linux-kernel - [PATCH 3.2 098/110] xhci: report U3 when link is in resume state

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Message-ID: <lsq.1439201551.927047293@decadent.org.uk>
Date:	Mon, 10 Aug 2015 12:12:31 +0200
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Zhuang Jin Can" <jin.can.zhuang@...el.com>,
	"Mathias Nyman" <mathias.nyman@...ux.intel.com>,
	"Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Subject: [PATCH 3.2 098/110] xhci: report U3 when link is in resume state

3.2.71-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Zhuang Jin Can <jin.can.zhuang@...el.com>

commit 243292a2ad3dc365849b820a64868927168894ac upstream.

xhci_hub_report_usb3_link_state() returns pls as U0 when the link
is in resume state, and this causes usb core to think the link is in
U0 while actually it's in resume state. When usb core transfers
control request on the link, it fails with TRB error as the link
is not ready for transfer.

To fix the issue, report U3 when the link is in resume state, thus
usb core knows the link it's not ready for transfer.

Signed-off-by: Zhuang Jin Can <jin.can.zhuang@...el.com>
Signed-off-by: Mathias Nyman <mathias.nyman@...ux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/usb/host/xhci-hub.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/drivers/usb/host/xhci-hub.c
+++ b/drivers/usb/host/xhci-hub.c
@@ -449,10 +449,13 @@ static void xhci_hub_report_link_state(s
 	u32 pls = status_reg & PORT_PLS_MASK;
 
 	/* resume state is a xHCI internal state.
-	 * Do not report it to usb core.
+	 * Do not report it to usb core, instead, pretend to be U3,
+	 * thus usb core knows it's not ready for transfer
 	 */
-	if (pls == XDEV_RESUME)
+	if (pls == XDEV_RESUME) {
+		*status |= USB_SS_PORT_LS_U3;
 		return;
+	}
 
 	/* When the CAS bit is set then warm reset
 	 * should be performed on port

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