mlx4_core: Fix fallback from MSI-X to INTx

The test in mlx4_load_one() to remove MLX4_FLAG_MSI_X expects mlx4_NOP() to
fail with -EBUSY. It is also necessary to avoid the reset since the device
is not fully reinitialized before calling mlx4_start_hca() a second time.

Note that this will also affect mlx4_test_interrupts(), the only other user
of MLX4_CMD_NOP.

Fixes: f5aef5aa ("net/mlx4_core: Activate reset flow upon fatal command cases")
Signed-off-by: Benjamin Poirier <bpoirier@suse.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/cmd.c

@@ -714,8 +714,13 @@ static int mlx4_cmd_wait(struct mlx4_dev *dev, u64 in_param, u64 *out_param,
 					 msecs_to_jiffies(timeout))) {
 		mlx4_warn(dev, "command 0x%x timed out (go bit not cleared)\n",
 			  op);
-		err = -EIO;
-		goto out_reset;
+		if (op == MLX4_CMD_NOP) {
+			err = -EBUSY;
+			goto out;
+		} else {
+			err = -EIO;
+			goto out_reset;
+		}
 	}
 
 	err = context->result;