linux-kernel - [RFC][PATCH 4/5 v2] usb: dwc2: Avoid suspending if we're in gadget mode

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Date:   Fri, 16 Dec 2016 21:31:52 -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 4/5 v2] usb: dwc2: Avoid suspending if we're in gadget mode

I've found when booting HiKey with the usb gadget cable attached
if I then try to connect via adb, I get an infinite spew of:

dwc2 f72c0000.usb: dwc2_hsotg_ep_sethalt(ep ffffffc0790ecb18 ep1out, 0)
dwc2 f72c0000.usb: dwc2_hsotg_ep_sethalt(ep ffffffc0790eca18 ep1in, 0)

It seems that the usb autosuspend is suspending the bus shortly
after bootup when the gadget cable is attached. So when adbd
then tries to use the device, it doesn't work and it then tries
to restart it over and over via the ep_sethalt calls (via
FUNCTIONFS_CLEAR_HALT ioctl).

Chen Yu suggested this patch to avoid suspending if we're
in device mode, and it avoids the problem.

This doesn't remove the need for the previous patch, to resume
the port when we switch to gadget mode from host mode. But it
does seem to resolve the issue.

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
Suggested-by: Chen Yu <chenyu56@...wei.com>
Signed-off-by: John Stultz <john.stultz@...aro.org>
---
 drivers/usb/dwc2/hcd.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/usb/dwc2/hcd.c b/drivers/usb/dwc2/hcd.c
index a089946..6e4ec8a 100644
--- a/drivers/usb/dwc2/hcd.c
+++ b/drivers/usb/dwc2/hcd.c
@@ -4383,6 +4383,9 @@ static int _dwc2_hcd_suspend(struct usb_hcd *hcd)
 	if (!HCD_HW_ACCESSIBLE(hcd))
 		goto unlock;
 
+	if (hsotg->op_state == OTG_STATE_B_PERIPHERAL)
+		goto unlock;
+
 	if (!hsotg->params.hibernation)
 		goto skip_power_saving;
 
-- 
2.7.4