How to repeat automatically seamless pattern in Photoshop?

Let's say I already have a seamless pattern. For example this one:

I'd like to quickly repeat it 4 times.

So the result would be:

Is there any automated way to do this in Photoshop, instead of resizing the workspace then copying and placing it three more times?

Answer

Well you can actually make it a pattern in Photoshop.

With the tile open, select all and choose Edit > Define Pattern. Then it's a pattern just like all the other built in Photoshop patterns.

If you know the tile size you can create a new document the size of 4 tiles, then just apply a pattern fill layer.

With a 500x500px tile, create a 1000x1000px document and choose Layer > New Fill Layer > Pattern... selecting your pattern.

If you don't know the tile size, and it's already a pattern in Photoshop... You can turn on Tool Tips in the Preferences, then hover your mouse over a pattern and the tip will show you the tile size: