Add a spin lock that prevents the sequencer from attempting to add an

entry to the QOUTFIFO when it is full.  This should eliminate the
"Timed out while idle" problems that many have reported.

In truth, this is somewhat of a hack.  Although are interrupt latency is
low enough that we should be able to always service the queue in time,
since each entry must be passed up to the higher SCSI layer for what can
be a large amount of processing (perhaps even resulting in a new command
being queued) with interrupts disabled, we need this mechanism to avoid
overflow.  In the future, these additional tasks will be offloaded to a
software interrupt handler which should make this hack unnecessary.

2 files changed, 26 insertions, 2 deletions

diff --git a/sys/dev/aic7xxx/aic7xxx.reg b/sys/dev/aic7xxx/aic7xxx.reg
index fabef19..6ecae3b 100644
--- a/sys/dev/aic7xxx/aic7xxx.reg
+++ b/sys/dev/aic7xxx/aic7xxx.reg
@@ -35,7 +35,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: aic7xxx.reg,v 1.3 1997/04/24 16:52:16 gibbs Exp $
+ *	$Id: aic7xxx.reg,v 1.4 1997/06/27 19:38:39 gibbs Exp $
  */
 
 /*
@@ -1079,6 +1079,21 @@ scratch_ram {
 	CUR_SCBID {
 		size		1
 	}
+	/*
+	 * Running count of commands placed in
+	 * the QOUTFIFO.  This is cleared by the
+	 * kernel driver every FIFODEPTH commands.
+	 */
+	CMDOUTCNT {
+		size		1
+	}
+	/*
+	 * Maximum number of entries allowed in
+	 * the QOUT/INFIFO.
+	 */
+	FIFODEPTH {
+		size		1
+	}
 	ARG_1 {
 		size		1
 		mask	SEND_MSG	0x80
diff --git a/sys/dev/aic7xxx/aic7xxx.seq b/sys/dev/aic7xxx/aic7xxx.seq
index 3c2d89c..d6b6a04 100644
--- a/sys/dev/aic7xxx/aic7xxx.seq
+++ b/sys/dev/aic7xxx/aic7xxx.seq
@@ -35,7 +35,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	$Id: aic7xxx.seq,v 1.73 1997/04/24 16:52:18 gibbs Exp $
+ *	$Id: aic7xxx.seq,v 1.74 1997/06/27 19:38:42 gibbs Exp $
  */
 
 #include <dev/aic7xxx/aic7xxx.reg>
@@ -643,6 +643,15 @@ status_ok:
 
 complete:
 	/* Post the SCB and issue an interrupt */
+.if ( SCB_PAGING )
+	/*
+	 * Spin loop until there is space
+	 * in the QOUTFIFO.
+	 */
+	mov	A, FIFODEPTH;
+	cmp	CMDOUTCNT, A	je .;
+	inc	CMDOUTCNT;
+.endif
 	mov	QOUTFIFO,SCB_TAG;
 	mvi	INTSTAT,CMDCMPLT;
 	test	SCB_CONTROL, ABORT_SCB jz dma_next_scb;