usb: musb: try a race-free wakeup

Attaching a keyboard, using it as a wakeup via
|for f in $(find /sys/devices/ocp.3/47400000.usb -name wakeup)
|do
|	echo enabled > $f
|done

going into standby
|  echo standby >  /sys/power/state

and now a wake up by a pressing a key.
What happens is that the system wakes up but the USB device is dead. The
USB stack tries to send a few control URBs but nothing comes back.
Eventually it gaves up and the device remains dead:
|[  632.559678] PM: Wakeup source USB1_PHY
|[  632.581074] PM: noirq resume of devices complete after 21.261 msecs
|[  632.607521] PM: early resume of devices complete after 10.360 msecs
|[  632.616854] net eth2: initializing cpsw version 1.12 (0)
|[  632.704126] net eth2: phy found : id is : 0x4dd074
|[  636.704048] libphy: 4a101000.mdio:00 - Link is Up - 1000/Full
|[  638.444620] usb 1-1: reset low-speed USB device number 2 using musb-hdrc
|[  653.713435] usb 1-1: device descriptor read/64, error -110
|[  669.093435] usb 1-1: device descriptor read/64, error -110
|[  669.473424] usb 1-1: reset low-speed USB device number 2 using musb-hdrc
|[  684.743436] usb 1-1: device descriptor read/64, error -110
|[  690.065097] PM: resume of devices complete after 57450.744 msecs
|[  690.076601] PM: Finishing wakeup.
|[  690.076627] Restarting tasks ...

It seems that since we got woken up via MUSB_INTR_RESUME the
musb_host_finish_resume() callback is executed before the
resume-callbacks of the PHY and glue layer are invoked. If I delay it
until the glue layer resumed then I don't see this problem.

I also move musb_host_resume_root_hub() into that callback since I don't
see any reason in doing anything resume-link if there are still pieces
not restored.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/musb/musb_core.c

@@ -478,13 +478,10 @@ static irqreturn_t musb_stage0_irq(struct musb *musb, u8 int_usb,
 						| MUSB_PORT_STAT_RESUME;
 				musb->rh_timer = jiffies
 						 + msecs_to_jiffies(20);
-				schedule_delayed_work(
-					&musb->finish_resume_work,
-					msecs_to_jiffies(20));
+				musb->need_finish_resume = 1;
 
 				musb->xceiv->otg->state = OTG_STATE_A_HOST;
 				musb->is_active = 1;
-				musb_host_resume_root_hub(musb);
 				break;
 			case OTG_STATE_B_WAIT_ACON:
 				musb->xceiv->otg->state = OTG_STATE_B_PERIPHERAL;
@@ -2319,6 +2316,11 @@ static int musb_resume(struct device *dev)
 	mask = MUSB_DEVCTL_BDEVICE | MUSB_DEVCTL_FSDEV | MUSB_DEVCTL_LSDEV;
 	if ((devctl & mask) != (musb->context.devctl & mask))
 		musb->port1_status = 0;
+	if (musb->need_finish_resume) {
+		musb->need_finish_resume = 0;
+		schedule_delayed_work(&musb->finish_resume_work,
+				      msecs_to_jiffies(20));
+	}
 	return 0;
 }
 

drivers/usb/musb/musb_core.h

@@ -390,6 +390,7 @@ struct musb {
 
 	/* is_suspended means USB B_PERIPHERAL suspend */
 	unsigned		is_suspended:1;
+	unsigned		need_finish_resume :1;
 
 	/* may_wakeup means remote wakeup is enabled */
 	unsigned		may_wakeup:1;

drivers/usb/musb/musb_virthub.c

@@ -72,6 +72,7 @@ void musb_host_finish_resume(struct work_struct *work)
 	musb->xceiv->otg->state = OTG_STATE_A_HOST;
 
 	spin_unlock_irqrestore(&musb->lock, flags);
+	musb_host_resume_root_hub(musb);
 }
 
 void musb_port_suspend(struct musb *musb, bool do_suspend)