[PATCH v4] s390/qdio: Ensure QDIO_IRQ_STATE_ACTIVE is set only after firmware activates.

[Nihar Panda <niharp@linux.ibm.com>]

Set QDIO_IRQ_STATE_ACTIVE only if both the subchannel-active bit and
the QDIO-active bit are set in the Subchannel Status Word (SCSW).

The channel subsystem sets the SCSW_ACTL_SCHACT bit in scsw.actl and
scsw.qact = 1 in the SCHIB to indicate that the activate-QDIO-queues
CCW program is running and the queues are ready.

An interrupt-driven approach is not applicable here.
Using CCW_FLAG_PCI on the activate CCW generates an intermediate interrupt
too early, before the firmware sets qact=1.
Therefore, polling the SCHIB via cio_update_schib() is the only way to
reliably detect when the queues are ready.

Signed-off-by: Nihar Panda <niharp@linux.ibm.com>
Reviewed-by: Alexandra Winter <wintera@linux.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Reviewed-by: Nagamani PV <nagamani@linux.ibm.com>
---
 arch/s390/include/asm/scsw.h |  4 +--
 drivers/s390/cio/qdio_main.c | 54 +++++++++++++++++++++++++++---------
 2 files changed, 43 insertions(+), 15 deletions(-)

diff --git a/arch/s390/include/asm/scsw.h b/arch/s390/include/asm/scsw.h
index 56003e26cdbf..bf00d827d72b 100644
--- a/arch/s390/include/asm/scsw.h
+++ b/arch/s390/include/asm/scsw.h
@@ -28,7 +28,7 @@
  * @zcc: zero condition code
  * @ectl: extended control
  * @pno: path not operational
- * @res: reserved
+ * @qact: qdio active
  * @fctl: function control
  * @actl: activity control
  * @stctl: status control
@@ -50,7 +50,7 @@ struct cmd_scsw {
 	__u32 zcc  : 1;
 	__u32 ectl : 1;
 	__u32 pno  : 1;
-	__u32 res  : 1;
+	__u32 qact : 1;
 	__u32 fctl : 3;
 	__u32 actl : 7;
 	__u32 stctl : 5;
diff --git a/drivers/s390/cio/qdio_main.c b/drivers/s390/cio/qdio_main.c
index c1e09fa34e77..821d501efdcc 100644
--- a/drivers/s390/cio/qdio_main.c
+++ b/drivers/s390/cio/qdio_main.c
@@ -1140,11 +1140,29 @@ EXPORT_SYMBOL_GPL(qdio_establish);
 /**
  * qdio_activate - activate queues on a qdio subchannel
  * @cdev: associated cdev
+ *
+ * This function must only be called when the QDIO subchannel is in
+ * QDIO_IRQ_STATE_ESTABLISHED state (i.e., after successful qdio_establish()).
+ * Any other state indicates either the subchannel is not ready or an error
+ * condition that requires proper recovery through qdio_shutdown() and
+ * qdio_establish() before activation can be attempted.
+ *
+ * Return:
+ * * 0		- success
+ * * -ENODEV	- device is not initialized
+ * * -EIO	- adapter lacks QDIO activation support, or
+ *                the IRQ state changed unexpectedly during activation
+ * * -EBUSY	- subchannel state is not QDIO_IRQ_STATE_ESTABLISHED
+ *                at call time
+ * * -ETIMEDOUT - subchannel failed to become active within the timeout
+ * * other	- standard error code forwarded from ccw_device_start()
  */
 int qdio_activate(struct ccw_device *cdev)
 {
+	struct subchannel *sch = to_subchannel(cdev->dev.parent);
 	struct qdio_irq *irq_ptr = cdev->private->qdio_data;
 	struct subchannel_id schid;
+	unsigned long timeout;
 	struct ciw *ciw;
 	int rc;
 
@@ -1161,7 +1179,8 @@ int qdio_activate(struct ccw_device *cdev)
 	}
 
 	mutex_lock(&irq_ptr->setup_mutex);
-	if (irq_ptr->state == QDIO_IRQ_STATE_INACTIVE) {
+	if (irq_ptr->state != QDIO_IRQ_STATE_ESTABLISHED) {
+		DBF_ERROR("%4x act WS:%d", schid.sch_no, irq_ptr->state);
 		rc = -EBUSY;
 		goto out;
 	}
@@ -1178,23 +1197,32 @@ int qdio_activate(struct ccw_device *cdev)
 			      0, DOIO_DENY_PREFETCH);
 	spin_unlock_irq(get_ccwdev_lock(cdev));
 	if (rc) {
-		DBF_ERROR("%4x act IO ERR", irq_ptr->schid.sch_no);
-		DBF_ERROR("rc:%4x", rc);
+		DBF_ERROR("%4x act IE:%d", irq_ptr->schid.sch_no, rc);
 		goto out;
 	}
 
-	/* wait for subchannel to become active */
-	msleep(5);
+	rc = -ETIMEDOUT;
+	timeout = jiffies + HZ;
 
-	switch (irq_ptr->state) {
-	case QDIO_IRQ_STATE_STOPPED:
-	case QDIO_IRQ_STATE_ERR:
-		rc = -EIO;
-		break;
-	default:
-		qdio_set_state(irq_ptr, QDIO_IRQ_STATE_ACTIVE);
-		rc = 0;
+	while (time_before(jiffies, timeout)) {
+		msleep(1);
+		if (irq_ptr->state != QDIO_IRQ_STATE_ESTABLISHED) {
+			rc = -EIO;
+			DBF_ERROR("%4x act WS:%d", irq_ptr->schid.sch_no, irq_ptr->state);
+			break;
+		}
+		/* Query hardware */
+		if (cio_update_schib(sch) == 0) {
+			if ((sch->schib.scsw.cmd.actl & SCSW_ACTL_SCHACT)
+					&& sch->schib.scsw.cmd.qact) {
+				qdio_set_state(irq_ptr, QDIO_IRQ_STATE_ACTIVE);
+				rc = 0;
+				break;
+			}
+		}
 	}
+	if (rc == -ETIMEDOUT)
+		DBF_ERROR("%4x act TIMEOUT", irq_ptr->schid.sch_no);
 out:
 	mutex_unlock(&irq_ptr->setup_mutex);
 	return rc;
-- 
2.53.0