Is there a way to create a package.xml contains all reports through Code.? I have tried listMetadata also, but could not create the xml with all the reports.
You can't use the "*" wildcard on Report metadata components so the answer above is inaccurate.
You have to list out each member with FolderName/ReportName for each. The article below from Salesforce's Metadata API guide speaks to more dynamic ways to accomplish this, but it's a little beyond my understanding at the moment.
<types> <members>*</members> <name>Reports</name> </types>