linux-kernel - [RFC][PATCH 2/5 v2] usb: dwc2: Workaround case where GOTGCTL state is wrong

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Message-Id: <1481952713-29829-3-git-send-email-john.stultz@linaro.org>
Date:   Fri, 16 Dec 2016 21:31:50 -0800
From:   John Stultz <john.stultz@...aro.org>
To:     lkml <linux-kernel@...r.kernel.org>
Cc:     John Stultz <john.stultz@...aro.org>,
        Wei Xu <xuwei5@...ilicon.com>,
        Guodong Xu <guodong.xu@...aro.org>,
        Amit Pundir <amit.pundir@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        John Youn <johnyoun@...opsys.com>,
        Douglas Anderson <dianders@...omium.org>,
        Chen Yu <chenyu56@...wei.com>,
        Vardan Mikayelyan <mvardan@...opsys.com>,
        Kishon Vijay Abraham I <kishon@...com>,
        Felipe Balbi <felipe.balbi@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-usb@...r.kernel.org
Subject: [RFC][PATCH 2/5 v2] usb: dwc2: Workaround case where GOTGCTL state is wrong

When removing a USB-A to USB-otg adapter cable, we get a change
status irq, and then in dwc2_conn_id_status_change, we
erroniously see the GOTGCTL_CONID_B flag set. This causes us to
get  stuck in the "while (!dwc2_is_device_mode(hsotg))" loop,
spitting out "Waiting for Peripheral Mode, Mode=Host" warnings
until it fails out many seconds later.

This patch works around the issue by re-reading the GOTGCTL
state to check if the GOTGCTL_CONID_B is still set and if not
restarting the change status logic.

I suspect this isn't the best solution, but it seems to work
well for me.

Feedback would be greatly appreciated!

Cc: Wei Xu <xuwei5@...ilicon.com>
Cc: Guodong Xu <guodong.xu@...aro.org>
Cc: Amit Pundir <amit.pundir@...aro.org>
Cc: Rob Herring <robh+dt@...nel.org>
Cc: John Youn <johnyoun@...opsys.com>
Cc: Douglas Anderson <dianders@...omium.org>
Cc: Chen Yu <chenyu56@...wei.com>
Cc: Vardan Mikayelyan <mvardan@...opsys.com>
Cc: Kishon Vijay Abraham I <kishon@...com>
Cc: Felipe Balbi <felipe.balbi@...ux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: linux-usb@...r.kernel.org
Acked-by: John Youn <johnyoun@...opsys.com>
Reviewed-by: Vardan Mikayelyan <mvardan@...opsys.com>
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
v2: Rework goto logic suggested by Vardan, and add a comment
---
 drivers/usb/dwc2/hcd.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
index 911c3b3..b60307a 100644
--- a/drivers/usb/dwc2/hcd.c
+++ b/drivers/usb/dwc2/hcd.c
@@ -3241,6 +3241,14 @@ static void dwc2_conn_id_status_change(struct work_struct *work)
 				 dwc2_is_host_mode(hsotg) ? "Host" :
 				 "Peripheral");
 			usleep_range(20000, 40000);
+			/*
+			 * Sometimes the initial GOTGCTRL read is wrong, so
+			 * check it again and jump to host mode if that was
+			 * the case.
+			 */
+			gotgctl = dwc2_readl(hsotg->regs + GOTGCTL);
+			if (!(gotgctl & GOTGCTL_CONID_B))
+				goto host;
 			if (++count > 250)
 				break;
 		}
@@ -3255,6 +3263,7 @@ static void dwc2_conn_id_status_change(struct work_struct *work)
 		spin_unlock_irqrestore(&hsotg->lock, flags);
 		dwc2_hsotg_core_connect(hsotg);
 	} else {
+host:
 		/* A-Device connector (Host Mode) */
 		dev_dbg(hsotg->dev, "connId A\n");
 		while (!dwc2_is_host_mode(hsotg)) {
-- 
2.7.4