linux-kernel - [PATCH 3.18 49/54] xhci: Prevent U1/U2 link pm states if exit latency is too long

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Date:   Tue, 11 Dec 2018 16:41:37 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Mathias Nyman <mathias.nyman@...ux.intel.com>
Subject: [PATCH 3.18 49/54] xhci: Prevent U1/U2 link pm states if exit latency is too long

3.18-stable review patch.  If anyone has any objections, please let me know.

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

From: Mathias Nyman <mathias.nyman@...ux.intel.com>

commit 0472bf06c6fd33c1a18aaead4c8f91e5a03d8d7b upstream.

Don't allow USB3 U1 or U2 if the latency to wake up from the U-state
reaches the service interval for a periodic endpoint.

This is according to xhci 1.1 specification section 4.23.5.2 extra note:

"Software shall ensure that a device is prevented from entering a U-state
 where its worst case exit latency approaches the ESIT."

Allowing too long exit latencies for periodic endpoint confuses xHC
internal scheduling, and new devices may fail to enumerate with a
"Not enough bandwidth for new device state" error from the host.

Cc: <stable@...r.kernel.org>
Signed-off-by: Mathias Nyman <mathias.nyman@...ux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/usb/host/xhci.c |   16 ++++++++++++++++
 1 file changed, 16 insertions(+)

--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -4377,6 +4377,14 @@ static u16 xhci_calculate_u1_timeout(str
 {
 	unsigned long long timeout_ns;
 
+	/* Prevent U1 if service interval is shorter than U1 exit latency */
+	if (usb_endpoint_xfer_int(desc) || usb_endpoint_xfer_isoc(desc)) {
+		if (xhci_service_interval_to_ns(desc) <= udev->u1_params.mel) {
+			dev_dbg(&udev->dev, "Disable U1, ESIT shorter than exit latency\n");
+			return USB3_LPM_DISABLED;
+		}
+	}
+
 	if (xhci->quirks & XHCI_INTEL_HOST)
 		timeout_ns = xhci_calculate_intel_u1_timeout(udev, desc);
 	else
@@ -4433,6 +4441,14 @@ static u16 xhci_calculate_u2_timeout(str
 {
 	unsigned long long timeout_ns;
 
+	/* Prevent U2 if service interval is shorter than U2 exit latency */
+	if (usb_endpoint_xfer_int(desc) || usb_endpoint_xfer_isoc(desc)) {
+		if (xhci_service_interval_to_ns(desc) <= udev->u2_params.mel) {
+			dev_dbg(&udev->dev, "Disable U2, ESIT shorter than exit latency\n");
+			return USB3_LPM_DISABLED;
+		}
+	}
+
 	if (xhci->quirks & XHCI_INTEL_HOST)
 		timeout_ns = xhci_calculate_intel_u2_timeout(udev, desc);
 	else