[3.11.y.z extended stable] Patch "usb: musb: call musb_start() only once in OTG mode" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    usb: musb: call musb_start() only once in OTG mode

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 26d6aa2c327dfd4c8dd2d9a94affff2cb6f29ec1 Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy at linutronix.de>
Date: Tue, 15 Oct 2013 18:29:22 +0200
Subject: usb: musb: call musb_start() only once in OTG mode

commit ae44df2e21b50f9fff28ac75c57e399c04df812c upstream.

In commit 001dd84 ("usb: musb: start musb on the udc side, too") it was
ensured that the state engine is started also in OTG mode after a
removal / insertion of the gadget.
Unfortunately this change also introduced a bug: If the device is
configured as OTG and it connected with a remote host _without_ loading
a gadget then we bug() later (because musb->otg->gadget is not
initialized).
Initially I assumed it might be nice to have the host part of musb in
OTG mode working without having a gadget loaded. This bug and fact that
it wasn't working like this before the host/gadget split made me realize
that this was a silly idea.
This patch now introduces back the old behavior where in OTG mode the
host mode is only working after the gadget has been loaded.

Cc: Daniel Mack <zonque at gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy at linutronix.de>
Signed-off-by: Felipe Balbi <balbi at ti.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/usb/musb/musb_virthub.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/musb/musb_virthub.c b/drivers/usb/musb/musb_virthub.c
index d1d6b83..9af6bba 100644
--- a/drivers/usb/musb/musb_virthub.c
+++ b/drivers/usb/musb/musb_virthub.c
@@ -220,6 +220,23 @@ int musb_hub_status_data(struct usb_hcd *hcd, char *buf)
 	return retval;
 }

+static int musb_has_gadget(struct musb *musb)
+{
+	/*
+	 * In host-only mode we start a connection right away. In OTG mode
+	 * we have to wait until we loaded a gadget. We don't really need a
+	 * gadget if we operate as a host but we should not start a session
+	 * as a device without a gadget or else we explode.
+	 */
+#ifdef CONFIG_USB_MUSB_HOST
+	return 1;
+#else
+	if (musb->port_mode == MUSB_PORT_MODE_HOST)
+		return 1;
+	return musb->g.dev.driver != NULL;
+#endif
+}
+
 int musb_hub_control(
 	struct usb_hcd	*hcd,
 	u16		typeReq,
@@ -362,7 +379,7 @@ int musb_hub_control(
 			 * initialization logic, e.g. for OTG, or change any
 			 * logic relating to VBUS power-up.
 			 */
-			if (!hcd->self.is_b_host)
+			if (!hcd->self.is_b_host && musb_has_gadget(musb))
 				musb_start(musb);
 			break;
 		case USB_PORT_FEAT_RESET:
--
1.8.3.2