Continuing the work on coupled regulators

Hello,

Maciej moved on to work on something else and kindly allowed me to take over the coupled regulators patches [0] which I'll try to finalize.

I recently started to work on adding DVFS support to the CPUFreq driver of NVIDIA Tegra20/30 which require the coupled regulators functionality. Both Tegra20 and Tegra30 have the voltage "max-spread" constraint. Tegra30 has an additional constraint, the "max-step" voltage.

What is done in this series:

1. Re-worked the original "Add voltage balancing mechanism" patch from Maciej by:
1) Fixing infinite loop within regulator_balance_voltage().
2) Handling suspend_state_t properly.
3) Fixing broken compilation of the patch.

2. Added pair of patches to clean up regulator-couple resolving.

3. Changed device tree binding of the regulator-coupled-max-spread property to make it more flexible.

4. Added new device tree property, the regulator-max-step-microvolt.

5. Implemented wait/wound mutex which was suggested by Lucas Stach in the review comment to [0]. I've tested w/w locking extensively (including CONFIG_DEBUG_WW_MUTEX_SLOWPATH) and quite confident that everything is okay.

6. Patches were tested with KASAN on Tegra20 / Tegra30, I tried to cover various cases and verified that voltage constraints not violated under different circumstances.

Please review, thanks.

[0] https://lkml.org/lkml/2018/4/23/619

Dmitry Osipenko (9):
regulator: core: Mutually resolve regulators coupling
regulator: core: Don't allow to get regulator until all couples
resolved
dt-bindings: regulator: Change regulator-coupled-max-spread property
regulator: core: Limit regulators coupling to a single couple
dt-bindings: regulator: Document new regulator-max-step-microvolt
property
regulator: core: Add new max_uV_step constraint
regulator: core: Decouple regulators on regulator_unregister()
regulator: core: Use ww_mutex for regulators locking
regulator: core: Properly handle case where supply is the couple

Maciej Purski (2):
regulator: core: Add voltage balancing mechanism
regulator: core: Change voltage setting path

 .../bindings/regulator/regulator.txt          |   7 +-
 drivers/regulator/core.c                      | 821 +++++++++++++++---
 drivers/regulator/of_regulator.c              |   4 +
 include/linux/regulator/driver.h              |   5 +-
 include/linux/regulator/machine.h             |   3 +
 5 files changed, 713 insertions(+), 127 deletions(-)

2.19.0