dt-bindings: phy: phy-stm32-usbphyc: add optional phy tuning properties

This patch adds the description of new optional phy tuning properties
for usbphyc phy sub nodes.
Signed-off-by: Amelie Delaunay <amelie.delaunay@foss.st.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211015161427.220784-3-amelie.delaunay@foss.st.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

Documentation/devicetree/bindings/phy/phy-stm32-usbphyc.yaml

@@ -81,6 +81,119 @@ patternProperties:
         properties:
           vbus-supply: true
 
+      # It can be necessary to adjust the PHY settings to compensate parasitics, which can be due
+      # to USB connector/receptacle, routing, ESD protection component,... Here is the list of
+      # all optional parameters to tune the interface of the PHY (HS for High-Speed, FS for Full-
+      # Speed, LS for Low-Speed)
+
+      st,current-boost-microamp:
+        description: Current boosting in uA
+        enum: [ 1000, 2000 ]
+
+      st,no-lsfs-fb-cap:
+        description: Disables the LS/FS feedback capacitor
+        type: boolean
+
+      st,decrease-hs-slew-rate:
+        description: Decreases the HS driver slew rate by 10%
+        type: boolean
+
+      st,tune-hs-dc-level:
+        description: |
+          Tunes the HS driver DC level
+          - <0> normal level
+          - <1> increases the level by 5 to 7 mV
+          - <2> increases the level by 10 to 14 mV
+          - <3> decreases the level by 5 to 7 mV
+        $ref: /schemas/types.yaml#/definitions/uint32
+        minimum: 0
+        maximum: 3
+        default: 0
+
+      st,enable-fs-rftime-tuning:
+        description: Enables the FS rise/fall tuning option
+        type: boolean
+
+      st,enable-hs-rftime-reduction:
+        description: Enables the HS rise/fall reduction feature
+        type: boolean
+
+      st,trim-hs-current:
+        description: |
+          Controls HS driver current trimming for choke compensation
+          - <0> = 18.87 mA target current / nominal + 0%
+          - <1> = 19.165 mA target current / nominal + 1.56%
+          - <2> = 19.46 mA target current / nominal + 3.12%
+          - <3> = 19.755 mA target current / nominal + 4.68%
+          - <4> = 20.05 mA target current / nominal + 6.24%
+          - <5> = 20.345 mA target current / nominal + 7.8%
+          - <6> = 20.64 mA target current / nominal + 9.36%
+          - <7> = 20.935 mA target current / nominal + 10.92%
+          - <8> = 21.23 mA target current / nominal + 12.48%
+          - <9> = 21.525 mA target current / nominal + 14.04%
+          - <10> = 21.82 mA target current / nominal + 15.6%
+          - <11> = 22.115 mA target current / nominal + 17.16%
+          - <12> = 22.458 mA target current / nominal + 19.01%
+          - <13> = 22.755 mA target current / nominal + 20.58%
+          - <14> = 23.052 mA target current / nominal + 22.16%
+          - <15> = 23.348 mA target current / nominal + 23.73%
+        $ref: /schemas/types.yaml#/definitions/uint32
+        minimum: 0
+        maximum: 15
+        default: 0
+
+      st,trim-hs-impedance:
+        description: |
+          Controls HS driver impedance tuning for choke compensation
+          - <0> = no impedance offset
+          - <1> = reduce the impedance by 2 ohms
+          - <2> = reduce the impedance by 4 ohms
+          - <3> = reduce the impedance by 6 ohms
+        $ref: /schemas/types.yaml#/definitions/uint32
+        minimum: 0
+        maximum: 3
+        default: 0
+
+      st,tune-squelch-level:
+        description: |
+          Tunes the squelch DC threshold value
+          - <0> = no shift in threshold
+          - <1> = threshold shift by +7 mV
+          - <2> = threshold shift by -5 mV
+          - <3> = threshold shift by +14 mV
+        $ref: /schemas/types.yaml#/definitions/uint32
+        minimum: 0
+        maximum: 3
+        default: 0
+
+      st,enable-hs-rx-gain-eq:
+        description: Enables the HS Rx gain equalizer
+        type: boolean
+
+      st,tune-hs-rx-offset:
+        description: |
+          Adjusts the HS Rx offset
+          - <0> = no offset
+          - <1> = offset of +5 mV
+          - <2> = offset of +10 mV
+          - <3> = offset of -5 mV
+        $ref: /schemas/types.yaml#/definitions/uint32
+        minimum: 0
+        maximum: 3
+        default: 0
+
+      st,no-hs-ftime-ctrl:
+        description: Disables the HS fall time control of single ended signals during pre-emphasis
+        type: boolean
+
+      st,no-lsfs-sc:
+        description: Disables the short circuit protection in LS/FS driver
+        type: boolean
+
+      st,enable-hs-tx-staggering:
+        description: Enables the basic staggering in HS Tx mode
+        type: boolean
+
     allOf:
       - if:
           properties:
@@ -137,6 +250,14 @@ examples:
             reg = <0>;
             phy-supply = <&vdd_usb>;
             #phy-cells = <0>;
+            st,tune-hs-dc-level = <2>;
+            st,enable-fs-rftime-tuning;
+            st,enable-hs-rftime-reduction;
+            st,trim-hs-current = <15>;
+            st,trim-hs-impedance = <1>;
+            st,tune-squelch-level = <3>;
+            st,tune-hs-rx-offset = <2>;
+            st,no-lsfs-sc;
             connector {
                 compatible = "usb-a-connector";
                 vbus-supply = <&vbus_sw>;
@@ -147,6 +268,14 @@ examples:
             reg = <1>;
             phy-supply = <&vdd_usb>;
             #phy-cells = <1>;
+            st,tune-hs-dc-level = <2>;
+            st,enable-fs-rftime-tuning;
+            st,enable-hs-rftime-reduction;
+            st,trim-hs-current = <15>;
+            st,trim-hs-impedance = <1>;
+            st,tune-squelch-level = <3>;
+            st,tune-hs-rx-offset = <2>;
+            st,no-lsfs-sc;
         };
     };
 ...