OsmocomBB

	 * The exact wiring of ALL Calypso GPIO and multifunction pins

	 * inside the GTM900-B module is currently unknown, and will

	 * remain so until and unless someone goes through the effort

	 * of slicing a sacrificial module, imaging all inner and outer

	 * copper layers of its PCB, and tracing out the signal connections

	 * of interest.  Therefore, it is not clear exactly what we

	 * should do with all those GPIO and multifunction pins that are

	 * unused from the functional standpoint.  The following code

	 * was copied by steve-m from the gta0x port; on the gta0x target

	 * we *know* (thanks to published PCB design files) that these pins

	 * are physically unconnected and thus should be configured as

	 * dummy outputs in order to avoid floating inputs, but such knowledge

	 * is currently lacking for the GTM900-B target.

	 *

	 * We do know, however, that GPIO3 should be configured as an input

	 * and not an output: Huawei designated this GPIO to serve as the DTR

	 * input to the modem (it is defined as such in Huawei's official

	 * module interface pinout docs), there is a pull-down resistor to GND

	 * inside the module on this GPIO3 pin, so it won't float if left

	 * unconnected, and configuring it as a Calypso output would be

	 * dangerous: if an external CP2105 or FT2232x or RS-232 receiver

	 * chip drives its DTR output into this line, and Calypso also drives

	 * it as an output, the two outputs will fight, potentially damaging

	 * one of the chips.

	writew(0xC008, IO_CNTL_REG);