net/mlx5: Remove spinlock support from mlx5_write64

As there is no user of mlx5_write64 that passes a spinlock to
mlx5_write64, remove this functionality and simplify the function.

Signed-off-by: Maxim Mikityanskiy <[e-mail]>
Reviewed-by: Eran Ben Elisha <[e-mail]>
Signed-off-by: Saeed Mahameed <[e-mail]>

drivers/infiniband/hw/mlx5/qp.c

···
 		wmb();
 
 		/* currently we support only regular doorbells */
-		mlx5_write64((__be32 *)ctrl, bf->bfreg->map + bf->offset, NULL);
+		mlx5_write64((__be32 *)ctrl, bf->bfreg->map + bf->offset);
 		/* Make sure doorbells don't leak out of SQ spinlock
 		 * and reach the HCA out of order.
 		 */

drivers/net/ethernet/mellanox/mlx5/core/en.h

···
 	 */
 	wmb();
 
-	mlx5_write64((__be32 *)ctrl, uar_map, NULL);
+	mlx5_write64((__be32 *)ctrl, uar_map);
 }
 
 static inline void mlx5e_cq_arm(struct mlx5e_cq *cq)

drivers/net/ethernet/mellanox/mlx5/core/fpga/conn.c

···
 	*conn->qp.wq.sq.db = cpu_to_be32(conn->qp.sq.pc);
 	/* Make sure that doorbell record is visible before ringing */
 	wmb();
-	mlx5_write64(wqe, conn->fdev->conn_res.uar->map + MLX5_BF_OFFSET, NULL);
+	mlx5_write64(wqe, conn->fdev->conn_res.uar->map + MLX5_BF_OFFSET);
 }
 
 static void mlx5_fpga_conn_post_send(struct mlx5_fpga_conn *conn,

include/linux/mlx5/cq.h

···
 	doorbell[0] = cpu_to_be32(sn << 28 | cmd | ci);
 	doorbell[1] = cpu_to_be32(cq->cqn);
 
-	mlx5_write64(doorbell, uar_page + MLX5_CQ_DOORBELL, NULL);
+	mlx5_write64(doorbell, uar_page + MLX5_CQ_DOORBELL);
 }
 
 static inline void mlx5_cq_hold(struct mlx5_core_cq *cq)

include/linux/mlx5/doorbell.h

···
 #define MLX5_BF_OFFSET	      0x800
 #define MLX5_CQ_DOORBELL      0x20
 
-#if BITS_PER_LONG == 64
 /* Assume that we can just write a 64-bit doorbell atomically.  s390
  * actually doesn't have writeq() but S/390 systems don't even have
  * PCI so we won't worry about it.
+ *
+ * Note that the write is not atomic on 32-bit systems! In contrast to 64-bit
+ * ones, it requires proper locking. mlx5_write64 doesn't do any locking, so use
+ * it at your own discretion, protected by some kind of lock on 32 bits.
+ *
+ * TODO: use write{q,l}_relaxed()
  */
 
-static inline void mlx5_write64(__be32 val[2], void __iomem *dest,
-				spinlock_t *doorbell_lock)
+static inline void mlx5_write64(__be32 val[2], void __iomem *dest)
 {
+#if BITS_PER_LONG == 64
 	__raw_writeq(*(u64 *)val, dest);
-}
-
 #else
-
-/* Just fall back to a spinlock to protect the doorbell if
- * BITS_PER_LONG is 32 -- there's no portable way to do atomic 64-bit
- * MMIO writes.
- */
-
-static inline void mlx5_write64(__be32 val[2], void __iomem *dest,
-				spinlock_t *doorbell_lock)
-{
-	unsigned long flags;
-
-	if (doorbell_lock)
-		spin_lock_irqsave(doorbell_lock, flags);
 	__raw_writel((__force u32) val[0], dest);
 	__raw_writel((__force u32) val[1], dest + 4);
-	if (doorbell_lock)
-		spin_unlock_irqrestore(doorbell_lock, flags);
-}
-
 #endif
+}
 
 #endif /* MLX5_DOORBELL_H */