linux-kernel - [PATCH] xhci: Do warm-reset when both CAS and XDEV

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Date:   Mon, 10 Aug 2020 22:07:53 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     mathias.nyman@...el.com
Cc:     Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org (open list:USB XHCI DRIVER),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH] xhci: Do warm-reset when both CAS and XDEV_RESUME are set

Sometimes re-plugging a USB device during system sleep renders the device
useless:
[  173.418345] xhci_hcd 0000:00:14.0: Get port status 2-4 read: 0x14203e2, return 0x10262
...
[  176.496485] usb 2-4: Waited 2000ms for CONNECT
[  176.496781] usb usb2-port4: status 0000.0262 after resume, -19
[  176.497103] usb 2-4: can't resume, status -19
[  176.497438] usb usb2-port4: logical disconnect

Because PLS equals to XDEV_RESUME, xHCI driver reports U3 to usbcore,
despite of CAS bit is flagged.

So proritize CAS over XDEV_RESUME to let usbcore handle warm-reset for
the port.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
---
 drivers/usb/host/xhci-hub.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/drivers/usb/host/xhci-hub.c b/drivers/usb/host/xhci-hub.c
index c3554e37e09f..4e14e164cb68 100644
--- a/drivers/usb/host/xhci-hub.c
+++ b/drivers/usb/host/xhci-hub.c
@@ -740,15 +740,6 @@ static void xhci_hub_report_usb3_link_state(struct xhci_hcd *xhci,
 {
 	u32 pls = status_reg & PORT_PLS_MASK;
 
-	/* resume state is a xHCI internal state.
-	 * 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) {
-		*status |= USB_SS_PORT_LS_U3;
-		return;
-	}
-
 	/* When the CAS bit is set then warm reset
 	 * should be performed on port
 	 */
@@ -770,6 +761,16 @@ static void xhci_hub_report_usb3_link_state(struct xhci_hcd *xhci,
 		 */
 		pls |= USB_PORT_STAT_CONNECTION;
 	} else {
+		/*
+		 * Resume state is an xHCI internal state.  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) {
+			*status |= USB_SS_PORT_LS_U3;
+			return;
+		}
+
 		/*
 		 * If CAS bit isn't set but the Port is already at
 		 * Compliance Mode, fake a connection so the USB core
-- 
2.17.1