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Date: Mon, 14 Sep 2015 09:58:46 +0200
From: Boris Brezillon <boris.brezillon@free-electrons.com>
To: Harini Katakam <harinikatakamlinux@gmail.com>
Cc: =?UTF-8?B?U8O2cmVu?= Brinkmann <soren.brinkmann@xilinx.com>,
        Harini Katakam <harini.katakam@xilinx.com>,
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        Rob Herring <robh+dt@kernel.org>, Pawel Moll <pawel.moll@arm.com>,
        Mark Rutland <mark.rutland@arm.com>,
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        Punnaiah Choudary Kalluri <punnaia@xilinx.com>,
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Subject: Re: [RFC PATCH 3/3] devicetree: macb: Add optional property tsu-clk
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Hi Harini,

On Mon, 14 Sep 2015 09:39:05 +0530
Harini Katakam <harinikatakamlinux@gmail.com> wrote:

> On Fri, Sep 11, 2015 at 10:22 PM, Sören Brinkmann
> <soren.brinkmann@xilinx.com> wrote:
> > Hi Harini,
> >
> > On Fri, 2015-09-11 at 01:27PM +0530, Harini Katakam wrote:
> >> Add TSU clock frequency to be used for 1588 support in macb driver.
> >>
> >> Signed-off-by: Harini Katakam <harinik@xilinx.com>
> >> ---
> >>  Documentation/devicetree/bindings/net/macb.txt |    3 +++
> >>  1 file changed, 3 insertions(+)
> >>
> >> diff --git a/Documentation/devicetree/bindings/net/macb.txt b/Documentation/devicetree/bindings/net/macb.txt
> >> index b5d7976..f7c0ea8 100644
> >> --- a/Documentation/devicetree/bindings/net/macb.txt
> >> +++ b/Documentation/devicetree/bindings/net/macb.txt
> >> @@ -19,6 +19,9 @@ Required properties:
> >>       Optional elements: 'tx_clk'
> >>  - clocks: Phandles to input clocks.
> >>
> >> +Optional properties:
> >> +- tsu-clk: Time stamp unit clock frequency used.
> >
> > Why are we not using the CCF and a clk_get_rate() in the driver?
> >
> 
> If the clock source was only internal, we could use this
> approach as usual. But TSU clock can be configured to
> come from an external clock source or internal.

How about declaring a fixed-rate clk [1] if it comes from an external
clk, and using a clk driver for the internal clk case?
This way you'll be able to use the clk API (including the
clk_get_rate() function) instead of introducing a new way to retrieve a
clk frequency.

Best Regards,

Boris

[1]http://lxr.free-electrons.com/source/Documentation/devicetree/bindings/clock/fixed-clock.txt

-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com