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authorJames Morris <james.l.morris@oracle.com>2012-08-17 20:42:30 +1000
committerJames Morris <james.l.morris@oracle.com>2012-08-17 20:42:30 +1000
commit51b743fe87d7fb3dba7a2ff4a1fe23bb65dc2245 (patch)
treef8b8f601713a3ecb264eb9f145636343d9350520 /Documentation/devicetree/bindings/pwm/pwm.txt
parent9f99798ff49e73dded73a8c674044ea6fb6af651 (diff)
parentd9875690d9b89a866022ff49e3fcea892345ad92 (diff)
downloadlinux-51b743fe87d7fb3dba7a2ff4a1fe23bb65dc2245.tar.gz
Merge tag 'v3.6-rc2' into next
Linux 3.6-rc2 Resync with Linus.
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+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>;
+ };