Re: [PATCH v5 2/5] dt-bindings: net: wireless: brcm4329-fmac: add clock description for AP6275P

[Arend Van Spriel]

On July 30, 2024 12:18:20 PM Krzysztof Kozlowski <krzk@xxxxxxxxxx> wrote:

> On 30/07/2024 11:52, Arend Van Spriel wrote:
> > On July 30, 2024 11:01:43 AM Krzysztof Kozlowski <krzk@xxxxxxxxxx> wrote:
> >
> > > On 30/07/2024 08:37, Arend Van Spriel wrote:
> > > > + Linus W
> > > >
> > > > On July 30, 2024 5:31:15 AM Jacobe Zang <jacobe.zang@xxxxxxxxxx> wrote:
> > > >
> > > > > Not only AP6275P Wi-Fi device but also all Broadcom wireless devices allow
> > > > > external low power clock input. In DTS the clock as an optional choice in
> > > > > the absence of an internal clock.
> > > > >
> > > > > Reviewed-by: Arend van Spriel <arend.vanspriel@xxxxxxxxxxxx>
> > > > > Signed-off-by: Jacobe Zang <jacobe.zang@xxxxxxxxxx>
> > > > > ---
> > > > > .../bindings/net/wireless/brcm,bcm4329-fmac.yaml          | 8 ++++++++
> > > > > 1 file changed, 8 insertions(+)
> > > > >
> > > > > diff --git
> > > > > a/Documentation/devicetree/bindings/net/wireless/brcm,bcm4329-fmac.yaml
> > > > > b/Documentation/devicetree/bindings/net/wireless/brcm,bcm4329-fmac.yaml
> > > > > index 2c2093c77ec9a..a3607d55ef367 100644
> > > > > --- a/Documentation/devicetree/bindings/net/wireless/brcm,bcm4329-fmac.yaml
> > > > > +++ b/Documentation/devicetree/bindings/net/wireless/brcm,bcm4329-fmac.yaml
> > > > > @@ -122,6 +122,14 @@ properties:
> > > > > NVRAM. This would normally be filled in by the bootloader from platform
> > > > > configuration data.
> > > > >
> > > > > +  clocks:
> > > > > +    items:
> > > > > +      - description: External Low Power Clock input (32.768KHz)
> > > > > +
> > > > > +  clock-names:
> > > > > +    items:
> > > > > +      - const: lpo
> > > > > +
> > > >
> > > > We still have an issue that this clock input is also present in the
> > > > bindings specification broadcom-bluetooth.yaml (not in bluetooth
> > > > subfolder). This clock is actually a chip resource. What happens if both
> > > > are defined and both wifi and bt drivers try to enable this clock? Can this
> > > > be expressed in yaml or can we only put a textual warning in the property
> > > > descriptions?
> > >
> > > Just like all clocks, what would happen? It will be enabled.
> >
> > Oh, wow! Cool stuff. But seriously is it not a problem to have two entities
> > controlling one and the same clock? Is this use-case taken into account by
> > the clock framework?
>
> Yes, it is handled correctly. That's a basic use-case, handled by CCF
> since some years (~12?). Anyway, whatever OS is doing (or not doing)
> with the clocks is independent of the bindings here. The question is

Agree. Probably the bindings would not be the place to document this if it 
would be an issue.

> about hardware - does this node, which represents PCI interface of the
> chip, has/uses the clocks.

The schematics I found for the wifi module and the khadas edge platform 
show these are indeed wired to the chip.

Regards,
Arend

> Best regards,
> Krzysztof