linux-kernel - [PATCH v4 1/2] dt-bindings: usb: add "hub,interval" property

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Date:   Tue,  3 Dec 2019 18:15:36 +0800
From:   Ikjoon Jang <ikjn@...omium.org>
To:     devicetree@...r.kernel.org
Cc:     GregKroah-Hartman <gregkh@...uxfoundation.org>,
        RobHerring <robh+dt@...nel.org>,
        MarkRutland <mark.rutland@....com>,
        AlanStern <stern@...land.harvard.edu>,
        SuwanKim <suwan.kim027@...il.com>,
        "GustavoA . R . Silva" <gustavo@...eddedor.com>,
        IkjoonJang <ikjn@...omium.org>, JohanHovold <johan@...nel.org>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        drinkcat@...omium.org
Subject: [PATCH v4 1/2] dt-bindings: usb: add "hub,interval" property

Add "hub,interval" property to usb-device, so hub device can override
endpoint descriptor's bInterval.

When we know reducing autosuspend delay for built-in HIDs is better for
power saving, we can reduce it to the optimal value. But if a parent hub
has a long bInterval, mouse lags a lot from more frequent autosuspend.
So this enables overriding bInterval for a hard wired hub device only
when we know that reduces the power consumption.

Signed-off-by: Ikjoon Jang <ikjn@...omium.org>
---
 Documentation/devicetree/bindings/usb/usb-device.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/devicetree/bindings/usb/usb-device.txt b/Documentation/devicetree/bindings/usb/usb-device.txt
index 036be172b1ae..44bef2ff2704 100644
--- a/Documentation/devicetree/bindings/usb/usb-device.txt
+++ b/Documentation/devicetree/bindings/usb/usb-device.txt
@@ -66,6 +66,9 @@ Required properties for host-controller nodes with device nodes:
 - #size-cells: shall be 0
 
 
+Optional properties for hub nodes
+- hub,interval: bInterval of status change endpoint. The range is 1-255.
+
 Example:
 
 &usb1 {	/* host controller */
@@ -75,6 +78,7 @@ Example:
 	hub@1 {		/* hub connected to port 1 */
 		compatible = "usb5e3,608";
 		reg = <1>;
+		hub,interval = <8>;
 	};
 
 	device@2 {	/* device connected to port 2 */
-- 
2.24.0.393.g34dc348eaf-goog