On Tue, Nov 22, 2016 at 11:20 AM, Laxman Dewangan [off-list ref] wrote:

NVIDIA Tegra124 and later SoCs support the multi-voltage level and
low power state of some of its IO pads. The IO pads can work in
the voltage of the 1.8V and 3.3V of IO voltage from IO power rail
sources. When IO interfaces are not used then IO pads can be
configure in low power state to reduce the power consumption from
that IO pads.

On Tegra124, the voltage level of IO power rail source is auto
detected by hardware(SoC) and hence it is only require to configure
in low power mode if IO pads are not used.

On T210 onwards, the auto-detection of voltage level from IO power
rail is removed from SoC and hence SW need to configure the PMC
register explicitly to set proper voltage in IO pads based on
IO rail power source voltage.

This driver adds the IO pad driver to configure the power state and
IO pad voltage based on the usage and power tree via pincontrol
framework. The configuration can be static and dynamic.

Signed-off-by: Laxman Dewangan <ldewangan@nvidia.com>

Overall very nice!

+               rinfo->regulator = devm_regulator_get_optional(dev,
+                                               soc_data->cfg[i].vsupply);

Please just use devm_regulator_get().

As has been discussed at lenth elsewhere "optional" in regulator_get_optional
does *not* mean "software optional", it means "hardware optional".

Such as a terminal that may have a voltage connected or not be
connected to anything at all.

If the system does not define a regulator you will anyway get a
dummy regulator.

Yours,
Linus Walleij