Message-ID:  <487777D5.7050807@teltonika.lt>
Date:	Fri, 11 Jul 2008 18:10:13 +0300
From:	Paulius Zaleckas <paulius.zaleckas@...tonika.lt>
To:	linux-kernel@...r.kernel.org
Cc:	linux-arm-kernel@...ts.arm.linux.org.uk
Subject:  Re: [PATCH 10/15] regulator: documentation - consumer interface

Liam Girdwood wrote:
> This adds documentation describing the consumer device interface.
> 
> Signed-off-by: Liam Girdwood <lg@...nsource.wolfsonmicro.com>
> ---
>  Documentation/power/regulator/consumer.txt |  182 ++++++++++++++++++++++++++++
>  1 files changed, 182 insertions(+), 0 deletions(-)
>  create mode 100644 Documentation/power/regulator/consumer.txt
> 
> diff --git a/Documentation/power/regulator/consumer.txt b/Documentation/power/regulator/consumer.txt
> new file mode 100644
> index 0000000..9ea688d
> --- /dev/null
> +++ b/Documentation/power/regulator/consumer.txt
> @@ -0,0 +1,182 @@
> +Regulator Consumer Driver Interface
> +===================================
> +
> +This text describes the regulator interface for consumer device drivers.
> +Please see overview.txt for a description of the terms used in this text.
> +
> +
> +1. Consumer Regulator Access (static & dynamic drivers)
> +=======================================================
> +
> +A consumer driver can get access to it's supply regulator by calling :-
> +
> +regulator = regulator_get(dev, "Vcc");
> +
> +The consumer passes in it's struct device pointer and power supply ID. The core
> +then finds the correct regulator by consulting a machine specific lookup table.
> +If the lookup is successful then this call will return a pointer to the struct
> +regulator that supplies this consumer.
> +
> +To release the regulator the consumer driver should call :-
> +
> +regulator_put(regulator);
> +
> +Consumers can be supplied by more than one regulator e.g. codec consumer with
> +analog and digital supplies :-
> +
> +digital = regulator_get(dev, "Vcc");  /* digital core */
> +analog = regulator_get(dev, "Avdd");  /* analog */
> +
> +The regulator access functions regulator_get() and regulator_put() will
> +usually be called in your device drivers probe() and remove() respectively.
> +
> +
> +2. Regulator Output Enable & Disable (static & dynamic drivers)
> +====================================================================
> +
> +A consumer can enable it's power supply by calling:-
> +
> +int regulator_enable(regulator);
> +
> +NOTE: The supply may already be enabled before regulator_enabled() is called.
> +This may happen if the consumer shares the regulator or the regulator has been
> +previously enabled by bootloader or kernel board initialisation code.

initialization
         ^
> +
> +A consumer can determine if a regulator is enabled by calling :-
> +
> +int regulator_is_enabled(regulator);
> +
> +This will return > zero when the regulator is enabled.
> +
> +
> +A consumer can disable it's supply when no longer needed by calling :-
> +
> +int regulator_disable(regulator);
> +
> +NOTE: This may not disable the supply if it's shared with other consumers. The
> +regulator will only be disabled when the enabled reference count is zero.
> +
> +Finally, a regulator can be forcefully disabled in the case of an emergency :-
> +
> +int regulator_force_disable(regulator);
> +
> +NOTE: this will immediately and forcefully shutdown the regulator output. All
> +consumers will be powered off.
> +
> +
> +3. Regulator Voltage Control & Status (dynamic drivers)
> +======================================================
> +
> +Some consumer drivers need to be able to dynamically change their supply
> +voltage to match system operating points. e.g. CPUfreq drivers can scale
> +voltage along with frequency to save power, SD drivers may need to select the
> +correct card voltage, etc.
> +
> +Consumers can control their supply voltage by calling :-
> +
> +int regulator_set_voltage(regulator, min_uV, max_uV);
> +
> +Where min_uV and max_uV are the minimum and maximum acceptable voltages in
> +microvolts.
> +
> +NOTE: this can be called when the regulator is enabled or disabled. If called
> +when enabled, then the voltage changes instantly, otherwise the voltage
> +configuration changes and the voltage is physically set when the regulator is
> +next enabled.
> +
> +The regulators configured voltage output can be found by calling :-
> +
> +int regulator_get_voltage(regulator);
> +
> +NOTE: get_voltage() will return the configured output voltage whether the
> +regulator is enabled or disabled and should NOT be used to determine regulator
> +output state. However this can be used in conjunction with is_enabled() to
> +determind the regulator physical output voltage.

