forked from Minki/linux
58fd822b2e
Document the pwm-dutycycle-unit and pwm-dutycycle-range properties. Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com> Acked-by: Brian Norris <briannorris@chromium.org> Acked-by: Rob Herring <robh@kernel.org> Acked-by: Mark Brown <broonie@kernel.org> Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
93 lines
3.1 KiB
Plaintext
93 lines
3.1 KiB
Plaintext
Bindings for the Generic PWM Regulator
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======================================
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Currently supports 2 modes of operation:
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Voltage Table: When in this mode, a voltage table (See below) of
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predefined voltage <=> duty-cycle values must be
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provided via DT. Limitations are that the regulator can
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only operate at the voltages supplied in the table.
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Intermediary duty-cycle values which would normally
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allow finer grained voltage selection are ignored and
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rendered useless. Although more control is given to
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the user if the assumptions made in continuous-voltage
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mode do not reign true.
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Continuous Voltage: This mode uses the regulator's maximum and minimum
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supplied voltages specified in the
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regulator-{min,max}-microvolt properties to calculate
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appropriate duty-cycle values. This allows for a much
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more fine grained solution when compared with
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voltage-table mode above. This solution does make an
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assumption that a %50 duty-cycle value will cause the
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regulator voltage to run at half way between the
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supplied max_uV and min_uV values.
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Required properties:
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--------------------
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- compatible: Should be "pwm-regulator"
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- pwms: PWM specification (See: ../pwm/pwm.txt)
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Only required for Voltage Table Mode:
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- voltage-table: Voltage and Duty-Cycle table consisting of 2 cells
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First cell is voltage in microvolts (uV)
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Second cell is duty-cycle in percent (%)
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Optional properties for Continuous mode:
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- pwm-dutycycle-unit: Integer value encoding the duty cycle unit. If not
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defined, <100> is assumed, meaning that
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pwm-dutycycle-range contains values expressed in
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percent.
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- pwm-dutycycle-range: Should contain 2 entries. The first entry is encoding
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the dutycycle for regulator-min-microvolt and the
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second one the dutycycle for regulator-max-microvolt.
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Duty cycle values are expressed in pwm-dutycycle-unit.
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If not defined, <0 100> is assumed.
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NB: To be clear, if voltage-table is provided, then the device will be used
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in Voltage Table Mode. If no voltage-table is provided, then the device will
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be used in Continuous Voltage Mode.
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Optional properties:
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--------------------
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- enable-gpios: GPIO to use to enable/disable the regulator
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Any property defined as part of the core regulator binding can also be used.
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(See: ../regulator/regulator.txt)
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Continuous Voltage With Enable GPIO Example:
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pwm_regulator {
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compatible = "pwm-regulator;
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pwms = <&pwm1 0 8448 0>;
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enable-gpios = <&gpio0 23 GPIO_ACTIVE_HIGH>;
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regulator-min-microvolt = <1016000>;
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regulator-max-microvolt = <1114000>;
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regulator-name = "vdd_logic";
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/* unit == per-mille */
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pwm-dutycycle-unit = <1000>;
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/*
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* Inverted PWM logic, and the duty cycle range is limited
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* to 30%-70%.
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*/
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pwm-dutycycle-range <700 300>; /* */
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};
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Voltage Table Example:
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pwm_regulator {
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compatible = "pwm-regulator;
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pwms = <&pwm1 0 8448 0>;
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regulator-min-microvolt = <1016000>;
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regulator-max-microvolt = <1114000>;
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regulator-name = "vdd_logic";
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/* Voltage Duty-Cycle */
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voltage-table = <1114000 0>,
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<1095000 10>,
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<1076000 20>,
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<1056000 30>,
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<1036000 40>,
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<1016000 50>;
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};
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