RDMA/qedr: Fix wmb usage in qedr
This patch comes as a result of Sinan Kaya's work and the decision that
writel() must be a strong enough barrier for DMA.
wmb usages in qedr driver have either been removed where they were there
only to order DMA accesses, and replaced with smp_wmb and comments for the
places that the barrier was there for SMP reasons.
Fixes: 561e5d48968b ("RDMA/qedr: eliminate duplicate barriers on weakly-ordered archs")
Signed-off-by: Michal Kalderon <Michal.Kalderon@cavium.com>
Signed-off-by: Ariel Elior <Ariel.Elior@cavium.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
diff --git a/drivers/infiniband/hw/qedr/verbs.c b/drivers/infiniband/hw/qedr/verbs.c
index 1835dc9..26a6989 100644
--- a/drivers/infiniband/hw/qedr/verbs.c
+++ b/drivers/infiniband/hw/qedr/verbs.c
@@ -804,8 +804,6 @@ static inline void qedr_init_cq_params(struct qedr_cq *cq,
static void doorbell_cq(struct qedr_cq *cq, u32 cons, u8 flags)
{
- /* Flush data before signalling doorbell */
- wmb();
cq->db.data.agg_flags = flags;
cq->db.data.value = cpu_to_le32(cons);
writeq(cq->db.raw, cq->db_addr);
@@ -1812,8 +1810,7 @@ static int qedr_update_qp_state(struct qedr_dev *dev,
*/
if (rdma_protocol_roce(&dev->ibdev, 1)) {
- wmb();
- writel_relaxed(qp->rq.db_data.raw, qp->rq.db);
+ writel(qp->rq.db_data.raw, qp->rq.db);
/* Make sure write takes effect */
mmiowb();
}
@@ -3198,9 +3195,16 @@ int qedr_post_send(struct ib_qp *ibqp, struct ib_send_wr *wr,
* vane. However this is not harmful (as long as the producer value is
* unchanged). For performance reasons we avoid checking for this
* redundant doorbell.
+ *
+ * qp->wqe_wr_id is accessed during qedr_poll_cq, as
+ * soon as we give the doorbell, we could get a completion
+ * for this wr, therefore we need to make sure that the
+ * memory is updated before giving the doorbell.
+ * During qedr_poll_cq, rmb is called before accessing the
+ * cqe. This covers for the smp_rmb as well.
*/
- wmb();
- writel_relaxed(qp->sq.db_data.raw, qp->sq.db);
+ smp_wmb();
+ writel(qp->sq.db_data.raw, qp->sq.db);
/* Make sure write sticks */
mmiowb();
@@ -3286,8 +3290,14 @@ int qedr_post_recv(struct ib_qp *ibqp, struct ib_recv_wr *wr,
qedr_inc_sw_prod(&qp->rq);
- /* Flush all the writes before signalling doorbell */
- wmb();
+ /* qp->rqe_wr_id is accessed during qedr_poll_cq, as
+ * soon as we give the doorbell, we could get a completion
+ * for this wr, therefore we need to make sure that the
+ * memory is update before giving the doorbell.
+ * During qedr_poll_cq, rmb is called before accessing the
+ * cqe. This covers for the smp_rmb as well.
+ */
+ smp_wmb();
qp->rq.db_data.data.value++;