Correct way to set coherent_dma_mask on a non-pci device?

[Steve Brown <sbrown@cortland.com>]

There appears to be no function like pci_set_consistent_dma_mask to set 
the coherent mask for a non-pci device.
What is the "proper" way to set it?

The context for the question is a recent change to ssb_dma_set_mask() in 
drivers/ssb/main.c that removed the somewhat fragile, direct 
manipulation of dma_mask and coherent_dma_mask in favor of a call to 
dma_set_mask().
Thanks,
Steve