How to update a ag-grid child component in parent component

I create a ag-grid in a child component, when the rowData have been updated in child component, how can the parent copmonent be updated to see the new grid data?

child.html

<ag-grid-angular  ...></ag-grid-angular>

parent.html

<div> some other content</div>
<div>
    <child></child>
</div>

Thanks for your help~