drivers: Remove explicit invocations of mmiowb()

mmiowb() is now implied by spin_unlock() on architectures that require
it, so there is no reason to call it from driver code. This patch was
generated using coccinelle:

	@mmiowb@
	@@
	- mmiowb();

and invoked as:

$ for d in drivers include/linux/qed sound; do \
spatch --include-headers --sp-file mmiowb.cocci --dir $d --in-place; done

NOTE: mmiowb() has only ever guaranteed ordering in conjunction with
spin_unlock(). However, pairing each mmiowb() removal in this patch with
the corresponding call to spin_unlock() is not at all trivial, so there
is a small chance that this change may regress any drivers incorrectly
relying on mmiowb() to order MMIO writes between CPUs using lock-free
synchronisation. If you've ended up bisecting to this commit, you can
reintroduce the mmiowb() calls using wmb() instead, which should restore
the old behaviour on all architectures other than some esoteric ia64
systems.

Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

drivers/infiniband/hw/mthca/mthca_cmd.c

@@ -292,12 +292,6 @@ static int mthca_cmd_post(struct mthca_dev *dev,
 		err = mthca_cmd_post_hcr(dev, in_param, out_param, in_modifier,
 					 op_modifier, op, token, event);
 
-	/*
-	 * Make sure that our HCR writes don't get mixed in with
-	 * writes from another CPU starting a FW command.
-	 */
-	mmiowb();
-
 	mutex_unlock(&dev->cmd.hcr_mutex);
 	return err;
 }

drivers/infiniband/hw/mthca/mthca_cq.c

@@ -211,11 +211,6 @@ static inline void update_cons_index(struct mthca_dev *dev, struct mthca_cq *cq,
 		mthca_write64(MTHCA_TAVOR_CQ_DB_INC_CI | cq->cqn, incr - 1,
 			      dev->kar + MTHCA_CQ_DOORBELL,
 			      MTHCA_GET_DOORBELL_LOCK(&dev->doorbell_lock));
-		/*
-		 * Make sure doorbells don't leak out of CQ spinlock
-		 * and reach the HCA out of order:
-		 */
-		mmiowb();
 	}
 }
 

drivers/infiniband/hw/mthca/mthca_qp.c

@@ -1809,11 +1809,6 @@ out:
 			      (qp->qpn << 8) | size0,
 			      dev->kar + MTHCA_SEND_DOORBELL,
 			      MTHCA_GET_DOORBELL_LOCK(&dev->doorbell_lock));
-		/*
-		 * Make sure doorbells don't leak out of SQ spinlock
-		 * and reach the HCA out of order:
-		 */
-		mmiowb();
 	}
 
 	qp->sq.next_ind = ind;
@@ -1924,12 +1919,6 @@ out:
 	qp->rq.next_ind = ind;
 	qp->rq.head    += nreq;
 
-	/*
-	 * Make sure doorbells don't leak out of RQ spinlock and reach
-	 * the HCA out of order:
-	 */
-	mmiowb();
-
 	spin_unlock_irqrestore(&qp->rq.lock, flags);
 	return err;
 }
@@ -2164,12 +2153,6 @@ out:
 			      MTHCA_GET_DOORBELL_LOCK(&dev->doorbell_lock));
 	}
 
-	/*
-	 * Make sure doorbells don't leak out of SQ spinlock and reach
-	 * the HCA out of order:
-	 */
-	mmiowb();
-
 	spin_unlock_irqrestore(&qp->sq.lock, flags);
 	return err;
 }

drivers/infiniband/hw/mthca/mthca_srq.c

@@ -570,12 +570,6 @@ int mthca_tavor_post_srq_recv(struct ib_srq *ibsrq, const struct ib_recv_wr *wr,
 			      MTHCA_GET_DOORBELL_LOCK(&dev->doorbell_lock));
 	}
 
-	/*
-	 * Make sure doorbells don't leak out of SRQ spinlock and
-	 * reach the HCA out of order:
-	 */
-	mmiowb();
-
 	spin_unlock_irqrestore(&srq->lock, flags);
 	return err;
 }