Patch "usb: dwc3: gadget: Prevent losing events in event cache" has been added to the 4.9-stable tree

Patch "usb: dwc3: gadget: Prevent losing events in event cache" has been added to the 4.9-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    usb: dwc3: gadget: Prevent losing events in event cache

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     usb-dwc3-gadget-prevent-losing-events-in-event-cache.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From d325a1de49d61ee11aca58a529571c91ecea7879 Mon Sep 17 00:00:00 2001
From: Thinh Nguyen <Thinh.Nguyen@synopsys.com>
Date: Thu, 11 May 2017 17:26:47 -0700
Subject: usb: dwc3: gadget: Prevent losing events in event cache

From: Thinh Nguyen <Thinh.Nguyen@synopsys.com>

commit d325a1de49d61ee11aca58a529571c91ecea7879 upstream.

The dwc3 driver can overwite its previous events if its top-half IRQ
handler (TH) gets invoked again before processing the events in the
cache. We see this as a hang in the file transfer and the host will
attempt to reset the device. TH gets the event count and deasserts the
interrupt line by writing DWC3_GEVNTSIZ_INTMASK to DWC3_GEVNTSIZ. If
there's a new event coming between reading the event count and interrupt
deassertion, dwc3 will lose previous pending events. More generally, we
will see 0 event count, which should not affect anything.

This shouldn't be possible in the current dwc3 implementation. However,
through testing and reading the PCIe trace, the TH occasionally still
gets invoked one more time after HW interrupt deassertion. (With PCIe
legacy interrupts, TH is called repeatedly as long as the interrupt line
is asserted). We suspect that there is a small detection delay in the
SW.

To avoid this issue, Check DWC3_EVENT_PENDING flag to determine if the
events are processed in the bottom-half IRQ handler. If not, return
IRQ_HANDLED and don't process new event.

Signed-off-by: Thinh Nguyen <thinhn@synopsys.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/usb/dwc3/gadget.c |    9 +++++++++
 1 file changed, 9 insertions(+)

--- a/drivers/usb/dwc3/gadget.c
+++ b/drivers/usb/dwc3/gadget.c
@@ -2856,6 +2856,15 @@ static irqreturn_t dwc3_check_event_buf(
 		return IRQ_HANDLED;
 	}
 
+	/*
+	 * With PCIe legacy interrupt, test shows that top-half irq handler can
+	 * be called again after HW interrupt deassertion. Check if bottom-half
+	 * irq event handler completes before caching new event to prevent
+	 * losing events.
+	 */
+	if (evt->flags & DWC3_EVENT_PENDING)
+		return IRQ_HANDLED;
+
 	count = dwc3_readl(dwc->regs, DWC3_GEVNTCOUNT(0));
 	count &= DWC3_GEVNTCOUNT_MASK;
 	if (!count)


Patches currently in stable-queue which might be from Thinh.Nguyen@synopsys.com are

queue-4.9/usb-dwc3-gadget-prevent-losing-events-in-event-cache.patch