IB/ipath: Fix SDMA error recovery in absence of link status change

What's fixed:

    in ipath_cancel_sends()

        We need to unconditionally set ABORTING.  So, swap the tests
        so the set_bit() isn't shadowed by the &&.

        If we've disarmed the piobufs, then we need to unconditionally
        set DISARMED.  So, move it out from the overly protective if
        at the bottom.

    in sdma_abort_task()

        Abort_task was written knowing that the SDMA engine would always
        be reset (and restarted) on error.  A recent change broke that
        fundamental assumption by taking the restart portion and making
        it conditional on a link status change.  But, SDMA can go boom
        without a link status change in some conditions.

Signed-off-by: John Gregor <john.gregor@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/ipath/ipath_driver.c

@@ -1898,8 +1898,8 @@ void ipath_cancel_sends(struct ipath_devdata *dd, int restore_sendctrl)
 
 		spin_lock_irqsave(&dd->ipath_sdma_lock, flags);
 		skip_cancel =
-			!test_bit(IPATH_SDMA_DISABLED, statp) &&
-			test_and_set_bit(IPATH_SDMA_ABORTING, statp);
+			test_and_set_bit(IPATH_SDMA_ABORTING, statp)
+			&& !test_bit(IPATH_SDMA_DISABLED, statp);
 		spin_unlock_irqrestore(&dd->ipath_sdma_lock, flags);
 		if (skip_cancel)
 			goto bail;
@@ -1930,6 +1930,9 @@ void ipath_cancel_sends(struct ipath_devdata *dd, int restore_sendctrl)
 	ipath_disarm_piobufs(dd, 0,
 		dd->ipath_piobcnt2k + dd->ipath_piobcnt4k);
 
+	if (dd->ipath_flags & IPATH_HAS_SEND_DMA)
+		set_bit(IPATH_SDMA_DISARMED, &dd->ipath_sdma_status);
+
 	if (restore_sendctrl) {
 		/* else done by caller later if needed */
 		spin_lock_irqsave(&dd->ipath_sendctrl_lock, flags);
@@ -1949,7 +1952,6 @@ void ipath_cancel_sends(struct ipath_devdata *dd, int restore_sendctrl)
 		/* only wait so long for intr */
 		dd->ipath_sdma_abort_intr_timeout = jiffies + HZ;
 		dd->ipath_sdma_reset_wait = 200;
-		__set_bit(IPATH_SDMA_DISARMED, &dd->ipath_sdma_status);
 		if (!test_bit(IPATH_SDMA_SHUTDOWN, &dd->ipath_sdma_status))
 			tasklet_hi_schedule(&dd->ipath_sdma_abort_task);
 		spin_unlock_irqrestore(&dd->ipath_sdma_lock, flags);

drivers/infiniband/hw/ipath/ipath_sdma.c

@@ -308,13 +308,15 @@ static void sdma_abort_task(unsigned long opaque)
 		spin_unlock_irqrestore(&dd->ipath_sdma_lock, flags);
 
 		/*
-		 * Don't restart sdma here. Wait until link is up to ACTIVE.
-		 * VL15 MADs used to bring the link up use PIO, and multiple
-		 * link transitions otherwise cause the sdma engine to be
+		 * Don't restart sdma here (with the exception
+		 * below). Wait until link is up to ACTIVE.  VL15 MADs
+		 * used to bring the link up use PIO, and multiple link
+		 * transitions otherwise cause the sdma engine to be
 		 * stopped and started multiple times.
-		 * The disable is done here, including the shadow, so the
-		 * state is kept consistent.
-		 * See ipath_restart_sdma() for the actual starting of sdma.
+		 * The disable is done here, including the shadow,
+		 * so the state is kept consistent.
+		 * See ipath_restart_sdma() for the actual starting
+		 * of sdma.
 		 */
 		spin_lock_irqsave(&dd->ipath_sendctrl_lock, flags);
 		dd->ipath_sendctrl &= ~INFINIPATH_S_SDMAENABLE;
@@ -326,6 +328,13 @@ static void sdma_abort_task(unsigned long opaque)
 		/* make sure I see next message */
 		dd->ipath_sdma_abort_jiffies = 0;
 
+		/*
+		 * Not everything that takes SDMA offline is a link
+		 * status change.  If the link was up, restart SDMA.
+		 */
+		if (dd->ipath_flags & IPATH_LINKACTIVE)
+			ipath_restart_sdma(dd);
+
 		goto done;
 	}
 
@@ -427,7 +436,12 @@ int setup_sdma(struct ipath_devdata *dd)
 		goto done;
 	}
 
-	dd->ipath_sdma_status = 0;
+	/*
+	 * Set initial status as if we had been up, then gone down.
+	 * This lets initial start on transition to ACTIVE be the
+	 * same as restart after link flap.
+	 */
+	dd->ipath_sdma_status = IPATH_SDMA_ABORT_ABORTED;
 	dd->ipath_sdma_abort_jiffies = 0;
 	dd->ipath_sdma_generation = 0;
 	dd->ipath_sdma_descq_tail = 0;
@@ -618,6 +632,9 @@ void ipath_restart_sdma(struct ipath_devdata *dd)
 	ipath_read_kreg64(dd, dd->ipath_kregs->kr_scratch);
 	spin_unlock_irqrestore(&dd->ipath_sendctrl_lock, flags);
 
+	/* notify upper layers */
+	ipath_ib_piobufavail(dd->verbs_dev);
+
 bail:
 	return;
 }