commit 753251d0fe2c7ac91d0c9f68a60540d892cd6564
author Dario Binacchi <dariobin@libero.it> Sun Oct 11 14:28:04 2020 +0200
committer Anatolij Gustschin <agust@denx.de> Sun Oct 18 15:07:33 2020 +0200
tree 3baaf2748b10f35d80c1ee06477e63f1fba5d778
parent 4d570875ded116e9c856e421fd3dc492d9c992c1

video: backlight: fix pwm's duty cycle calculation

For levels equal to the maximum value, the duty cycle must be equal to
the period.

Signed-off-by: Dario Binacchi <dariobin@libero.it>
Reviewed-by: Simon Glass <sjg@chromium.org>

drivers/video/pwm_backlight.c

diff --git a/drivers/video/pwm_backlight.c b/drivers/video/pwm_backlight.c
index acfde7b..9519180 100644
--- a/drivers/video/pwm_backlight.c
+++ b/drivers/video/pwm_backlight.c
@@ -63,7 +63,7 @@
 	int ret;
 
 	duty_cycle = priv->period_ns * (priv->cur_level - priv->min_level) /
-		(priv->max_level - priv->min_level + 1);
+		(priv->max_level - priv->min_level);
 	ret = pwm_set_config(priv->pwm, priv->channel, priv->period_ns,
 			     duty_cycle);
 	if (ret)

test/dm/panel.c

diff --git a/test/dm/panel.c b/test/dm/panel.c
index a840fb4..49f5ac7 100644
--- a/test/dm/panel.c
+++ b/test/dm/panel.c
@@ -40,7 +40,7 @@
 	ut_assertok(sandbox_pwm_get_config(pwm, 0, &period_ns, &duty_ns,
 					   &enable, &polarity));
 	ut_asserteq(1000, period_ns);
-	ut_asserteq(170 * 1000 / 256, duty_ns);
+	ut_asserteq(170 * 1000 / 255, duty_ns);
 	ut_asserteq(true, enable);
 	ut_asserteq(false, polarity);
 	ut_asserteq(1, sandbox_gpio_get_value(gpio, 1));
@@ -49,29 +49,29 @@
 	ut_assertok(panel_set_backlight(dev, 40));
 	ut_assertok(sandbox_pwm_get_config(pwm, 0, &period_ns, &duty_ns,
 					   &enable, &polarity));
-	ut_asserteq(64 * 1000 / 256, duty_ns);
+	ut_asserteq(64 * 1000 / 255, duty_ns);
 
 	ut_assertok(panel_set_backlight(dev, BACKLIGHT_MAX));
 	ut_assertok(sandbox_pwm_get_config(pwm, 0, &period_ns, &duty_ns,
 					   &enable, &polarity));
-	ut_asserteq(255 * 1000 / 256, duty_ns);
+	ut_asserteq(255 * 1000 / 255, duty_ns);
 
 	ut_assertok(panel_set_backlight(dev, BACKLIGHT_MIN));
 	ut_assertok(sandbox_pwm_get_config(pwm, 0, &period_ns, &duty_ns,
 					   &enable, &polarity));
-	ut_asserteq(0 * 1000 / 256, duty_ns);
+	ut_asserteq(0 * 1000 / 255, duty_ns);
 	ut_asserteq(1, sandbox_gpio_get_value(gpio, 1));
 
 	ut_assertok(panel_set_backlight(dev, BACKLIGHT_DEFAULT));
 	ut_assertok(sandbox_pwm_get_config(pwm, 0, &period_ns, &duty_ns,
 					   &enable, &polarity));
 	ut_asserteq(true, enable);
-	ut_asserteq(170 * 1000 / 256, duty_ns);
+	ut_asserteq(170 * 1000 / 255, duty_ns);
 
 	ut_assertok(panel_set_backlight(dev, BACKLIGHT_OFF));
 	ut_assertok(sandbox_pwm_get_config(pwm, 0, &period_ns, &duty_ns,
 					   &enable, &polarity));
-	ut_asserteq(0 * 1000 / 256, duty_ns);
+	ut_asserteq(0 * 1000 / 255, duty_ns);
 	ut_asserteq(0, sandbox_gpio_get_value(gpio, 1));
 	ut_asserteq(false, regulator_get_enable(reg));