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author | Thierry Reding <thierry.reding@avionic-design.de> | 2011-12-14 11:10:32 +0100 |
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committer | Thierry Reding <thierry.reding@avionic-design.de> | 2012-06-15 12:56:57 +0200 |
commit | 7299ab70e68e20e70cb45fe4ab4b6029fe964acd (patch) | |
tree | b396b29f6170deb3769c0b884ccf0fd64211f6ee /Documentation/devicetree/bindings/pwm | |
parent | e05e5070f0ec2557d2d2ff3655ba03f29e297151 (diff) | |
download | op-kernel-dev-7299ab70e68e20e70cb45fe4ab4b6029fe964acd.zip op-kernel-dev-7299ab70e68e20e70cb45fe4ab4b6029fe964acd.tar.gz |
pwm: Add device tree support
This patch adds helpers to support device tree bindings for the generic
PWM API. Device tree binding documentation for PWM controllers is also
provided.
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Thierry Reding <thierry.reding@avionic-design.de>
Diffstat (limited to 'Documentation/devicetree/bindings/pwm')
-rw-r--r-- | Documentation/devicetree/bindings/pwm/pwm.txt | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/Documentation/devicetree/bindings/pwm/pwm.txt b/Documentation/devicetree/bindings/pwm/pwm.txt new file mode 100644 index 0000000..73ec962 --- /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>; + }; |