linux-kernel - Re: [STLinux Kernel] [PATCH 02/11] drivers: clk: st: Add clock propagation for audio clocks

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Message-ID: <5746F486.602@st.com>
Date:	Thu, 26 May 2016 15:05:10 +0200
From:	loic pallardy <loic.pallardy@...com>
To:	Rob Herring <robh@...nel.org>,
	Gabriel Fernandez <gabriel.fernandez@...aro.org>
CC:	Mark Rutland <mark.rutland@....com>,
	"kernel@...inux.com" <kernel@...inux.com>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Michael Turquette <mturquette@...libre.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrzej Hajda <a.hajda@...sung.com>,
	linux-clk <linux-clk@...r.kernel.org>,
	Benjamin GAIGNARD <benjamin.gaignard@...com>,
	Olivier Bideau <olivier.bideau@...com>,
	Russell King <linux@...linux.org.uk>,
	Thierry Reding <treding@...dia.com>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Vincent ABRIOU <vincent.abriou@...com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Srinivas Kandagatla <srinivas.kandagatla@...il.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Kumar Gala <galak@...eaurora.org>,
	Dinh Nguyen <dinguyen@...nsource.altera.com>
Subject: Re: [STLinux Kernel] [PATCH 02/11] drivers: clk: st: Add clock
 propagation for audio clocks

On 05/26/2016 02:46 PM, Rob Herring wrote:
> On Thu, May 26, 2016 at 4:49 AM, Gabriel Fernandez
> <gabriel.fernandez@...aro.org> wrote:
>> On 25 May 2016 at 19:24, Rob Herring <robh@...nel.org> wrote:
>>>
>>> On Wed, May 18, 2016 at 10:41:23AM +0200, Gabriel Fernandez wrote:
>>>> This patch allows fine tuning of the quads FS for audio clocks
>>>> accuracy.
>>>>
>>>> Signed-off-by: Olivier Bideau <olivier.bideau@...com>
>>>> Signed-off-by: Gabriel Fernandez <gabriel.fernandez@...aro.org>
>>>> ---
>>>>   .../devicetree/bindings/clock/st/st,flexgen.txt    |  1 +
>>>>   drivers/clk/st/clk-flexgen.c                       | 24 ++++++++++++++++++++++
>>>>   2 files changed, 25 insertions(+)
>>>>
>>>> diff --git a/Documentation/devicetree/bindings/clock/st/st,flexgen.txt b/Documentation/devicetree/bindings/clock/st/st,flexgen.txt
>>>> index b7ee5c7..15b33c7 100644
>>>> --- a/Documentation/devicetree/bindings/clock/st/st,flexgen.txt
>>>> +++ b/Documentation/devicetree/bindings/clock/st/st,flexgen.txt
>>>> @@ -60,6 +60,7 @@ This binding uses the common clock binding[2].
>>>>   Required properties:
>>>>   - compatible : shall be:
>>>>     "st,flexgen"
>>>> +  "st,stih407-clkgend0", "st,flexgen" (enable clock propagation on parent)
>>>
>>> What do "d0" and "d2" refer to?
>>>
>>> This seems to indicate you have too much clock detail in the DT (with
>>> individual clocks described) or not enough with genericish compatible
>>> strings. What happens for the mext clock you need to adjust the flags
>>> on? You should be able to make these adjustments without DT updates.
>>> Perhaps you need a wider fixing of clock compatible strings.
>>>
>>> Rob
>>
>> Sorry i sent my response in html...
>>
>> Hi Rob,
>>
>> Thanks for reviewing.
>>
>> Can i remove
>> "
>> st,stih407-clkgend0" & "
>> st,stih407-clkgend2" compatible strings and add proprieties instead ?
>> I only need to activate 2 features and then we can keep generic
>> compatible strings.
>
Hi Rob,
> That is no different and suffers the same point I raised. It requires
> updating the DT for any clock configuration change or enhancement.
>
Agree with you, DT update is needed as soon as a clock configuration 
should be changed. This is due to STiH clock driver design based on DT 
description of SoC clock tree.

This clock driver was accepted 2 years ago. At the time being there was 
discussion about clock tree description location: driver or DT.
Bad choice was done for this driver...

If we decide to redesign STiH clock driver using in-driver clock tree 
description, this will modify STiH clock DT nodes description and so 
break DT backward compatibility.

What's from your pov the best option?

Regards,
Loic

> Rob
>
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> Kernel mailing list
> Kernel@...inux.com
> http://www.stlinux.com/mailman/listinfo/kernel
>

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