determine
         ^
> +
> +
> +4. Regulator Current Limit Control & Status (dynamic drivers)
> +===========================================================
> +
> +Some consumer drivers need to be able to dynamically change their supply
> +current limit to match system operating points. e.g. LCD backlight driver can
> +change the current limit to vary the backlight brightness, USB drivers may want
> +to set the limit to 500mA when supplying power.
> +
> +Consumers can control their supply current limit by calling :-
> +
> +int regulator_set_current_limit(regulator, min_uV, max_uV);
> +
> +Where min_uA and max_uA are the minimum and maximum acceptable current limit in
> +microamps.
> +
> +NOTE: this can be called when the regulator is enabled or disabled. If called
> +when enabled, then the current limit changes instantly, otherwise the current
> +limit configuration changes and the current limit is physically set when the
> +regulator is next enabled.
> +
> +A regulators current limit can be found by calling :-
> +
> +int regulator_get_current_limit(regulator);
> +
> +NOTE: get_current_limit() will return the current limit whether the regulator
> +is enabled or disabled and should not be used to determine regulator current
> +load.
> +
> +
> +5. Regulator Operating Mode Control & Status (dynamic drivers)
> +=============================================================
> +
> +Some consumers can further save system power by changing the operating mode of
> +their supply regulator to be more efficient when the consumers operating state
> +changes. e.g. consumer driver is idle and subsequently draws less current
> +
> +Regulator operating mode can be changed indirectly or directly.
> +
> +Indirect operating mode control.
> +--------------------------------
> +Consumer drivers can request a change in their supply regulator operating mode
> +by calling :-
> +
> +int regulator_set_optimum_mode(struct regulator *regulator, int load_uA);
> +
> +This will cause the core to recalculate the total load on the regulator (based
> +on all it's consumers) and change operating mode (if necessary and permitted)
> +to best match the current operating load.
> +
> +The load_uA value can be determined from the consumers datasheet. e.g.most
> +datasheets have tables showing the max current consumed in certain situations.
> +
> +Most consumers will use indirect operating mode control since they have no
> +knowledge of the regulator or whether the regulator is shared with other
> +consumers.
> +
> +Direct operating mode control.
> +------------------------------
> +Bespoke or tightly coupled drivers may want to directly control regulator
> +operating mode depending on their operating point. This can be achieved by
> +calling :-
> +
> +int regulator_set_mode(struct regulator *regulator, unsigned int mode);
> +unsigned int regulator_get_mode(struct regulator *regulator);
> +
> +Direct mode will only be used by consumers that *know* about the regulator and
> +are not sharing the regulator with other consumers.
> +
> +
> +6. Regulator Events
> +===================
> +Regulators can notify consumers of external events. Events could be received by
> +consumers under regulator stress or failure conditions.
> +
> +Consumers can register interest in regulator events by calling :-
> +
> +int regulator_register_notifier(struct regulator *regulator,
> +			      struct notifier_block *nb);
> +
> +Consumers can uregister interest by calling :-
> +
> +int regulator_unregister_notifier(struct regulator *regulator,
> +				struct notifier_block *nb);
> +
> +Regulators use the kernel notifier framework to send event to thier interested
> +consumers.

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