s390/qdio: let drivers opt-out from Output Queue scanning

If a driver wants to use the new Output Queue poll code, then the qdio
layer must disable its internal Queue scanning. Let the driver select
this mode by passing a special scan_threshold of 0.

As the scan_threshold is the same for all Output Queues, also move it
into the main qdio_irq struct. This allows for fast opt-out checking, a
driver is expected to operate either _all_ or none of its Output Queues
in polling mode.
Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Acked-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/s390/include/asm/qdio.h

@@ -359,7 +359,7 @@ struct qdio_initialize {
 	qdio_handler_t *output_handler;
 	void (**queue_start_poll_array) (struct ccw_device *, int,
 					  unsigned long);
-	int scan_threshold;
+	unsigned int scan_threshold;
 	unsigned long int_parm;
 	struct qdio_buffer **input_sbal_addr_array;
 	struct qdio_buffer **output_sbal_addr_array;

drivers/s390/cio/qdio.h

@@ -206,8 +206,6 @@ struct qdio_output_q {
 	struct qdio_outbuf_state *sbal_state;
 	/* timer to check for more outbound work */
 	struct timer_list timer;
-	/* used SBALs before tasklet schedule */
-	int scan_threshold;
 };
 
 /*
@@ -295,6 +293,7 @@ struct qdio_irq {
 	struct qdio_ssqd_desc ssqd_desc;
 	void (*orig_handler) (struct ccw_device *, unsigned long, struct irb *);
 
+	unsigned int scan_threshold;	/* used SBALs before tasklet schedule */
 	int perf_stat_enabled;
 
 	struct qdr *qdr;

drivers/s390/cio/qdio_main.c

@@ -880,7 +880,7 @@ static inline void qdio_check_outbound_pci_queues(struct qdio_irq *irq)
 	struct qdio_q *out;
 	int i;
 
-	if (!pci_out_supported(irq))
+	if (!pci_out_supported(irq) || !irq->scan_threshold)
 		return;
 
 	for_each_output_queue(irq, out, i)
@@ -973,7 +973,7 @@ static void qdio_int_handler_pci(struct qdio_irq *irq_ptr)
 		}
 	}
 
-	if (!pci_out_supported(irq_ptr))
+	if (!pci_out_supported(irq_ptr) || !irq_ptr->scan_threshold)
 		return;
 
 	for_each_output_queue(irq_ptr, q, i) {
@@ -1528,6 +1528,7 @@ static int handle_inbound(struct qdio_q *q, unsigned int callflags,
 static int handle_outbound(struct qdio_q *q, unsigned int callflags,
 			   int bufnr, int count)
 {
+	const unsigned int scan_threshold = q->irq_ptr->scan_threshold;
 	unsigned char state = 0;
 	int used, rc = 0;
 
@@ -1566,8 +1567,12 @@ static int handle_outbound(struct qdio_q *q, unsigned int callflags,
 		rc = qdio_kick_outbound_q(q, 0);
 	}
 
+	/* Let drivers implement their own completion scanning: */
+	if (!scan_threshold)
+		return rc;
+
 	/* in case of SIGA errors we must process the error immediately */
-	if (used >= q->u.out.scan_threshold || rc)
+	if (used >= scan_threshold || rc)
 		qdio_tasklet_schedule(q);
 	else
 		/* free the SBALs in case of no further traffic */

drivers/s390/cio/qdio_setup.c

@@ -248,7 +248,6 @@ static void setup_queues(struct qdio_irq *irq_ptr,
 		output_sbal_state_array += QDIO_MAX_BUFFERS_PER_Q;
 
 		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;
 
@@ -474,6 +473,7 @@ int qdio_setup_irq(struct qdio_initialize *init_data)
 	irq_ptr->nr_input_qs = init_data->no_input_qs;
 	irq_ptr->nr_output_qs = init_data->no_output_qs;
 	irq_ptr->cdev = init_data->cdev;
+	irq_ptr->scan_threshold = init_data->scan_threshold;
 	ccw_device_get_schid(irq_ptr->cdev, &irq_ptr->schid);
 	setup_queues(irq_ptr, init_data);