[S390] qdio: outbound tasklet scan threshold

Introduce a scan treshold for the qdio outbound queues. By setting the
threshold the driver can tell qdio after how much used SBALs qdio
should schedule the outbound tasklet that scans the queue for finished
SBALs. The threshold is specific by the drivers because a
Hipersockets device is much faster in utilizing outbound buffers than a
ZFCP or OSA device.

The default values after how many used SBALs the tasklet should run are:

OSA:          > 31 SBALs
Hipersockets: > 7 SBALs
zfcp:         > 55 SBALs
Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/qdio.h

@@ -361,6 +361,7 @@ struct qdio_initialize {
 	qdio_handler_t *input_handler;
 	qdio_handler_t *output_handler;
 	void (*queue_start_poll) (struct ccw_device *, int, unsigned long);
+	int scan_threshold;
 	unsigned long int_parm;
 	void **input_sbal_addr_array;
 	void **output_sbal_addr_array;

drivers/s390/cio/qdio.h

@@ -249,6 +249,8 @@ struct qdio_output_q {
 	int use_enh_siga;
 	/* timer to check for more outbound work */
 	struct timer_list timer;
+	/* used SBALs before tasklet schedule */
+	int scan_threshold;
 };
 
 /*

drivers/s390/cio/qdio_main.c

@@ -1492,7 +1492,13 @@ static int handle_outbound(struct qdio_q *q, unsigned int callflags,
 		qperf_inc(q, fast_requeue);
 
 out:
-	tasklet_schedule(&q->tasklet);
+	/* in case of SIGA errors we must process the error immediately */
+	if (used >= q->u.out.scan_threshold || rc)
+		tasklet_schedule(&q->tasklet);
+	else
+		/* free the SBALs in case of no further traffic */
+		if (!timer_pending(&q->u.out.timer))
+			mod_timer(&q->u.out.timer, jiffies + HZ);
 	return rc;
 }
 

drivers/s390/cio/qdio_setup.c

@@ -178,6 +178,7 @@ static void setup_queues(struct qdio_irq *irq_ptr,
 		setup_queues_misc(q, irq_ptr, qdio_init->output_handler, i);
 
 		q->is_input_q = 0;
+		q->u.out.scan_threshold = qdio_init->scan_threshold;
 		setup_storage_lists(q, irq_ptr, output_sbal_array, i);
 		output_sbal_array += QDIO_MAX_BUFFERS_PER_Q;
 

drivers/s390/net/qeth_core_main.c

@@ -3831,6 +3831,8 @@ static int qeth_qdio_establish(struct qeth_card *card)
 	init_data.int_parm               = (unsigned long) card;
 	init_data.input_sbal_addr_array  = (void **) in_sbal_ptrs;
 	init_data.output_sbal_addr_array = (void **) out_sbal_ptrs;
+	init_data.scan_threshold =
+		(card->info.type == QETH_CARD_TYPE_IQD) ? 8 : 32;
 
 	if (atomic_cmpxchg(&card->qdio.state, QETH_QDIO_ALLOCATED,
 		QETH_QDIO_ESTABLISHED) == QETH_QDIO_ALLOCATED) {

drivers/s390/scsi/zfcp_qdio.c

@@ -292,6 +292,8 @@ static void zfcp_qdio_setup_init_data(struct qdio_initialize *id,
 	id->int_parm = (unsigned long) qdio;
 	id->input_sbal_addr_array = (void **) (qdio->res_q);
 	id->output_sbal_addr_array = (void **) (qdio->req_q);
+	id->scan_threshold =
+		QDIO_MAX_BUFFERS_PER_Q - ZFCP_QDIO_MAX_SBALS_PER_REQ * 2;
 }
 
 /**