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

[loic pallardy]

On 05/26/2016 02:46 PM, Rob Herring wrote:
> On Thu, May 26, 2016 at 4:49 AM, Gabriel Fernandez
> <gabriel.fernandez@xxxxxxxxxx> wrote:
> > On 25 May 2016 at 19:24, Rob Herring <robh@xxxxxxxxxx> 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@xxxxxx>
> > > > Signed-off-by: Gabriel Fernandez <gabriel.fernandez@xxxxxxxxxx>
> > > > ---
> > > >   .../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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