On Mon, Mar 19, 2018 at 10:47:44PM -0400, Sinan Kaya wrote: > Code includes wmb() followed by writel(). writel() already has a barrier on > some architectures like arm64. > > This ends up CPU observing two barriers back to back before executing the > register write. > > Since code already has an explicit barrier call, changing writel() to > writel_relaxed(). > > Signed-off-by: Sinan Kaya <[email protected]> > --- > drivers/infiniband/hw/mlx4/qp.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-)
Reviewed-by: Jason Gunthorpe <[email protected]> > diff --git a/drivers/infiniband/hw/mlx4/qp.c b/drivers/infiniband/hw/mlx4/qp.c > index f045491..74b27b0 100644 > --- a/drivers/infiniband/hw/mlx4/qp.c > +++ b/drivers/infiniband/hw/mlx4/qp.c > @@ -3880,8 +3880,8 @@ int mlx4_ib_post_send(struct ib_qp *ibqp, struct > ib_send_wr *wr, > */ > wmb(); > > - writel(qp->doorbell_qpn, > - to_mdev(ibqp->device)->uar_map + MLX4_SEND_DOORBELL); > + writel_relaxed(qp->doorbell_qpn, > + to_mdev(ibqp->device)->uar_map + MLX4_SEND_DOORBELL); > > /* > * Make sure doorbells don't leak out of SQ spinlock > -- > 2.7.4 >
