[U-Boot] [i.MX8MM+CCF 03/41] clk: introduce clk_dev_binded

[Lukasz Majewski <lukma@denx.de>]

On Tue, 7 May 2019 13:22:24 +0000
Peng Fan <peng.fan@nxp.com> wrote:

> > Subject: Re: [i.MX8MM+CCF 03/41] clk: introduce clk_dev_binded
> > 
> > On Tue, 30 Apr 2019 10:17:40 +0000
> > Peng Fan <peng.fan@nxp.com> wrote:
> >   
> > > When support Clock Common Framework, U-Boot use dev for clk tree
> > > information, there is no clk->parent.  
> > 
> > There is a function in clk uclass named:
> > clk_get_parent() to provide parent of the clock.
> >   
> > > When
> > > support composite clk, it contains mux/gate/divider, but the
> > > mux/gate/divider is not binded with device.  
> > 
> > There is a binding:
> > struct clk_pllv3 {
> > 	struct clk	clk;
> > 	...
> > };
> > 
> > The clk.dev points to corresponding device.
> > 
> > In the opposite direction we do have dev->driver_data, which points
> > to struct clk embedded in for example struct clk_pllv3.
> > (as struct clk_pllv3 and struct clk share the same address it is up
> > to us to cast it properly).
> > 
> > I've written my thoughts and considerations about using
> > dev->private and dev->driver_data in the patch cover letter [1]
> > 
> >   
> > > So we could not use dev_get_driver_data to get the correct
> > > clk_mux/gate/divider.  
> > 
> > Maybe I've overlooked something, but dev_get_driver_data() shall
> > provide correct reference to udevice.  
> 
> A composite clk contains a mux/gate/divider clk. Only the composite
> clk needs to binded with a udevice.

So, if I understood correctly we do need to have another reference to
udevice (or clock)?

Please correct my understanding:

- Composite clock would use clk->dev (to have pointer to struct udevice)
  and dev->driver_data to have pointer to clk.

- Then we use udevice flag DM_FLAG_BOUND to indicate if this device has
  other udevices (i.e. clk) bound.

- If it has bounded device then we use dev->driver_data to get it's
  struct clk (or clock IP - like mux). If not, then we just use this
  clk.

Considering the above - the commit message needs detailed explanation
of the "binding" concept.

> The mux/gate/divider inside a
> composite clk should not bind a device, because they needs to be
> hidden from dm tree or clk dumps.
> 
> If bind the mux/gate/divider insides a composite clk, that will be
> mess.

But the composite clock itself would be printed in 'dm tree' ?

If yes, maybe we can add some kind of indication that it is a
"container" and that it has some clocks "binded" ?

> The reason to introduce composite clk is to make clk tree
> cleaner/simplier.

Ok. No problem with this.

> 
> Regards,
> Peng.
> 
> >   
> > > So add clk_dev_binded to let
> > > choose the correct method.
> > >  
> > 
> > [1] - http://patchwork.ozlabs.org/cover/1090669/
> >   
> > > Signed-off-by: Peng Fan <peng.fan@nxp.com>
> > > ---
> > >  drivers/clk/clk.c | 8 ++++++++
> > >  include/clk.h     | 9 +++++++++
> > >  2 files changed, 17 insertions(+)
> > >
> > > diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c index
> > > 0a0fffb50b..025bb99ecc 100644
> > > --- a/drivers/clk/clk.c
> > > +++ b/drivers/clk/clk.c
> > > @@ -54,3 +54,11 @@ const char *clk_hw_get_name(const struct clk
> > > *hw) {
> > >  	return hw->dev->name;
> > >  }
> > > +
> > > +bool clk_dev_binded(struct clk *clk)
> > > +{
> > > +	if (clk->dev && (clk->dev->flags & DM_FLAG_BOUND))
> > > +		return true;
> > > +
> > > +	return false;
> > > +}
> > > diff --git a/include/clk.h b/include/clk.h index
> > > a4ecca9fbc..8199119d01 100644
> > > --- a/include/clk.h
> > > +++ b/include/clk.h
> > > @@ -337,4 +337,13 @@ static inline bool clk_valid(struct clk *clk)
> > >   * @return zero on success, or -ENOENT on error
> > >   */
> > >  int clk_get_by_id(ulong id, struct clk **clkp);
> > > +
> > > +/**
> > > + * clk_dev_binded() - Check whether the clk has a device binded
> > > + *
> > > + * @clk		A pointer to the clk
> > > + *
> > > + * @return true on binded, or false on no  */ bool
> > > +clk_dev_binded(struct clk *clk);
> > >  #endif  
> > 
> > 
> > 
> > 
> > Best regards,
> > 
> > Lukasz Majewski
> > 
> > --
> > 
> > DENX Software Engineering GmbH,      Managing Director: Wolfgang
> > Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell,
> > Germany Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email:
> > lukma at denx.de  




Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma at denx.de
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