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Re: [RFC PATCH 3/3] devicetree: macb: Add optional property tsu-clk

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  Re: [RFC PATCH 3/3] devicetree: macb: Add optional property tsu-clk Harini Katakam <harinikatakamlinux@gmail.com> - 2015-09-14 06:10 +0200
    Re: [RFC PATCH 3/3] devicetree: macb: Add optional property tsu-clk Boris Brezillon <boris.brezillon@free-electrons.com> - 2015-09-14 10:00 +0200
      Re: [RFC PATCH 3/3] devicetree: macb: Add optional property tsu-clk Harini Katakam <harinikatakamlinux@gmail.com> - 2015-09-14 19:40 +0200

#1223829 — Re: [RFC PATCH 3/3] devicetree: macb: Add optional property tsu-clk

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.

Regards,
Harini
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#1223896

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
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#1224363

Hi Soren/Boris,

On Mon, Sep 14, 2015 at 8:14 PM, Sören Brinkmann
<soren.brinkmann@xilinx.com> wrote:
> On Mon, 2015-09-14 at 09:58AM +0200, Boris Brezillon wrote:
>> 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.
>
> Right. Also, Zynq does already support external clock inputs (actually,
> every clock originates from some external clock/oscillator at some
> point). Maybe that code needs some additions to handle the TSU clock
> too. But either way, I can't see why a clock cannot be modeled using the
> CCF.

Ok, I'm going to try this.

Regards,
Harini
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