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-rw-r--r--Documentation/devicetree/bindings/pwm/lpc32xx-pwm.txt12
-rw-r--r--Documentation/devicetree/bindings/pwm/mxs-pwm.txt17
-rw-r--r--Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.txt18
-rw-r--r--Documentation/devicetree/bindings/pwm/pwm.txt57
-rw-r--r--Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt28
-rw-r--r--Documentation/pwm.txt76
6 files changed, 208 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/pwm/lpc32xx-pwm.txt b/Documentation/devicetree/bindings/pwm/lpc32xx-pwm.txt
new file mode 100644
index 00000000000..cfe1db3bb6e
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/lpc32xx-pwm.txt
@@ -0,0 +1,12 @@
+LPC32XX PWM controller
+
+Required properties:
+- compatible: should be "nxp,lpc3220-pwm"
+- reg: physical base address and length of the controller's registers
+
+Examples:
+
+pwm@0x4005C000 {
+ compatible = "nxp,lpc3220-pwm";
+ reg = <0x4005C000 0x8>;
+};
diff --git a/Documentation/devicetree/bindings/pwm/mxs-pwm.txt b/Documentation/devicetree/bindings/pwm/mxs-pwm.txt
new file mode 100644
index 00000000000..b16f4a57d11
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/mxs-pwm.txt
@@ -0,0 +1,17 @@
+Freescale MXS PWM controller
+
+Required properties:
+- compatible: should be "fsl,imx23-pwm"
+- reg: physical base address and length of the controller's registers
+- #pwm-cells: should be 2. The first cell specifies the per-chip index
+ of the PWM to use and the second cell is the duty cycle in nanoseconds.
+- fsl,pwm-number: the number of PWM devices
+
+Example:
+
+pwm: pwm@80064000 {
+ compatible = "fsl,imx28-pwm", "fsl,imx23-pwm";
+ reg = <0x80064000 2000>;
+ #pwm-cells = <2>;
+ fsl,pwm-number = <8>;
+};
diff --git a/Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.txt b/Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.txt
new file mode 100644
index 00000000000..bbbeedb4ec0
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/nvidia,tegra20-pwm.txt
@@ -0,0 +1,18 @@
+Tegra SoC PWFM controller
+
+Required properties:
+- compatible: should be one of:
+ - "nvidia,tegra20-pwm"
+ - "nvidia,tegra30-pwm"
+- reg: physical base address and length of the controller's registers
+- #pwm-cells: On Tegra the number of cells used to specify a PWM is 2. The
+ first cell specifies the per-chip index of the PWM to use and the second
+ cell is the duty cycle in nanoseconds.
+
+Example:
+
+ pwm: pwm@7000a000 {
+ compatible = "nvidia,tegra20-pwm";
+ reg = <0x7000a000 0x100>;
+ #pwm-cells = <2>;
+ };
diff --git a/Documentation/devicetree/bindings/pwm/pwm.txt b/Documentation/devicetree/bindings/pwm/pwm.txt
new file mode 100644
index 00000000000..73ec962bfe8
--- /dev/null
+++ b/Documentation/devicetree/bindings/pwm/pwm.txt
@@ -0,0 +1,57 @@
+Specifying PWM information for devices
+======================================
+
+1) PWM user nodes
+-----------------
+
+PWM users should specify a list of PWM devices that they want to use
+with a property containing a 'pwm-list':
+
+ pwm-list ::= <single-pwm> [pwm-list]
+ single-pwm ::= <pwm-phandle> <pwm-specifier>
+ pwm-phandle : phandle to PWM controller node
+ pwm-specifier : array of #pwm-cells specifying the given PWM
+ (controller specific)
+
+PWM properties should be named "pwms". The exact meaning of each pwms
+property must be documented in the device tree binding for each device.
+An optional property "pwm-names" may contain a list of strings to label
+each of the PWM devices listed in the "pwms" property. If no "pwm-names"
+property is given, the name of the user node will be used as fallback.
+
+Drivers for devices that use more than a single PWM device can use the
+"pwm-names" property to map the name of the PWM device requested by the
+pwm_get() call to an index into the list given by the "pwms" property.
+
+The following example could be used to describe a PWM-based backlight
+device:
+
+ pwm: pwm {
+ #pwm-cells = <2>;
+ };
+
+ [...]
+
+ bl: backlight {
+ pwms = <&pwm 0 5000000>;
+ pwm-names = "backlight";
+ };
+
+pwm-specifier typically encodes the chip-relative PWM number and the PWM
+period in nanoseconds. Note that in the example above, specifying the
+"pwm-names" is redundant because the name "backlight" would be used as
+fallback anyway.
