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

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: stable@vger.kernel.org # v3.11
Cc: Daniel Mack <zonque@gmail.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>

1 files changed, 18 insertions, 1 deletions

diff --git a/drivers/usb/musb/musb_virthub.c b/drivers/usb/musb/musb_virthub.c
index a523950c2b32..d8bbdb366beb 100644
--- a/drivers/usb/musb/musb_virthub.c
+++ b/drivers/usb/musb/musb_virthub.c
@@ -266,6 +266,23 @@ 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,
@@ -408,7 +425,7 @@ 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: