usb: musb: fix remote wakeup racing with suspend

It has been observed that writing 0xF2 to the power register while it
reads as 0xF4 results in the register having the value 0xF0, i.e. clearing
RESUME and setting SUSPENDM in one go does not work. It might also violate
the USB spec to transition directly from resume to suspend, especially
when not taking T_DRSMDN into account. But this is what happens when a
remote wakeup occurs between SetPortFeature USB_PORT_FEAT_SUSPEND on the
root hub and musb_bus_suspend being called.

This commit returns -EBUSY when musb_bus_suspend is called while remote
wakeup is signalled and thus avoids to reset the RESUME bit. Ignoring
this error when musb_port_suspend is called from musb_hub_control is ok.

Signed-off-by: Daniel Glöckner <dg@emlix.com>
Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 15 insertions, 10 deletions

diff --git a/drivers/usb/musb/musb_virthub.c b/drivers/usb/musb/musb_virthub.c
index 5165d2b07ade..2f8dd9826e94 100644
--- a/drivers/usb/musb/musb_virthub.c
+++ b/drivers/usb/musb/musb_virthub.c
@@ -48,14 +48,14 @@ void musb_host_finish_resume(struct work_struct *work)
 	spin_unlock_irqrestore(&musb->lock, flags);
 }
 
-void musb_port_suspend(struct musb *musb, bool do_suspend)
+int musb_port_suspend(struct musb *musb, bool do_suspend)
 {
 	struct usb_otg	*otg = musb->xceiv->otg;
 	u8		power;
 	void __iomem	*mbase = musb->mregs;
 
 	if (!is_host_active(musb))
-		return;
+		return 0;
 
 	/* NOTE:  this doesn't necessarily put PHY into low power mode,
 	 * turning off its clock; that's a function of PHY integration and
@@ -66,16 +66,20 @@ void musb_port_suspend(struct musb *musb, bool do_suspend)
 	if (do_suspend) {
 		int retries = 10000;
 
-		power &= ~MUSB_POWER_RESUME;
-		power |= MUSB_POWER_SUSPENDM;
-		musb_writeb(mbase, MUSB_POWER, power);
+		if (power & MUSB_POWER_RESUME)
+			return -EBUSY;
 
-		/* Needed for OPT A tests */
-		power = musb_readb(mbase, MUSB_POWER);
-		while (power & MUSB_POWER_SUSPENDM) {
+		if (!(power & MUSB_POWER_SUSPENDM)) {
+			power |= MUSB_POWER_SUSPENDM;
+			musb_writeb(mbase, MUSB_POWER, power);
+
+			/* Needed for OPT A tests */
 			power = musb_readb(mbase, MUSB_POWER);
-			if (retries-- < 1)
-				break;
+			while (power & MUSB_POWER_SUSPENDM) {
+				power = musb_readb(mbase, MUSB_POWER);
+				if (retries-- < 1)
+					break;
+			}
 		}
 
 		musb_dbg(musb, "Root port suspended, power %02x", power);
@@ -111,6 +115,7 @@ void musb_port_suspend(struct musb *musb, bool do_suspend)
 		schedule_delayed_work(&musb->finish_resume_work,
 				      msecs_to_jiffies(USB_RESUME_TIMEOUT));
 	}
+	return 0;
 }
 
 void musb_port_reset(struct musb *musb, bool do_reset)