Fix Xilinx SystemACE driver to handle empty CF slot

The SystemACE driver does not handle an empty CF slot gracefully. An
empty CF slot ends up hanging the system. This patch adds a check for
the CF state and stops trying to process requests if the slot is empty.
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

drivers/block/xsysace.c

@@ -489,6 +489,28 @@ static void ace_fsm_dostate(struct ace_device *ace)
 		ace->fsm_state, ace->id_req_count);
 #endif
 
+	/* Verify that there is actually a CF in the slot. If not, then
+	 * bail out back to the idle state and wake up all the waiters */
+	status = ace_in32(ace, ACE_STATUS);
+	if ((status & ACE_STATUS_CFDETECT) == 0) {
+		ace->fsm_state = ACE_FSM_STATE_IDLE;
+		ace->media_change = 1;
+		set_capacity(ace->gd, 0);
+		dev_info(ace->dev, "No CF in slot\n");
+
+		/* Drop all pending requests */
+		while ((req = elv_next_request(ace->queue)) != NULL)
+			end_request(req, 0);
+
+		/* Drop back to IDLE state and notify waiters */
+		ace->fsm_state = ACE_FSM_STATE_IDLE;
+		ace->id_result = -EIO;
+		while (ace->id_req_count) {
+			complete(&ace->id_completion);
+			ace->id_req_count--;
+		}
+	}
+
 	switch (ace->fsm_state) {
 	case ACE_FSM_STATE_IDLE:
 		/* See if there is anything to do */