X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=Documentation%2Fpwm.txt;h=ca895fd211e4e9f5f6bd0fc6a13bf60d9a0c14b2;hb=16d52ef7c026f925893a1c0fc46516349928f319;hp=93cb979749860f323bb797ce2adc2923d629e1ed;hpb=62a3a12667ac551c0251d6437372c34a98dd991c;p=firefly-linux-kernel-4.4.55.git

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
 -------