@dkumar,
To make markers to be completely visible you can set the axis-Y maximum to the maximum Y value of the datapoints plus half the marker size as shown in the code snippet below.
chart.axisY[0].set("maximum", chart.axisY[0].convertPixelToValue(chart.axisY[0].convertValueToPixel(chart.axisY[0].get("maximum")) - chart.data[0].get("markerSize")/2));
Kindly refer to the updated JSFiddle for complete working example.
__
Sachin Bisht
Team CanvasJS