mmc: sdhci: add quirk for lack of 1.8v support
authorJeetesh Burman <jburman@nvidia.com>
Mon, 16 Dec 2013 12:17:43 +0000 (17:17 +0530)
committerMatthew Pedro <mapedro@nvidia.com>
Wed, 28 May 2014 15:46:23 +0000 (08:46 -0700)
commit61a7d245ef0bd5d299de2219361799a824ecc18d
tree10843d82957d32d9e4141d4fa4eb8405ab979b44
parent8e435e6e4d7155eeffc1fe60ac98b7dab83ed4ec
mmc: sdhci: add quirk for lack of 1.8v support

The OLPC XO-1.75 laptop includes a SDHCI controller which is 1.8v
capable, and it truthfully reports so in its capabilities. This
alternate voltage is used for driving new "UHS-I" SD cards at their
full speed.

However, what the controller doesn't know is that the motherboard
physically doesn't have a 1.8v supply available.

Add a quirk so that systems such as this one can override disable
1.8v support, adding support for UHS-I cards (by running them at
3.3v).

This avoids a problem where the system would first try to run the
card at 1.8v, fail, and then not be able to fully reset the card
to retry at the normal 3.3v voltage.

This is more appropriate than using the MISSING_CAPS quirk, which
is intended for cases where the SDHCI controller is actually lying
about its capabilities, and would force us to somehow override both
caps words from another source.

Bug 1402031

Change-Id: I7ca070a13241e6403eb2e243ebbc441a311110bc
Signed-off-by: Daniel Drake <dsd@laptop.org>
Reviewed-by: Philip Rakity <prakity@nvidia.com>
Signed-off-by: Chris Ball <cjb@laptop.org>
Signed-off-by: Jeetesh Burman <jburman@nvidia.com>
Reviewed-on: http://git-master/r/346323
Reviewed-by: Matthew Pedro <mapedro@nvidia.com>
Tested-by: Matthew Pedro <mapedro@nvidia.com>
drivers/mmc/host/sdhci.c
include/linux/mmc/sdhci.h