The TMIO MMC controller cannot be powered off to save power, when no
card is plugged in, because then it will not be able to detect a new
card-insertion event. On some implementations, however, it is
possible to switch to using another source to detect card insertion.
This patch adds support for such implementations.
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Chris Ball <cjb@laptop.org>