Re: [PATCH net-next v3 03/10] dt-bindings: net: cdns,macb: replace cdns,refclk-ext with cdns,refclk-source

On Wed, Mar 11, 2026 at 07:10:09PM +0100, Krzysztof Kozlowski wrote:

On 11/03/2026 19:08, Conor Dooley wrote:

quoted

On Wed, Mar 11, 2026 at 08:00:54AM +0100, Krzysztof Kozlowski wrote:

quoted

On Tue, Mar 10, 2026 at 05:17:10PM +0000, Conor Dooley wrote:

quoted

From: Conor Dooley <conor.dooley@microchip.com>

Ryan added cdns,refclk-ext with the intent of decoupling the source of
the reference clock on sama7g5 (and related platforms) from the
compatible. Unfortunately, the default for sama7g5-emac is an external
reference clock, so this property had no effect there, so that
compatibility with older devicetrees is preserved.
Replace cdns,refclk-ext with one that supports both default states and
therefore is usable for sama7g5-emac.

For now, limit it to only the platforms that have USRIO controlled
reference clock selection, but this could be generalised in the future.

Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
---
 .../devicetree/bindings/net/cdns,macb.yaml    | 39 ++++++++++++++++---
 1 file changed, 34 insertions(+), 5 deletions(-)

diff --git a/Documentation/devicetree/bindings/net/cdns,macb.yaml b/Documentation/devicetree/bindings/net/cdns,macb.yaml
index cb14c35ba9969..a492357570edd 100644
--- a/Documentation/devicetree/bindings/net/cdns,macb.yaml
+++ b/Documentation/devicetree/bindings/net/cdns,macb.yaml

@@ -120,12 +120,14 @@ properties:
   power-domains:
     maxItems: 1
 
-  cdns,refclk-ext:
-    type: boolean

This is already an implemented ABI, so you cannot drop it even if some
devices works fine on default. Instead please deprecate it and keep
drivers backwards compatible for whoever is using it.

The driver still will support it for those devices, but I don't see any
value in keeping the property about, even deprecated, when it doesn't
work properly. If you insist that it be kept and marked deprecated, it

There cannot be an undocumented ABI, so if driver has it, it must stay
in the bindings.

Right that's something I should have considered.
I'll keep it so.

quoted

needs conditional rules to only permit it on devices that it actually
does something. I'm surprised you even considered that I would drop
support for it from the driver!

Commit msg suggested it is no-op, thus could be dropped without having
impact?

Nah, it's not an NOP. Commit message maybe reads that way because I was
trying to avoid mentioning the driver implementation details. I think I
could do a better job talking about sama7g5-emac versus sama7g5-gem in
the commit message, which would show that the current property has a use
case, just not as broad as it was intended to be.

The existing property was added along with a driver change that modified
sama7g5-emac which had a default of external to default to internal instead,
and the property could be used to switch to external. sama7g5-gem had a
default of internal, so this change was done to make things uniform and
allow a single property to work for both devices.
That driver change was reverted to maintain backwards compatibility, so
the property became useless on sama7g5-emac, and there's currently no
way to make that device use an internal reference.

What I am doing here is probably what cdns,refclk-ext should have been
originally, but when the driver's defaults got reverted the whole series
probably should have been reverted so that Ryan could try again with a
new approach. Instead, the property went into a release but only works
on sama7g5-gem.