musb_gadget: Fix for spurious interrupts on endpoint zero.

There is a multi-year old bug in the MUSB hardware which is not documented.
It causes spurious interrupts and have various symptoms, like endless
"SetupEnd came in a wrong ep0stage" messages. The fix is taken from the
FreeBSD's musb driver.

How to reproduce:
For example issue clear-stall on a couple of endpoints very fast,
like one request per 125us. After a while the bug triggers and the
musb-chip becomes unusable until next re-enumeration.

Signed-off-by: Hans Petter Selasky <hps@bitfrost.no>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/musb/musb_gadget_ep0.c b/drivers/usb/musb/musb_gadget_ep0.c
index 9378b359c1f012d6abcacd358b7366bcafb32912..6a0d0467ec748131b7cbcd505fd3fce2497e2bbe 100644 (file)
--- a/drivers/usb/musb/musb_gadget_ep0.c
+++ b/drivers/usb/musb/musb_gadget_ep0.c
@@ -679,6 +679,14 @@ irqreturn_t musb_g_ep0_irq(struct musb *musb)
                        musb_readb(mbase, MUSB_FADDR),
                        decode_ep0stage(musb->ep0_state));
 
+       if (csr & MUSB_CSR0_P_DATAEND) {
+               /*
+                * If DATAEND is set we should not call the callback,
+                * hence the status stage is not complete.
+                */
+               return IRQ_HANDLED;
+       }
+
        /* I sent a stall.. need to acknowledge it now.. */
        if (csr & MUSB_CSR0_P_SENTSTALL) {
                musb_writew(regs, MUSB_CSR0,