Re: Discussion about implementation of usb port power off mechanism for port with device

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On 2012年07月23日 23:27, Alan Stern wrote:
On Mon, 23 Jul 2012, Lan Tianyu wrote:

@@ -3027,6 +3070,24 @@ int usb_port_resume(struct usb_device *u
    	int		status;
    	u16		portchange, portstatus;

+	if (hub->ports[port1 - 1]->port_power_policy == USB_PORT_POWER_AUTO
+			&&  hub->ports[port1 - 1]->power_state == USB_PORT_POWER_STATE_OFF) {
+		set_port_feature(udev->parent, port1, USB_PORT_FEAT_POWER);
+		/*
+		 * Wait for usb hub port to be reconnected in order to make
+		 * the resume procedure successful.
+		 */
+		status = usb_port_wait_for_connected(hub, port1);
+		if (status<  0) {
+			dev_dbg(&udev->dev, "can't get reconnection after setting  port " \
+				"power on, status %d\n", status);
+			return status;
+		}
+		hub->ports[port1 - 1]->power_state = USB_PORT_POWER_STATE_ON;
+		pr_info("%s: port%d connect state on %ld\n", __func__, port1, jiffies);
+	}
    	/* Skip the initial Clear-Suspend step for a remote wakeup */
    	status = hub_port_status(hub, port1,&portstatus,&portchange);
    	if (status == 0&&  !port_is_suspended(hub, portstatus))

A few lines later the driver does:

	set_bit(port1, hub->busy_bits);

You merely need to move this line up before the point where you turn
port power back on.  Make it the first executable line of the function.

I test and it works. Thanks

Alan Stern

Best Regards
Tianyu Lan
linux kernel enabling team
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