[PATCH v3 1/3] dt-bindings: usb: mtk-xhci: add a property for Gen1 isoc-in transfer issue

[Chunfeng Yun]

For Gen1 isoc-in endpoint on controller before about SSUSB IPM v1.6.0, it
still send out unexpected ACK after receiving a short packet in burst
transfer, this will cause an exception on connected device, specially for
a 4k camera.
Add a quirk property "rx-fifo-depth" to work around this hardware issue,
prefer to use 3k bytes;
The side-effect is that may cause performance drop about 10%, including
bulk transfer.

Signed-off-by: Chunfeng Yun <chunfeng.yun at mediatek.com>
---
v3: add fifo depth unit, change the value range from 0-3 to 1-4
v2: change 'mediatek,rxfifo-depth' to 'rx-fifo-depth'
---
 .../devicetree/bindings/usb/mediatek,mtk-xhci.yaml   | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.yaml b/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.yaml
index e9644e333d78..9478b7031796 100644
--- a/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.yaml
+++ b/Documentation/devicetree/bindings/usb/mediatek,mtk-xhci.yaml
@@ -124,6 +124,18 @@ properties:
       defined in the xHCI spec on MTK's controller.
     default: 5000
 
+  rx-fifo-depth:
+    $ref: /schemas/types.yaml#/definitions/uint32
+    description:
+      It is a quirk used to work around Gen1 isoc-in endpoint transfer issue
+      that still send out unexpected ACK after device finish the burst transfer
+      with a short packet and cause an exception, specially on a 4K camera
+      device, it happens on controller before about IPM v1.6.0; the side-effect
+      is that may cause performance drop about 10%, include bulk transfer,
+      prefer to use 3 here. The unit is 1K bytes.
+    minimum: 1
+    maximum: 4
+
   # the following properties are only used for case 1
   wakeup-source:
     description: enable USB remote wakeup, see power/wakeup-source.txt
-- 
2.18.0