[PATCH] clk: introduce u-boot,ignore-clk-defaults

[Simon Glass]

Hi Peng, Sean,

On Thu, 14 Oct 2021 at 19:17, Peng Fan <peng.fan at nxp.com> wrote:
>
> > Subject: Re: [PATCH] clk: introduce u-boot,ignore-clk-defaults
> >
> >
> > On 10/13/21 5:37 AM, Peng Fan (OSS) wrote:
> > > From: Peng Fan <peng.fan at nxp.com>
> > >
> > > Current code has a force clk_set_defaults in multiple stages, U-Boot
> > > reuse the same device tree and Linux Kernel device tree, but we not
> > > register all the clks as Linux Kernel, so clk_set_defaults will fail
> > > and cause the clk provider registeration fail.
> > >
> > > So introduce a new property to ignore the default settings which could
> > > be used by any node that wanna ignore default settings.
> > >
> > > Signed-off-by: Peng Fan <peng.fan at nxp.com>
> > > ---
> > >   doc/device-tree-bindings/device.txt | 3 +++
> > >   drivers/clk/clk-uclass.c            | 3 +++
> > >   2 files changed, 6 insertions(+)
> > >
> > > diff --git a/doc/device-tree-bindings/device.txt
> > > b/doc/device-tree-bindings/device.txt
> > > index 73ce2a3b5b..fe34ced268 100644
> > > --- a/doc/device-tree-bindings/device.txt
> > > +++ b/doc/device-tree-bindings/device.txt
> > > @@ -28,6 +28,9 @@ the acpi,compatible property.
> > >       Linux will only load the driver if the device can be detected (e.g. on
> > I2C
> > >       bus). Note that this is an out-of-tree Linux feature.
> > >
> > > +Common device bindings that could be shared listed below:
> > > + - u-boot,ignore-clk-defaults : ignore the assigned-clock-parents
> > > +   and assigned-clock-rates for a device that has the property.
> > >
> > >   Example
> > >   -------
> > > diff --git a/drivers/clk/clk-uclass.c b/drivers/clk/clk-uclass.c index
> > > 493018b33e..6bf3179e7b 100644
> > > --- a/drivers/clk/clk-uclass.c
> > > +++ b/drivers/clk/clk-uclass.c
> > > @@ -376,6 +376,9 @@ int clk_set_defaults(struct udevice *dev, enum
> > clk_defaults_stage stage)
> > >     if (!dev_has_ofnode(dev))
> > >             return 0;
> > >
> > > +   if (ofnode_get_property(dev_ofnode(dev), "u-boot,ignore-clk-defaults",
> > NULL))
> > > +           return 0;
> > > +
> > >     /*
> > >      * To avoid setting defaults twice, don't set them before relocation.
> > >      * However, still set them for SPL. And still set them if
> > > explicitly
> > >
> >
> > Why not just have the property ignore errors?
>
> I think the force err return was done by Simon?
>
> >
> > In the long term, it may be better to standardize that e.g. ENOENT means that
> > the clock doesn't exist. That way we can skip setting the defaults.
> > ENOSYS should probably be treated the same way (warn, but don't fail).
>
> I am not sure whether people expect force error for ENOENT/ENOSYS in U-Boot.
> For i.MX, I not expect force error.

Yes that is me, indeed. It's just that we should not silently ignore
errors. If we know the clock is optional, then the driver that knows
that can handle it. But if we start having things quietly fail,
debugging becomes a pain.

Regards,
Simon