regulator: Provide optional dummy regulator for consumers

In order to ease transitions with drivers are boards start using regulators
provide an option to cause all regulator_get() calls to succeed, with a
dummy always on regulator being supplied where one has not been configured.
A warning is printed whenever the dummy regulator is used to aid system
development.

This regulator does not implement any regulator operations but will allow
simple consumers which only do enable() and disable() calls to run. It
is kept separate from the fixed voltage regulator to avoid Kconfig
confusion on the part of users when it is extended to allow boards to
explicitly use the dummy regulator to simplify cases where the majority
of supplies are from fixed regulators without software control.

This option is currently only effective for systems which do not specify
full constriants. If required an override could also be provided to allow
these systems to use the dummy regulator, though it is likely that
unconfigured supplies on such systems will lead to error due to
regulators being powered down more aggressively when not in use.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/regulator/Kconfig b/drivers/regulator/Kconfig
index 3c07169498cf..834b48441829 100644
--- a/drivers/regulator/Kconfig
+++ b/drivers/regulator/Kconfig
@@ -27,6 +27,17 @@ config REGULATOR_DEBUG
         help
           Say yes here to enable debugging support.
 
+config REGULATOR_DUMMY
+        bool "Provide a dummy regulator if regulator lookups fail"
+        help
+          If this option is enabled then when a regulator lookup fails
+          and the board has not specified that it has provided full
+          constraints then the regulator core will provide an always
+          enabled dummy regulator will be provided, allowing consumer
+          drivers to continue.
+
+          A warning will be generated when this substitution is done.
+
 config REGULATOR_FIXED_VOLTAGE
         tristate "Fixed voltage regulator support"
         help