usb: musb: start musb on the udc side, too

I have am335x-evm with one port running in OTG mode. Since commit
fe4cb091 ("usb: musb: gadget: remove hcd initialization") the loaded
gadget does non pop up on the host. All I see is
|usb 4-5: new high-speed USB device number 52 using ehci-pci
|usb 4-5: device descriptor read/64, error -110

Since a later commit 2cc65fea ("usb: musb: add musb_host_setup() and
musb_host_cleanup()) the gadget shows up on the host again but only
in OTG mode (because we have the host init code running). It does not
work in device only mode.
If running in OTG mode and the gadget is removed and added back (rmmod
followed by modprobe of a gadget) then the same error is pops up on the
host side.

This patch ensures that the gadget side also executes musb_start() which
puts the chip in "connect accept" mode. With this change the device
works in OTG & device mode and the gadget can be added & removed
multiple times.
A device (if musb is in OTG mode acting as a host) is only recognized if
it is attached during module load (musb_hdrc module). After the device
unplugged and plugged again the host does not recognize it. We get a
buch of errors if musb running in OTG mode, attached to a host and no
gadget is loaded. Bah.
This is one step forward. Host & device only mode should work. I will
look at OTG later. I looked at this before commit fe4cb091 and OTG wasn't
working there perfectly so I am not sure that it is a regression :)

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

drivers/usb/musb/musb_core.c

@@ -921,6 +921,52 @@ static void musb_generic_disable(struct musb *musb)
 
 }
 
+/*
+ * Program the HDRC to start (enable interrupts, dma, etc.).
+ */
+void musb_start(struct musb *musb)
+{
+	void __iomem    *regs = musb->mregs;
+	u8              devctl = musb_readb(regs, MUSB_DEVCTL);
+
+	dev_dbg(musb->controller, "<== devctl %02x\n", devctl);
+
+	/*  Set INT enable registers, enable interrupts */
+	musb->intrtxe = musb->epmask;
+	musb_writew(regs, MUSB_INTRTXE, musb->intrtxe);
+	musb->intrrxe = musb->epmask & 0xfffe;
+	musb_writew(regs, MUSB_INTRRXE, musb->intrrxe);
+	musb_writeb(regs, MUSB_INTRUSBE, 0xf7);
+
+	musb_writeb(regs, MUSB_TESTMODE, 0);
+
+	/* put into basic highspeed mode and start session */
+	musb_writeb(regs, MUSB_POWER, MUSB_POWER_ISOUPDATE
+			| MUSB_POWER_HSENAB
+			/* ENSUSPEND wedges tusb */
+			/* | MUSB_POWER_ENSUSPEND */
+		   );
+
+	musb->is_active = 0;
+	devctl = musb_readb(regs, MUSB_DEVCTL);
+	devctl &= ~MUSB_DEVCTL_SESSION;
+
+	/* session started after:
+	 * (a) ID-grounded irq, host mode;
+	 * (b) vbus present/connect IRQ, peripheral mode;
+	 * (c) peripheral initiates, using SRP
+	 */
+	if (musb->port_mode != MUSB_PORT_MODE_HOST &&
+			(devctl & MUSB_DEVCTL_VBUS) == MUSB_DEVCTL_VBUS) {
+		musb->is_active = 1;
+	} else {
+		devctl |= MUSB_DEVCTL_SESSION;
+	}
+
+	musb_platform_enable(musb);
+	musb_writeb(regs, MUSB_DEVCTL, devctl);
+}
+
 /*
  * Make the HDRC stop (disable interrupts, etc.);
  * reversible by musb_start

drivers/usb/musb/musb_core.h

@@ -503,6 +503,7 @@ static inline void musb_configure_ep0(struct musb *musb)
 extern const char musb_driver_name[];
 
 extern void musb_stop(struct musb *musb);
+extern void musb_start(struct musb *musb);
 
 extern void musb_write_fifo(struct musb_hw_ep *ep, u16 len, const u8 *src);
 extern void musb_read_fifo(struct musb_hw_ep *ep, u16 len, u8 *dst);

drivers/usb/musb/musb_gadget.c

@@ -1858,6 +1858,8 @@ static int musb_gadget_start(struct usb_gadget *g,
 	musb->xceiv->state = OTG_STATE_B_IDLE;
 	spin_unlock_irqrestore(&musb->lock, flags);
 
+	musb_start(musb);
+
 	/* REVISIT:  funcall to other code, which also
 	 * handles power budgeting ... this way also
 	 * ensures HdrcStart is indirectly called.

drivers/usb/musb/musb_virthub.c

@@ -44,52 +44,6 @@
 
 #include "musb_core.h"
 
-/*
-* Program the HDRC to start (enable interrupts, dma, etc.).
-*/
-static void musb_start(struct musb *musb)
-{
-	void __iomem	*regs = musb->mregs;
-	u8		devctl = musb_readb(regs, MUSB_DEVCTL);
-
-	dev_dbg(musb->controller, "<== devctl %02x\n", devctl);
-
-	/*  Set INT enable registers, enable interrupts */
-	musb->intrtxe = musb->epmask;
-	musb_writew(regs, MUSB_INTRTXE, musb->intrtxe);
-	musb->intrrxe = musb->epmask & 0xfffe;
-	musb_writew(regs, MUSB_INTRRXE, musb->intrrxe);
-	musb_writeb(regs, MUSB_INTRUSBE, 0xf7);
-
-	musb_writeb(regs, MUSB_TESTMODE, 0);
-
-	/* put into basic highspeed mode and start session */
-	musb_writeb(regs, MUSB_POWER, MUSB_POWER_ISOUPDATE
-						| MUSB_POWER_HSENAB
-						/* ENSUSPEND wedges tusb */
-						/* | MUSB_POWER_ENSUSPEND */
-						);
-
-	musb->is_active = 0;
-	devctl = musb_readb(regs, MUSB_DEVCTL);
-	devctl &= ~MUSB_DEVCTL_SESSION;
-
-	/* session started after:
-	 * (a) ID-grounded irq, host mode;
-	 * (b) vbus present/connect IRQ, peripheral mode;
-	 * (c) peripheral initiates, using SRP
-	 */
-	if (musb->port_mode != MUSB_PORT_MODE_HOST &&
-	    (devctl & MUSB_DEVCTL_VBUS) == MUSB_DEVCTL_VBUS) {
-		musb->is_active = 1;
-	} else {
-		devctl |= MUSB_DEVCTL_SESSION;
-	}
-
-	musb_platform_enable(musb);
-	musb_writeb(regs, MUSB_DEVCTL, devctl);
-}
-
 static void musb_port_suspend(struct musb *musb, bool do_suspend)
 {
 	struct usb_otg	*otg = musb->xceiv->otg;