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

[Simon Glass]

Hi Sean,

On Sun, 24 Oct 2021 at 18:13, Sean Anderson <seanga2 at gmail.com> wrote:
>
> On 10/14/21 10:19 PM, Simon Glass wrote:
> > 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.
>
> Can't we have them loudly fail instead?
>

That is how it works today, as I understand it. But some boards want
the defaults to be there but not to implement them in U-Boot. This
seems fair enough to me. Perhaps we could add something to each node
instead, to disable it?

Regards,
Simon

> --Sean