[PATCH v3 2/7] dt-bindings: phy: mediatek,tphy: add property to set pre-emphasis

[Chunfeng Yun]

Add a property to set usb2 phy's pre-emphasis, which used to widen eye
opening and boost eye swing.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
Signed-off-by: Chunfeng Yun <chunfeng.yun@xxxxxxxxxxxx>
---
v3: add acked-by Krzysztof
v2: Add more description suggested by Krzysztof
---
 .../devicetree/bindings/phy/mediatek,tphy.yaml         | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Documentation/devicetree/bindings/phy/mediatek,tphy.yaml b/Documentation/devicetree/bindings/phy/mediatek,tphy.yaml
index 848edfb1f677..e0754fb44451 100644
--- a/Documentation/devicetree/bindings/phy/mediatek,tphy.yaml
+++ b/Documentation/devicetree/bindings/phy/mediatek,tphy.yaml
@@ -219,6 +219,16 @@ patternProperties:
         minimum: 1
         maximum: 15
 
+      mediatek,pre-emphasis:
+        description:
+          The level of pre-emphasis which used to widen the eye opening and
+          boost eye swing, the unit step is about 4.16% increment; e.g. the
+          level 1 means amplitude increases about 4.16%, the level 2 is about
+          8.3% etc. (U2 phy)
+        $ref: /schemas/types.yaml#/definitions/uint32
+        minimum: 1
+        maximum: 3
+
       mediatek,bc12:
         description:
           Specify the flag to enable BC1.2 if support it
-- 
2.18.0