This article will document the process of making OpenWRT work on the DIR-615 rev. A1.
In its dmesg, the stock firmware reports this board as "Marvell Development Board (LSP Version 0.0.102)-- RD-88F5181L-VOIP-FE".
In the GPL'd source code available from D-Link [FTP], in DIR-615A1-GPL.tgz (inside the downloaded file), in Noahsark/platform/MVL5181/linux/arch/arm/mach-mv88fxx81/Board/boardEnv/DB_88FXX81/mvBoardEnvSpec.h, a search for "RD-88F5181L-VOIP-FE" reveals a list of constants that pertain to the board. (See attached .XLS file)
I created Board ID# 4262 at the ARM Linux website to describe this board.(This document from Nas-Central.org explains why this needs to be done, and goes into detail about how to get support for your particular Orion board type in the mainline Linux kernel. This only ever needs to be done once for each type of board defined on the ARM Linux site, so consider it "already done" for the D-Link DIR-615 and/or the Marvell RD-88F5181L-VOIP-FE reference board.)
Update (25-Jul-2012): I just received my Dangerous Prototypes Bus Blaster to allow me to use JTAG with either OpenOCD or urjtag, among others. It seems that the resistor and capacitor footprints beside the JTAG header need to be populated to allow JTAG access. Proper SMD resistors and caps are part of my next DigiKey order.