9] dt/clock: Add handling for fixed clocks and a clock node setup iterator Grant Likely
2011-12-15 15:19 ` Shawn Guo
2011-12-12 22:02 ` [RFC v2 6/9] arm/dt: add devicetree support to sp804 timer support Grant Likely
2011-12-12 23:54 ` Rob Herring
2011-12-12 22:02 ` [RFC v2 7/9] arm/dt: Common plat-versatile support for icst and sp804 based system clocks Grant Likely
2012-01-17 21:05 ` Stephen Warren
2012-01-17 22:02 ` Rob Herring
2012-01-17 22:59 ` Grant Likely
2011-12-12 22:02 ` [RFC v2 8/9] dt/arm: versatile add clock parsing Grant Likely
2011-12-12 22:02 ` [RFC v2 9/9] arm/highbank: Use clock binding common support code Grant Likely
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