linux-kernel - [PATCH] usb: hub: try old enumeration scheme first for high speed devices

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Date:   Fri, 10 Aug 2018 23:01:42 +0800
From:   Zeng Tao <prime.zeng@...ilicon.com>
To:     <gregkh@...uxfoundation.org>, <stern@...land.harvard.edu>,
        <mathias.nyman@...ux.intel.com>, <drinkcat@...omium.org>,
        <felipe.balbi@...ux.intel.com>, <drake@...lessm.com>,
        <mike.looijmans@...ic.nl>, <joe@...ches.com>
CC:     Zeng Tao <prime.zeng@...ilicon.com>, <linux-usb@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH] usb: hub: try old enumeration scheme first for high speed devices

The new scheme is required just to support legacy low and full-speed
devices. For high speed devices, it will slower the enumeration speed.
So in this patch we try the "old" enumeration scheme first for high speed
devices.

Signed-off-by: Zeng Tao <prime.zeng@...ilicon.com>
---
 drivers/usb/core/hub.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 1fb2668..d265b19 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -2661,10 +2661,13 @@ static bool use_new_scheme(struct usb_device *udev, int retry,
 	int old_scheme_first_port =
 		port_dev->quirks & USB_PORT_QUIRK_OLD_SCHEME;
 
+	int quick_enumeration = (udev->speed == USB_SPEED_HIGH);
+
 	if (udev->speed >= USB_SPEED_SUPER)
 		return false;
 
-	return USE_NEW_SCHEME(retry, old_scheme_first_port || old_scheme_first);
+	return USE_NEW_SCHEME(retry, old_scheme_first_port || old_scheme_first
+			      || quick_enumeration);
 }
 
 /* Is a USB 3.0 port in the Inactive or Compliance Mode state?
-- 
2.7.4