cxgb4: DB Drop Recovery for RDMA and LLD queues

recover LLD EQs for DB drop interrupts.  This includes adding a new
db_lock, a spin lock disabling BH too, used by the recovery thread and
the ring_tx_db() paths to allow db drop recovery.

Clean up initial DB avoidance code.

Add read_eq_indices() - this allows the LLD to use the PCIe mw to
efficiently read hw eq contexts.

Add cxgb4_sync_txq_pidx() - called by iw_cxgb4 to sync up the sw/hw
pidx value.

Add flush_eq_cache() and cxgb4_flush_eq_cache().  This allows iw_cxgb4
to flush the sge eq context cache before beginning db drop recovery.

Add module parameter, dbfoifo_int_thresh, to allow tuning the db
interrupt threshold value.

Add dbfifo_int_thresh to cxgb4_lld_info so iw_cxgb4 knows the threshold.

Add module parameter, dbfoifo_drain_delay, to allow tuning the amount
of time delay between DB FULL and EMPTY upcalls to iw_cxgb4.

Signed-off-by: Vipul Pandya <vipul@chelsio.com>
Signed-off-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

1 files changed, 16 insertions, 4 deletions

diff --git a/drivers/net/ethernet/chelsio/cxgb4/sge.c b/drivers/net/ethernet/chelsio/cxgb4/sge.c
index 234c157a4879..e111d974afd8 100644
--- a/drivers/net/ethernet/chelsio/cxgb4/sge.c
+++ b/drivers/net/ethernet/chelsio/cxgb4/sge.c
@@ -767,8 +767,13 @@ static void write_sgl(const struct sk_buff *skb, struct sge_txq *q,
 static inline void ring_tx_db(struct adapter *adap, struct sge_txq *q, int n)
 {
 	wmb();            /* write descriptors before telling HW */
-	t4_write_reg(adap, MYPF_REG(SGE_PF_KDOORBELL),
-		     QID(q->cntxt_id) | PIDX(n));
+	spin_lock(&q->db_lock);
+	if (!q->db_disabled) {
+		t4_write_reg(adap, MYPF_REG(A_SGE_PF_KDOORBELL),
+			     V_QID(q->cntxt_id) | V_PIDX(n));
+	}
+	q->db_pidx = q->pidx;
+	spin_unlock(&q->db_lock);
 }
 
 /**
@@ -2081,6 +2086,7 @@ static void init_txq(struct adapter *adap, struct sge_txq *q, unsigned int id)
 	q->stops = q->restarts = 0;
 	q->stat = (void *)&q->desc[q->size];
 	q->cntxt_id = id;
+	spin_lock_init(&q->db_lock);
 	adap->sge.egr_map[id - adap->sge.egr_start] = q;
 }
 
@@ -2415,9 +2421,15 @@ void t4_sge_init(struct adapter *adap)
 			 RXPKTCPLMODE |
 			 (STAT_LEN == 128 ? EGRSTATUSPAGESIZE : 0));
 
+	/*
+	 * Set up to drop DOORBELL writes when the DOORBELL FIFO overflows
+	 * and generate an interrupt when this occurs so we can recover.
+	 */
 	t4_set_reg_field(adap, A_SGE_DBFIFO_STATUS,
-			V_HP_INT_THRESH(5) | V_LP_INT_THRESH(5),
-			V_HP_INT_THRESH(5) | V_LP_INT_THRESH(5));
+			V_HP_INT_THRESH(M_HP_INT_THRESH) |
+			V_LP_INT_THRESH(M_LP_INT_THRESH),
+			V_HP_INT_THRESH(dbfifo_int_thresh) |
+			V_LP_INT_THRESH(dbfifo_int_thresh));
 	t4_set_reg_field(adap, A_SGE_DOORBELL_CONTROL, F_ENABLE_DROP,
 			F_ENABLE_DROP);