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regulator: Add helpers for low-level register access

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Add helper functions that allow regulator consumers to obtain low-level
details about the regulator hardware, like the voltage selector register
address and such. These details can be useful when configuring hardware
or firmware that want to do low-level access to regulators, with no
involvement from the kernel.

The use-case for Tegra is a voltage-controlled oscillator clocksource
which has control logic to change the supply voltage via I2C to achieve
a desired output clock rate.

Signed-off-by: Tuomas Tynkkynen <ttynkkynen@nvidia.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
This commit is contained in:
Tuomas Tynkkynen
2014-07-21 18:38:48 +03:00
committed by Mark Brown
parent 7171511eae
commit 04eca28cde
3 changed files with 132 additions and 0 deletions
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Documentation/power/regulator/consumer.txt
+35
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@@ -180,3 +180,38 @@ int regulator_unregister_notifier(struct regulator *regulator,
Regulators use the kernel notifier framework to send event to their interested
consumers.
7. Regulator Direct Register Access
===================================
Some kinds of power management hardware or firmware are designed such that
they need to do low-level hardware access to regulators, with no involvement
from the kernel. Examples of such devices are:
- clocksource with a voltage-controlled oscillator and control logic to change
the supply voltage over I2C to achieve a desired output clock rate
- thermal management firmware that can issue an arbitrary I2C transaction to
perform system poweroff during overtemperature conditions
To set up such a device/firmware, various parameters like I2C address of the
regulator, addresses of various regulator registers etc. need to be configured
to it. The regulator framework provides the following helpers for querying
these details.
Bus-specific details, like I2C addresses or transfer rates are handled by the
regmap framework. To get the regulator's regmap (if supported), use :-
struct regmap *regulator_get_regmap(struct regulator *regulator);
To obtain the hardware register offset and bitmask for the regulator's voltage
selector register, use :-
int regulator_get_hardware_vsel_register(struct regulator *regulator,
unsigned *vsel_reg,
unsigned *vsel_mask);
To convert a regulator framework voltage selector code (used by
regulator_list_voltage) to a hardware-specific voltage selector that can be
directly written to the voltage selector register, use :-
int regulator_list_hardware_vsel(struct regulator *regulator,
unsigned selector);