How do I get more control with Displace modifier mesh and subdivision surface? I want to create 3d wall panel with deformer  


displacement modifier 
smooth with subdivision modifier


but when i use it all my mesh is broken like porridge. I need a flat bottom and the upper part must be changed from modifier. I used displacement ]2
Control your displacement modifier with a vertex group.  More to follow.

You can search here at BSE or other video sites for the easy process of creating a vertex group.  Essentially creating a vertex group in the [vertex group panel], selecting vertices and assigning weights by pressing the button in the panel.



In the image above a vertex group is created named [DisplaceGroup] and used as the vertex group name in the Displace modifier.  The vertex group is shown in [Edit Mode].  The yellow arrows show the relevant settings.

Note how the red area in the Edit Mode has weights of 1.0 and is affected by the Displace Modifier. The blue area has weights of 0.0 and is not affected by the displace modifier.  The use of the vertex group name makes this all function correctly.

This is guide for you to get quick results.  This is not a tutorial on vertex groups which are better demonstrated previously and elsewhere and can be found with a quick search.