s390/qdio: add IRQ reduction for error SBALs

SBALs in PRIMED or ERROR state represent new work on the Input Queue.
But while inbound_primed() does all sorts of ACK management for new
PRIMED work, the same handling is currently missing for ERROR work.
In particular the path for ERROR work doesn't clear up _old_ ACKs.

Treat ERROR work the same as PRIMED work, but consider that the QEBSM
auto-ACK feature doesn't apply here. So we need to set the ACK manually,
as if it was a non-QEBSM device.

Note that this doesn't aspire to actually improve performance, the main
goal is to just unify the code paths and have consistent behaviour.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

diff --git a/drivers/s390/cio/qdio_main.c b/drivers/s390/cio/qdio_main.c
index eea3032e68c0b6bfe02e619776c688a4a1ef6cf9..f5596265b053eb96bed6aaec44b18c872348c59d 100644 (file)
--- a/drivers/s390/cio/qdio_main.c
+++ b/drivers/s390/cio/qdio_main.c
@@ -438,15 +438,12 @@ static void process_buffer_error(struct qdio_q *q, unsigned int start,
                  q->sbal[start]->element[15].sflags);
 }
 
-static inline void inbound_primed(struct qdio_q *q, unsigned int start,
-                                 int count)
+static inline void inbound_handle_work(struct qdio_q *q, unsigned int start,
+                                      int count, bool auto_ack)
 {
        int new;
 
-       DBF_DEV_EVENT(DBF_INFO, q->irq_ptr, "in prim:%1d %02x", q->nr, count);
-
-       /* for QEBSM the ACK was already set by EQBS */
-       if (is_qebsm(q)) {
+       if (auto_ack) {
                if (!q->u.in.ack_count) {
                        q->u.in.ack_count = count;
                        q->u.in.ack_start = start;
@@ -507,19 +504,21 @@ static int get_inbound_buffer_frontier(struct qdio_q *q, unsigned int start)
 
        switch (state) {
        case SLSB_P_INPUT_PRIMED:
-               inbound_primed(q, start, count);
+               DBF_DEV_EVENT(DBF_INFO, q->irq_ptr, "in prim:%1d %02x", q->nr,
+                             count);
+
+               inbound_handle_work(q, start, count, is_qebsm(q));
                if (atomic_sub_return(count, &q->nr_buf_used) == 0)
                        qperf_inc(q, inbound_queue_full);
                if (q->irq_ptr->perf_stat_enabled)
                        account_sbals(q, count);
                return count;
        case SLSB_P_INPUT_ERROR:
+               DBF_DEV_EVENT(DBF_INFO, q->irq_ptr, "in err:%1d %02x", q->nr,
+                             count);
+
                process_buffer_error(q, start, count);
-               /*
-                * Interrupts may be avoided as long as the error is present
-                * so change the buffer state immediately to avoid starvation.
-                */
-               set_buf_states(q, start, SLSB_P_INPUT_NOT_INIT, count);
+               inbound_handle_work(q, start, count, false);
                if (atomic_sub_return(count, &q->nr_buf_used) == 0)
                        qperf_inc(q, inbound_queue_full);
                if (q->irq_ptr->perf_stat_enabled)