Re: [PATCH v4 3/4] dt-bindings: net: xilinx_axienet: add pcs-handle attribute

On Mon, 2022-03-21 at 15:42 +0000, Radhey Shyam Pandey wrote:

quoted

-----Original Message-----
From: Andy Chiu <redacted>
Sent: Monday, March 21, 2022 8:55 PM
To: Radhey Shyam Pandey <redacted>; robert.hancock@calian.com;
Michal Simek [off-list ref]
Cc: davem@davemloft.net; kuba@kernel.org; pabeni@redhat.com;
robh+dt@kernel.org; linux@armlinux.org.uk; andrew@lunn.ch;
netdev@vger.kernel.org; devicetree@vger.kernel.org; Andy Chiu
[off-list ref]; Greentime Hu [off-list ref]
Subject: [PATCH v4 3/4] dt-bindings: net: xilinx_axienet: add pcs-handle
attribute

Document the new pcs-handle attribute to support connecting to an external
PHY in SGMII or 1000Base-X modes through the internal PCS/PMA PHY.

Signed-off-by: Andy Chiu <redacted>
Reviewed-by: Greentime Hu <greentime.hu@sifive.com>
---
 Documentation/devicetree/bindings/net/xilinx_axienet.txt | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/net/xilinx_axienet.txt

b/Documentation/devicetree/bindings/net/xilinx_axienet.txt
index b8e4894bc634..ba720a2ea5fc 100644

--- a/Documentation/devicetree/bindings/net/xilinx_axienet.txt
+++ b/Documentation/devicetree/bindings/net/xilinx_axienet.txt

@@ -26,7 +26,8 @@ Required properties:
 		  specified, the TX/RX DMA interrupts should be on that node
 		  instead, and only the Ethernet core interrupt is optionally
 		  specified here.
-- phy-handle	: Should point to the external phy device.
+- phy-handle	: Should point to the external phy device if exists.

Pointing
+		  this to the PCS/PMA PHY is deprecated and should be
avoided.
 		  See ethernet.txt file in the same directory.
 - xlnx,rxmem	: Set to allocated memory buffer for Rx/Tx in the
hardware

@@ -68,6 +69,11 @@ Optional properties:
 		  required through the core's MDIO interface (i.e. always,
 		  unless the PHY is accessed through a different bus).

+ - pcs-handle: 	  Phandle to the internal PCS/PMA PHY in SGMII or

1000Base-X
+		  modes, where "pcs-handle" should be preferably used to
point
+		  to the PCS/PMA PHY, and "phy-handle" should point to an
+		  external PHY if exists.

I would like to have Rob feedback on this pcs-handle DT property.

The use case is generic i.e. require separate handle to internal SGMII
and external Phy so would prefer this new DT convention is 
standardized or we discuss possible approaches on how to handle
both phys and not add it as vendor specific property in the first 
place.

The pcs-handle property is currently used in the Freescale dpaa2 driver, so
there's some precedent for it. But I suppose if it's intended to be a standard
mechanism it should be documented more globally?

quoted

+
 Example:
 	axi_ethernet_eth: ethernet@40c00000 {
 		compatible = "xlnx,axi-ethernet-1.00.a";
--
2.34.1