Some platforms don't support the AB8500 external regulators, so instead
of having a list of is_<platform>() calls prior to calling
ab8500_ext_regulator_init() from ab8500_regulator_probe(), we can only
register as a platform device on platforms which require them. It means
we also have more control over them when booting with Device Tree.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Mark Brown <broonielinaro.org>

Add regulator_get_linear_step(), which returns the voltage step size
between VSEL values for linear regulators.  This is intended for use
by regulator consumers which build their own voltage-to-VSEL tables.

Signed-off-by: Paul Walmsley <pwalmsley@nvidia.com>
Reviewed-by: Andrew Chew <achew@nvidia.com>
Cc: Matthew Longnecker <mlongnecker@nvidia.com>
Signed-off-by: Mark Brown <broonie@linaro.org>

A lot of regulator hardware has ascendant voltage list.
This patch adds regulator_map_voltage_ascend() and export it.

Drivers that have ascendant voltage list can use this as their map_voltage()
operation, this is more efficient than default regulator_map_voltage_iterate()
function.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

ab8500_ext_regulator_exit() never fails.

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Bengt Jonsson <bengt.g.jonsson@stericsson.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>