[RFC PATCH] usb: musb: try a race-free wakeup

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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@xxxxxxxxxxxxx>
---

If this  what we are going to do then I would fixup other glue layer as well.

 drivers/usb/musb/musb_core.c    | 5 +----
 drivers/usb/musb/musb_core.h    | 1 +
 drivers/usb/musb/musb_dsps.c    | 5 +++++
 drivers/usb/musb/musb_virthub.c | 1 +
 4 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/musb/musb_core.c b/drivers/usb/musb/musb_core.c
index b841ee0bff06..8343bbc3985d 100644
--- a/drivers/usb/musb/musb_core.c
+++ b/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->state = OTG_STATE_A_HOST;
 				musb->is_active = 1;
-				musb_host_resume_root_hub(musb);
 				break;
 			case OTG_STATE_B_WAIT_ACON:
 				musb->xceiv->state = OTG_STATE_B_PERIPHERAL;
diff --git a/drivers/usb/musb/musb_core.h b/drivers/usb/musb/musb_core.h
index 414e57a984bb..803a997e56d2 100644
--- a/drivers/usb/musb/musb_core.h
+++ b/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;
diff --git a/drivers/usb/musb/musb_dsps.c b/drivers/usb/musb/musb_dsps.c
index a16a6449b668..14db5435e1cd 100644
--- a/drivers/usb/musb/musb_dsps.c
+++ b/drivers/usb/musb/musb_dsps.c
@@ -898,6 +898,11 @@ static int dsps_resume(struct device *dev)
 	dsps_writel(mbase, wrp->tx_mode, glue->context.tx_mode);
 	dsps_writel(mbase, wrp->rx_mode, glue->context.rx_mode);
 	setup_timer(&glue->timer, otg_timer, (unsigned long) musb);
+	if (musb->need_finish_resume) {
+		musb->need_finish_resume = 0;
+		schedule_delayed_work(&musb->finish_resume_work,
+				      msecs_to_jiffies(20));
+	}
 
 	return 0;
 }
diff --git a/drivers/usb/musb/musb_virthub.c b/drivers/usb/musb/musb_virthub.c
index e2d2d8c9891b..66d2996e9ed0 100644
--- a/drivers/usb/musb/musb_virthub.c
+++ b/drivers/usb/musb/musb_virthub.c
@@ -72,6 +72,7 @@ void musb_host_finish_resume(struct work_struct *work)
 	musb->xceiv->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)
-- 
2.1.1

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