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-rw-r--r--Documentation/pwm.txt10
1 files changed, 9 insertions, 1 deletions
diff --git a/Documentation/pwm.txt b/Documentation/pwm.txt
index 93cb97974986..ca895fd211e4 100644
--- a/Documentation/pwm.txt
+++ b/Documentation/pwm.txt
@@ -19,7 +19,8 @@ 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),
+ PWM_LOOKUP("tegra-pwm", 0, "pwm-backlight", NULL,
+ 50000, PWM_POLARITY_NORMAL),
};
static void __init board_init(void)
@@ -97,6 +98,13 @@ pwm_chip as argument which provides a description of the PWM chip, the
number of PWM devices provided by the chip and the chip-specific
implementation of the supported PWM operations to the framework.
+When implementing polarity support in a PWM driver, make sure to respect the
+signal conventions in the PWM framework. By definition, normal polarity
+characterizes a signal starts high for the duration of the duty cycle and
+goes low for the remainder of the period. Conversely, a signal with inversed
+polarity starts low for the duration of the duty cycle and goes high for the
+remainder of the period.
+
Locking
-------