gpmc_cs_request() causes early boot hang

[Mark Jackson <mpfj-list@mimc.co.uk>]

I'm developing a beaglebone cape board which requires the use of a GPMC 
chip select.

I've chosen GPMC_CS0, and in board-am335xevm.c, I have added the following:-

static void gpmc_test()
{
     unsigned long base = 0x12345678;
     gpmc_cs_request(0, SZ_16M, &base);
     printk(KERN_INFO "gpmc base @ 0x%08lx\n", base);
}

... and added a call to gpmc_test() at the end of am335x_evm_init().

If I try to run this code, the kernel fails to boot, and simply hangs at:-

Uncompressing Linux... done, booting the kernel.

If I comment out the call to gpmc_cs_request(), the system boots as 
expected (but without my required cs).

I've looked at the use of this call in other board files, and can't see 
that their code does anything special so I'm stuck on why this simple 
code fails to work.

Can anyone shed light on what I'm doing wrong ?

Do I have to initialise the gpmc beforehand in some way ?

Cheers
Mark JACKSON