[PATCH devicetree v3] dt-bindings: phy: Add `tx-p2p-microvolt` property binding

[Marek Behún]

Common PHYs and network PCSes often have the possibility to specify
peak-to-peak voltage on the differential pair - the default voltage
sometimes needs to be changed for a particular board.

Add properties `tx-p2p-microvolt` and `tx-p2p-microvolt-names` for this
purpose. The second property is needed to specify the mode for the
corresponding voltage in the `tx-p2p-microvolt` property, if the voltage
is to be used only for speficic mode. More voltage-mode pairs can be
specified.

Example usage with only one voltage (it will be used for all supported
PHY modes, the `tx-p2p-microvolt-names` property is not needed in this
case):

  tx-p2p-microvolt = <915000>;

Example usage with voltages for multiple modes:

  tx-p2p-microvolt = <915000>, <1100000>, <1200000>;
  tx-p2p-microvolt-names = "2500base-x", "usb", "pcie";

Add these properties into a separate file phy/transmit-amplitude.yaml,
which should be referenced by any binding that uses it.

Signed-off-by: Marek Behún <kabel at kernel.org>
---
Change since v2:
- removed 'select:' as requested by Rob. Instead the schema should be
  referenced by any binding that uses it. This also fixed indentation
  warnings from Rob's bot, since they warned about lines in the select
  statement
---
 .../bindings/phy/transmit-amplitude.yaml      | 103 ++++++++++++++++++
 1 file changed, 103 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/phy/transmit-amplitude.yaml

diff --git a/Documentation/devicetree/bindings/phy/transmit-amplitude.yaml b/Documentation/devicetree/bindings/phy/transmit-amplitude.yaml
new file mode 100644
index 000000000000..51492fe738ec
--- /dev/null
+++ b/Documentation/devicetree/bindings/phy/transmit-amplitude.yaml
@@ -0,0 +1,103 @@
+# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/phy/transmit-amplitude.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Common PHY and network PCS transmit amplitude property binding
+
+description:
+  Binding describing the peak-to-peak transmit amplitude for common PHYs
+  and network PCSes.
+
+maintainers:
+  - Marek Behún <kabel at kernel.org>
+
+properties:
+  tx-p2p-microvolt:
+    description:
+      Transmit amplitude voltages in microvolts, peak-to-peak. If this property
+      contains multiple values for various PHY modes, the
+      'tx-p2p-microvolt-names' property must be provided and contain
+      corresponding mode names.
+
+  tx-p2p-microvolt-names:
+    description: |
+      Names of the modes corresponding to voltages in the 'tx-p2p-microvolt'
+      property. Required only if multiple voltages are provided.
+
+      If a value of 'default' is provided, the system should use it for any PHY
+      mode that is otherwise not defined here. If 'default' is not provided, the
+      system should use manufacturer default value.
+    minItems: 1
+    maxItems: 16
+    items:
+      enum:
+        - default
+
+        # ethernet modes
+        - sgmii
+        - qsgmii
+        - xgmii
+        - 1000base-x
+        - 2500base-x
+        - 5gbase-r
+        - rxaui
+        - xaui
+        - 10gbase-kr
+        - usxgmii
+        - 10gbase-r
+        - 25gbase-r
+
+        # PCIe modes
+        - pcie
+        - pcie1
+        - pcie2
+        - pcie3
+        - pcie4
+        - pcie5
+        - pcie6
+
+        # USB modes
+        - usb
+        - usb-ls
+        - usb-fs
+        - usb-hs
+        - usb-ss
+        - usb-ss+
+        - usb-4
+
+        # storage modes
+        - sata
+        - ufs-hs
+        - ufs-hs-a
+        - ufs-hs-b
+
+        # display modes
+        - lvds
+        - dp
+        - dp-rbr
+        - dp-hbr
+        - dp-hbr2
+        - dp-hbr3
+        - dp-uhbr-10
+        - dp-uhbr-13.5
+        - dp-uhbr-20
+
+        # camera modes
+        - mipi-dphy
+        - mipi-dphy-univ
+        - mipi-dphy-v2.5-univ
+
+dependencies:
+  tx-p2p-microvolt-names: [ tx-p2p-microvolt ]
+
+additionalProperties: true
+
+examples:
+  - |
+    phy: phy {
+      #phy-cells = <1>;
+      tx-p2p-microvolt = <915000>, <1100000>, <1200000>;
+      tx-p2p-microvolt-names = "2500base-x", "usb-hs", "usb-ss";
+    };
-- 
2.34.1