+
+2) PWM controller nodes
+-----------------------
+
+PWM controller nodes must specify the number of cells used for the
+specifier using the '#pwm-cells' property.
+
+An example PWM controller might look like this:
+
+ pwm: pwm@7000a000 {
+ compatible = "nvidia,tegra20-pwm";
+ reg = <0x7000a000 0x100>;
+ #pwm-cells = <2>;
+ };
diff --git a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
new file mode 100644
index 00000000000..1e4fc727f3b
--- /dev/null
+++ b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
@@ -0,0 +1,28 @@
+pwm-backlight bindings
+
+Required properties:
+ - compatible: "pwm-backlight"
+ - pwms: OF device-tree PWM specification (see PWM binding[0])
+ - brightness-levels: Array of distinct brightness levels. Typically these
+ are in the range from 0 to 255, but any range starting at 0 will do.
+ The actual brightness level (PWM duty cycle) will be interpolated
+ from these values. 0 means a 0% duty cycle (darkest/off), while the
+ last value in the array represents a 100% duty cycle (brightest).
+ - default-brightness-level: the default brightness level (index into the
+ array defined by the "brightness-levels" property)
+
+Optional properties:
+ - pwm-names: a list of names for the PWM devices specified in the
+ "pwms" property (see PWM binding[0])
+
+[0]: Documentation/devicetree/bindings/pwm/pwm.txt
+
+Example:
+
+ backlight {
+ compatible = "pwm-backlight";
+ pwms = <&pwm 0 5000000>;
+
+ brightness-levels = <0 4 8 16 32 64 128 255>;
+ default-brightness-level = <6>;
+ };
diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt
new file mode 100644
index 00000000000..554290ebab9
--- /dev/null
+++ b/Documentation/pwm.txt
@@ -0,0 +1,76 @@
+Pulse Width Modulation (PWM) interface
+
+This provides an overview about the Linux PWM interface
+
+PWMs are commonly used for controlling LEDs, fans or vibrators in
+cell phones. PWMs with a fixed purpose have no need implementing
+the Linux PWM API (although they could). However, PWMs are often
+found as discrete devices on SoCs which have no fixed purpose. It's
+up to the board designer to connect them to LEDs or fans. To provide
+this kind of flexibility the generic PWM API exists.
+
+Identifying PWMs
+----------------
+
+Users of the legacy PWM API use unique IDs to refer to PWM devices.
+
+Instead of referring to a PWM device via its unique ID, board setup code
+should instead register a static mapping that can be used to match PWM
+consumers to providers, as given in the following example:
+
+ static struct pwm_lookup board_pwm_lookup[] = {
+ PWM_LOOKUP("tegra-pwm", 0, "pwm-backlight", NULL),
+ };
+
+ static void __init board_init(void)
+ {
+ ...
+ pwm_add_table(board_pwm_lookup, ARRAY_SIZE(board_pwm_lookup));
+ ...
+ }
+
+Using PWMs
+----------
+
+Legacy users can request a PWM device using pwm_request() and free it
+after usage with pwm_free().
+
+New users should use the pwm_get() function and pass to it the consumer
+device or a consumer name. pwm_put() is used to free the PWM device.
+
+After being requested a PWM has to be configured using:
+
+int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns);
+
+To start/stop toggling the PWM output use pwm_enable()/pwm_disable().
+
+Implementing a PWM driver
+-------------------------
+
+Currently there are two ways to implement pwm drivers. Traditionally
+there only has been the barebone API meaning that each driver has
+to implement the pwm_*() functions itself. This means that it's impossible
+to have multiple PWM drivers in the system. For this reason it's mandatory
+for new drivers to use the generic PWM framework.
+
+A new PWM controller/chip can be added using pwmchip_add() and removed
+again with pwmchip_remove(). pwmchip_add() takes a filled in struct
+pwm_chip as argument which provides a description of the PWM chip, the
+number of PWM devices provider by the chip and the chip-specific
+implementation of the supported PWM operations to the framework.
+
+Locking
+-------
+
+The PWM core list manipulations are protected by a mutex, so pwm_request()
+and pwm_free() may not be called from an atomic context. Currently the
+PWM core does not enforce any locking to pwm_enable(), pwm_disable() and
+pwm_config(), so the calling context is currently driver specific. This
+is an issue derived from the former barebone API and should be fixed soon.
+
+Helpers
+-------
+
+Currently a PWM can only be configured with period_ns and duty_ns. For several
+use cases freq_hz and duty_percent might be better. Instead of calculating
+this in your driver please consider adding appropriate helpers to the framework.