[PATCH] leds: pca9532: don't stop blinking for non-zero brightness

[Tobias Deiminger]

pca9532 unexpectedly stopped blinking when changing brightness to a
non-zero value. To reproduce:

 echo timer > /sys/class/leds/led-1/trigger   # blinks
 echo 255 > /sys/class/leds/led-1/brightness  # blinking stops, light on
 cat /sys/class/leds/led-1/trigger            # still claims [timer]

According to Documentation/leds/leds-class.rst, only brightness = 0
shall be a stop condition:

> You can change the brightness value of a LED independently of the
> timer trigger. However, if you set the brightness value to LED_OFF it
> will also disable the timer trigger.

Therefore add a guard to continue blinking when brightness != LED_OFF,
similar to how pca955x does it since 575f10dc64a2 ("leds: pca955x: Add
HW blink support").

Signed-off-by: Tobias Deiminger <tobias.deiminger@xxxxxxxxxxxxx>
---

Notes:
    A more advanced solution was to not simply return early on
    set_brightness, but actually support blinking at arbitrary brightness.
    This would however require conditional fallback to SW blinking, since
    PCA 9532 doesn't support routing PWM 0 (dim) and PWM 1 (blink) in
    series. The bugfix here keeps it simple. Optional SW blinking could be
    tried in a separate patch.

 drivers/leds/leds-pca9532.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/leds/leds-pca9532.c b/drivers/leds/leds-pca9532.c
index 0344189bb991..3de20e087334 100644
--- a/drivers/leds/leds-pca9532.c
+++ b/drivers/leds/leds-pca9532.c
@@ -184,6 +184,8 @@ static int pca9532_set_brightness(struct led_classdev *led_cdev,
 
 	if (value == LED_OFF)
 		led->state = PCA9532_OFF;
+	else if (led->state == PCA9532_PWM1)
+		return 0; /* non-zero brightness shall not stop HW blinking */
 	else if (value == LED_FULL)
 		led->state = PCA9532_ON;
 	else {

base-commit: b2c87f5e98cd88095dbc6802197526703d5e4e48
-- 
2.47.3