patch "USB: musb: fix late external abort on suspend" added to usb-linus

This is a note to let you know that I've just added the patch titled

USB: musb: fix late external abort on suspend

to my usb git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From: Johan Hovold <[email protected]>
Date: Mon, 9 Oct 2017 22:46:08 -0500
Subject: USB: musb: fix late external abort on suspend

The musb delayed irq work was never flushed on suspend, something which since 4.9 can lead to an external abort if the work is scheduled after the grandparent's clock has been disabled:

PM: Suspending system (mem)
PM: suspend of devices complete after 125.224 msecs
PM: suspend devices took 0.132 seconds
PM: late suspend of devices complete after 7.423 msecs
PM: noirq suspend of devices complete after 7.083 msecs
suspend debug: Waiting for 5 second(s).
Unhandled fault: external abort on non-linefetch (0x1008) at 0xd0262c60
...
[<c054880c>] (musb_default_readb) from [<c0547b5c>] (musb_irq_work+0x48/0x220) [<c0547b5c>] (musb_irq_work) from [<c014f8a4>] (process_one_work+0x1f4/0x758) [<c014f8a4>] (process_one_work) from [<c014fe5c>] (worker_thread+0x54/0x514) [<c014fe5c>] (worker_thread) from [<c015704c>] (kthread+0x128/0x158) [<c015704c>] (kthread) from [<c0109330>] (ret_from_fork+0x14/0x24)

Commit 2bff3916fda9 ("usb: musb: Fix PM for hub disconnect") started scheduling musb_irq_work with a delay of up to a second and with retries thereby making this easy to trigger, for example, by suspending shortly after a disconnect.

Note that we set a flag to prevent the irq work from rescheduling itself during suspend and instead process a disconnect immediately. This takes care of the case where we are disconnected shortly before suspending.

However, when in host mode, a disconnect while suspended will still go unnoticed and thus prevent the controller from runtime suspending upon resume as the session bit is always set. This will need to be addressed separately.

---
 drivers/usb/musb/musb_core.c | 11 +++++++++--
 drivers/usb/musb/musb_core.h |  2 ++
 2 files changed, 11 insertions(+), 2 deletions(-)

index 07b8c7152e3d..1ced3af75b05 100644
@@ -1861,7 +1861,7 @@ static void musb_pm_runtime_check_session(struct musb *musb)
 		MUSB_DEVCTL_HR;
 	switch (devctl & ~s) {
 	case MUSB_QUIRK_B_INVALID_VBUS_91:
-		if (musb->quirk_retries) {
+		if (musb->quirk_retries && !musb->flush_irq_work) {
 			musb_dbg(musb,
 				 "Poll devctl on invalid vbus, assume no session");
 			schedule_delayed_work(&musb->irq_work,

@@ -1871,7 +1871,7 @@ static void musb_pm_runtime_check_session(struct musb *musb)
 		}
 		/* fall through */
 	case MUSB_QUIRK_A_DISCONNECT_19:
-		if (musb->quirk_retries) {
+		if (musb->quirk_retries && !musb->flush_irq_work) {
 			musb_dbg(musb,
 				 "Poll devctl on possible host mode disconnect");
 			schedule_delayed_work(&musb->irq_work,

@@ -2681,8 +2681,15 @@ static int musb_suspend(struct device *dev)
 
 	musb_platform_disable(musb);
 	musb_disable_interrupts(musb);
+
+	musb->flush_irq_work = true;
+	while (flush_delayed_work(&musb->irq_work))
+		;
+	musb->flush_irq_work = false;
+
 	if (!(musb->io.quirks & MUSB_PRESERVE_SESSION))
 		musb_writeb(musb->mregs, MUSB_DEVCTL, 0);
+
 	WARN_ON(!list_empty(&musb->pending_list));
 
 	spin_lock_irqsave(&musb->lock, flags);

index c748f4ac1154..20f4614178d9 100644
@@ -428,6 +428,8 @@ struct musb {
 	unsigned		test_mode:1;
 	unsigned		softconnect:1;
 
+	unsigned		flush_irq_work:1;
+
 	u8			address;
 	u8			test_mode_nr;
 	u16			ackpend;		/* ep0 */

2.14.2