Re: [net-next PATCH RFC v3 1/8] dt-bindings: net: document ethernet PHY package nodes
From: Sergey Ryazanov
Date: Wed Jan 17 2024 - 14:39:46 EST
Hi Christian,
On 17.01.2024 02:36, Christian Marangi wrote:
On Sun, Jan 07, 2024 at 11:49:12PM +0200, Sergey Ryazanov wrote:
Hi Christian,
On 07.01.2024 20:30, Christian Marangi wrote:
On Sun, Jan 07, 2024 at 08:00:33PM +0200, Sergey Ryazanov wrote:
On 26.11.2023 03:53, Christian Marangi wrote:
Document ethernet PHY package nodes used to describe PHY shipped in
bundle of 4-5 PHY. The special node describe a container of PHY that
share common properties. This is a generic schema and PHY package
should create specialized version with the required additional shared
properties.
Example are PHY package that have some regs only in one PHY of the
package and will affect every other PHY in the package, for example
related to PHY interface mode calibration or global PHY mode selection.
The PHY package node MUST declare the base address used by the PHY driver
for global configuration by calculating the offsets of the global PHY
based on the base address of the PHY package and declare the
"ethrnet-phy-package" compatible.
Each reg of the PHY defined in the PHY package node is absolute and will
reference the real address of the PHY on the bus.
Signed-off-by: Christian Marangi <ansuelsmth@xxxxxxxxx>
---
.../bindings/net/ethernet-phy-package.yaml | 75 +++++++++++++++++++
1 file changed, 75 insertions(+)
create mode 100644 Documentation/devicetree/bindings/net/ethernet-phy-package.yaml
diff --git a/Documentation/devicetree/bindings/net/ethernet-phy-package.yaml b/Documentation/devicetree/bindings/net/ethernet-phy-package.yaml
new file mode 100644
index 000000000000..244d4bc29164
--- /dev/null
+++ b/Documentation/devicetree/bindings/net/ethernet-phy-package.yaml
@@ -0,0 +1,75 @@
+# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/net/ethernet-phy-package.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Ethernet PHY Package Common Properties
+
+maintainers:
+ - Christian Marangi <ansuelsmth@xxxxxxxxx>
+
+description:
+ This schema describe PHY package as simple container for
+ a bundle of PHYs that share the same properties and
+ contains the PHYs of the package themself.
+
+ Each reg of the PHYs defined in the PHY package node is
+ absolute and describe the real address of the PHY on the bus.
+
+properties:
+ $nodename:
+ pattern: "^ethernet-phy-package(@[a-f0-9]+)?$"
+
+ compatible:
+ const: ethernet-phy-package
+
+ reg:
+ minimum: 0
+ maximum: 31
+ description:
+ The base ID number for the PHY package.
+ Commonly the ID of the first PHY in the PHY package.
+
+ Some PHY in the PHY package might be not defined but
+ still exist on the device (just not attached to anything).
+ The reg defined in the PHY package node might differ and
+ the related PHY might be not defined.
+
+ '#address-cells':
+ const: 1
+
+ '#size-cells':
+ const: 0
+
+patternProperties:
+ ^ethernet-phy(@[a-f0-9]+)?$:
+ $ref: ethernet-phy.yaml#
+
+required:
+ - compatible
+ - reg
+
+additionalProperties: true
+
+examples:
+ - |
+ mdio {
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ ethernet-phy-package@16 {
+ #address-cells = <1>;
+ #size-cells = <0>;
+ compatible = "ethernet-phy-package";
+ reg = <0x16>;
+
+ ethernet-phy@16 {
+ reg = <0x16>;
+ };
+
+ phy4: ethernet-phy@1a {
+ reg = <0x1a>;
+ };
+ };
+ };
So, we ended up on a design where we use the predefined compatible string
'ethernet-phy-package' to recognize a phy package inside the
of_mdiobus_register() function. During the V1 discussion, Vladimir came up
with the idea of 'ranges' property usage [1]. Can we use 'ranges' to
recognize a phy package in of_mdiobus_register()? IMHO this will give us a
clear DT solution. I mean 'ranges' clearly indicates that child nodes are in
the same address range as the parent node. Also we can list all child
addresses in 'reg' to mark them occupied.
mdio {
...
ethernet-phy-package@16 {
compatible = "qcom,qca8075";
reg = <0x16>, <0x17>, <0x18>, <0x19>, <0x1a>;
ranges;
...
ethernet-phy@16 {
reg = <0x16>;
};
ethernet-phy@1a {
reg = <0x1a>;
};
};
};
Did you find some issues with the 'ranges' conception?
Nope it's ok but it might pose some confusion with the idea that the
very first element MUST be THE STARTING ADDR of the PHY package. (people
might think that it's just the list of the PHYs in the package and
remove the hardware unconnected ones... but that would be fault of who
write the DT anyway.)
Make sense. I do not insist on addresses listing. Mainly I'm thinking of a
proper way to show that child nodes are accessible directly on the parent
bus, and introducing the special compatibility string, while we already have
the 'ranges' property.
But it's good to know Rob's opinion on whether it is conceptually right to
use 'ranges' here.
I wonder if something like this might make sense... Thing is that with
the ranges property we would have the define the address in the PHY
Package node as offsets...
An example would be
mdio {
#address-cells = <1>;
#size-cells = <0>;
ethernet-phy-package@10 {
#address-cells = <1>;
#size-cells = <0>;
compatible = "qcom,qca807x-package";
reg = <0x10>;
ranges = <0x0 0x10 0x5>;
qcom,package-mode = "qsgmii";
ethernet-phy@0 {
reg = <0>;
leds {
...
With a PHY Package at 0x10, that span 5 address and the child starts at
0x0 offset.
This way we would be very precise on describing the amount of address
used by the PHY Package without having to define the PHY not actually
connected.
PHY needs to be at an offset to make sense of the ranges first element
property (0x0). With a non offset way we would have to have something
like
ranges = <0x10 0x10 0x5>;
With the child and tha parent always matching.
(this is easy to handle in the parsing and probe as we will just
calculate the real address based on the base address of the PHY package
+ offset)
On one hand it makes sense and looks useful for software development. On
another, it looks like a violation of the main DT designing rule, when
DT should be used to describe that hardware properties, which can not be
learnt from other sources.
As far as I understand this specific chip, each of embedded PHYs has its
own MDIO bus address and not an offset from a main common address.
Correct me please, if I am got it wrong.
I hope Rob can give more feedback about this, is this what you were
thinking with the usage of ranges property?
(this has also the bonus point of introducing some validation in the PHY
core code to make sure the right amount of PHY are defined in the
package by checking if the number of PHY doesn't exceed the value set in
ranges.)
Yep, I am also would like to hear some clarification from Rob regarding
acceptable 'range' property usage and may be some advice on how to
specify the size of occupied addresses. Rob?
--
Sergey