0001 Specifying PWM information for devices
0002 ======================================
0003
0004 1) PWM user nodes
0005 -----------------
0006
0007 PWM users should specify a list of PWM devices that they want to use
0008 with a property containing a 'pwm-list':
0009
0010 pwm-list ::= <single-pwm> [pwm-list]
0011 single-pwm ::= <pwm-phandle> <pwm-specifier>
0012 pwm-phandle : phandle to PWM controller node
0013 pwm-specifier : array of #pwm-cells specifying the given PWM
0014 (controller specific)
0015
0016 PWM properties should be named "pwms". The exact meaning of each pwms
0017 property must be documented in the device tree binding for each device.
0018 An optional property "pwm-names" may contain a list of strings to label
0019 each of the PWM devices listed in the "pwms" property. If no "pwm-names"
0020 property is given, the name of the user node will be used as fallback.
0021
0022 Drivers for devices that use more than a single PWM device can use the
0023 "pwm-names" property to map the name of the PWM device requested by the
0024 pwm_get() call to an index into the list given by the "pwms" property.
0025
0026 The following example could be used to describe a PWM-based backlight
0027 device:
0028
0029 pwm: pwm {
0030 #pwm-cells = <2>;
0031 };
0032
0033 [...]
0034
0035 bl: backlight {
0036 pwms = <&pwm 0 5000000>;
0037 pwm-names = "backlight";
0038 };
0039
0040 Note that in the example above, specifying the "pwm-names" is redundant
0041 because the name "backlight" would be used as fallback anyway.
0042
0043 pwm-specifier typically encodes the chip-relative PWM number and the PWM
0044 period in nanoseconds.
0045
0046 Optionally, the pwm-specifier can encode a number of flags (defined in
0047 <dt-bindings/pwm/pwm.h>) in a third cell:
0048 - PWM_POLARITY_INVERTED: invert the PWM signal polarity
0049
0050 Example with optional PWM specifier for inverse polarity
0051
0052 bl: backlight {
0053 pwms = <&pwm 0 5000000 PWM_POLARITY_INVERTED>;
0054 pwm-names = "backlight";
0055 };
0056
0057 2) PWM controller nodes
0058 -----------------------
0059
0060 See pwm.yaml.
