[PATCH linux dev-4.10 v2] drivers (fsi): sbefifo: Add timeout for waiting for data

[Eddie James]

From: "Edward A. James" <eajames at us.ibm.com>

During a transfer, in the event that the SBE isn't running, the driver
will wait for data to appear in the FIFO forever. This doesn't work at
BMC boot time if any transfers are attempted (by OCC driver probing, for
example), as it will just hang the boot. So add a simple timeout
mechanism when the driver reschdules waiting for data to show up in the
FIFO.

Tested on witherspoon by rebooting the BMC successfully with chassis
power on.

Signed-off-by: Edward A. James <eajames at us.ibm.com>
---
Changes since v1:
 * Reset the wait_data_timeout field if we get data. If we get data, the SBE
   is running and we really shouldn't timeout.

 drivers/fsi/fsi-sbefifo.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/drivers/fsi/fsi-sbefifo.c b/drivers/fsi/fsi-sbefifo.c
index f756822..41b838e 100644
--- a/drivers/fsi/fsi-sbefifo.c
+++ b/drivers/fsi/fsi-sbefifo.c
@@ -54,6 +54,7 @@
 #define SBEFIFO_EOT_ACK		0x14
 
 #define SBEFIFO_RESCHEDULE	msecs_to_jiffies(500)
+#define SBEFIFO_MAX_RESCHDULE	msecs_to_jiffies(5000)
 
 struct sbefifo {
 	struct timer_list poll_timer;
@@ -77,6 +78,7 @@ struct sbefifo_buf {
 };
 
 struct sbefifo_xfr {
+	unsigned long wait_data_timeout;
 	struct sbefifo_buf *rbuf;
 	struct sbefifo_buf *wbuf;
 	struct list_head client;
@@ -450,11 +452,27 @@ static void sbefifo_poll_timer(unsigned long data)
 
 		devn = sbefifo_dev_nwreadable(sts);
 		if (devn == 0) {
+			/*
+			 * Limit the maximum waiting period for data in the
+			 * FIFO. If the SBE isn't running, we will wait
+			 * forever.
+			 */
+			if (!xfr->wait_data_timeout) {
+				xfr->wait_data_timeout =
+					jiffies + SBEFIFO_MAX_RESCHDULE;
+			} else if (time_after(jiffies,
+					      xfr->wait_data_timeout)) {
+				ret = -ETIME;
+				goto out;
+			}
+
 			/* No data yet.  Reschedule. */
 			sbefifo->poll_timer.expires = jiffies +
 				SBEFIFO_RESCHEDULE;
 			add_timer(&sbefifo->poll_timer);
 			goto out_unlock;
+		} else {
+			xfr->wait_data_timeout = 0;
 		}
 
 		/* Fill.  The EOT word is discarded.  */
-- 
1.8.3.1