From: Ramneek Mehresh <ramneek.mehresh@freescale.com>
To: <linux-kernel@vger.kernel.org>
CC: <balbi@ti.com>, <stern@rowland.harvard.edu>, <gregkh@linuxfoundation.org>,
        <linux-usb@vger.kernel.org>,
        Ramneek Mehresh <ramneek.mehresh@freescale.com>
Subject: [PATCH 7/7][v4]usb:fsl:otg: Add host-gadget drv sync delay
Date: Thu, 27 Aug 2015 22:13:07 +0530
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Resolve synchronization issue between host
and gadget drivers upon role-reversal.

Signed-off-by: Ramneek Mehresh <ramneek.mehresh@freescale.com>
Reviewed-by: Li Yang-R58472 <LeoLi@freescale.com>
Reviewed-by: Fleming Andrew-AFLEMING <AFLEMING@freescale.com>
Tested-by: Fleming Andrew-AFLEMING <AFLEMING@freescale.com>
---
 drivers/usb/phy/phy-fsl-usb.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/phy/phy-fsl-usb.c b/drivers/usb/phy/phy-fsl-usb.c
index 689516d..5d678ea 100644
--- a/drivers/usb/phy/phy-fsl-usb.c
+++ b/drivers/usb/phy/phy-fsl-usb.c
@@ -544,8 +544,18 @@ int fsl_otg_start_gadget(struct otg_fsm *fsm, int on)
 	dev = otg->gadget->dev.parent;
 
 	if (on) {
-		if (dev->driver->resume)
+		/*
+		 * Delay gadget resume to synchronize between host and gadget
+		 * drivers. Upon role-reversal host drv is shutdown by kernel
+		 * worker thread. By the time host drv shuts down, controller
+		 * gets programmed for gadget role. Shutting host drv after
+		 * this results in controller getting reset, and it stops
+		 * responding to otg events
+		 */
+		if (dev->driver->resume) {
+			msleep(1000);
 			dev->driver->resume(dev);
+		}
 	} else {
 		if (dev->driver->suspend)
 			dev->driver->suspend(dev, otg_suspend_state);
-- 
1.8.3.1

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