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

[Sebastian Andrzej Siewior]

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-***@public.gmane.org>
---

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)