How to build or tune topi operator

I want to build topi conv, so I wrote such code

input_shape=(1, 3, 224, 224)
filter_shape=(10, 3, 5, 5)
strides=(1, 1)
paddings=(2, 2)
dilations=(1, 1)

A = te.placeholder(input_shape)
W = te.placeholder(filter_shape)

    C = topi.nn.conv2d_nchw(A, W, strides, paddings, dilations)
    s = topi.cuda.schedule_conv2d_nchw(C)
    func =, [A, W, C])


and I got such error

RuntimeError  Traceback (most recent call last)
     10 with"cuda"):
     11     C = topi.nn.conv2d_nchw(A, W, strides, paddings, dilations)
---> 12     s = topi.cuda.schedule_conv2d_nchw(C)
     13     func =, [A, W, C])

/opt/apache-tvm-src-v0.10.0/python/tvm/autotvm/task/ in wrapper(outs, *args, **kwargs)
    235             if workload is None:
    236                 raise RuntimeError(
--> 237                     f"Cannot find TOPI workload {task_name}. "
    238                     "Is it registered with `register_topi_compute`?"
    239                 )

RuntimeError: Cannot find TOPI workload conv2d_nchw.cuda. Is it registered with `register_topi_compute`?

but this bug disappeared when I changed topi.nn.conv2d_nchw to topi.cuda.conv2d_nchw. I’m new to tvm so I don’t really know the difference between the two api. I try to find answer in tvm doc, but I can’t find any information about topi.cuda.conv2d_nchw and topi.cuda.schedule_xxx

Can someone tell me the answer?Besides, I really want to know if I want to use topi, do I need autotvm to tune it?In my shallow knowledge, topi should be something with schedule template for autotvm, and the final code need to be tuned.