path: root/Documentation/power
diff options
authorTuomas Tynkkynen <ttynkkynen@nvidia.com>2014-07-21 18:38:48 +0300
committerMark Brown <broonie@linaro.org>2014-07-25 18:43:48 +0100
commit04eca28cde52cdf9eb91e127cc358ad79a8ec53b (patch)
treecb4507f5e7f2430325312c86332fbe3ce887879b /Documentation/power
parent7171511eaec5bf23fb06078f59784a3a0626b38f (diff)
regulator: Add helpers for low-level register access
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>
Diffstat (limited to 'Documentation/power')
1 files changed, 35 insertions, 0 deletions
diff --git a/Documentation/power/regulator/consumer.txt b/Documentation/power/regulator/consumer.txt
index 55c4175d8099..81c0e2b49cd8 100644
--- a/Documentation/power/regulator/consumer.txt
+++ b/Documentation/power/regulator/consumer.txt
@@ -180,3 +180,38 @@ int regulator_unregister_notifier(struct regulator *regulator,
Regulators use the kernel notifier framework to send event to their interested
+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);

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