Solved by albanD in post #9 
              
              
                Convolution is a linear operation. So you can see it as (ignoring conv parameters): y = conv(x ,w). 
Then dL/dx = dL/dy dy/dx = conv_transpose(dL/dy, w) and dL/dw = dL/dy dy/dw = conv(x, dL/dy). These new conv with modified parameters. 
The way I check if the output is needed is by checking this fil…