[PATCH/RFC v6 03/36] leds: Improve asynchronous path of setting brightness

[Jacek Anaszewski]

led_set_brightness_async function didn't set brightness in an
asynchronous way in all cases. It was mistakenly assuming that all
LED subsystem drivers used work queue in their brightness_set op,
whereas only half of them did that. Modify the function to assure
setting brightness asynchronously in all cases by using existing
set_brightness_work.

Aforementioned modifications change the initial purpose of
set_brightness_work which was used for setting brightness only if blink
timer was active. In order to keep this functionality LED_BLINK_DISABLE
flag is being introduced, as well as a 'new_brightness_value' field is
being added to the struct led_classdev. set_brightness_delayed callback
now needs to use led_set_brightness_sync for setting brightness.
All these improvements entail changes in the led_brightness_set function.

Signed-off-by: Jacek Anaszewski <j.anaszewski@xxxxxxxxxxx>
Cc: Andrew Lunn <andrew@xxxxxxx>
Cc: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
Cc: Pavel Machek <pavel@xxxxxx>
Cc: Stas Sergeev <stsp@xxxxxxxxxxxxxxxxxxxxx>
---
 drivers/leds/led-class.c |   13 ++++++++-----
 drivers/leds/led-core.c  |   20 ++++++++++++++++----
 drivers/leds/leds.h      |    9 +++------
 include/linux/leds.h     |    2 ++
 4 files changed, 29 insertions(+), 15 deletions(-)

diff --git a/drivers/leds/led-class.c b/drivers/leds/led-class.c
index 93a2414..fe11ed8 100644
--- a/drivers/leds/led-class.c
+++ b/drivers/leds/led-class.c
@@ -121,10 +121,10 @@ static void led_timer_function(unsigned long data)
 	brightness = led_get_brightness(led_cdev);
 	if (!brightness) {
 		/* Time to switch the LED on. */
-		if (led_cdev->delayed_set_value) {
+		if (led_cdev->new_brightness_value) {
 			led_cdev->blink_brightness =
-					led_cdev->delayed_set_value;
-			led_cdev->delayed_set_value = 0;
+					led_cdev->new_brightness_value;
+			led_cdev->new_brightness_value = 0;
 		}
 		brightness = led_cdev->blink_brightness;
 		delay = led_cdev->blink_delay_on;
@@ -161,9 +161,12 @@ static void set_brightness_delayed(struct work_struct *ws)
 	struct led_classdev *led_cdev =
 		container_of(ws, struct led_classdev, set_brightness_work);
 
-	led_stop_software_blink(led_cdev);
+	if (led_cdev->flags & LED_BLINK_DISABLE) {
+		led_stop_software_blink(led_cdev);
+		led_cdev->flags &= ~LED_BLINK_DISABLE;
+	}
 
-	led_set_brightness_async(led_cdev, led_cdev->delayed_set_value);
+	led_set_brightness_sync(led_cdev, led_cdev->delayed_set_value);
 }
 
 /**
diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c
index 3f3b71d..b69271f 100644
--- a/drivers/leds/led-core.c
+++ b/drivers/leds/led-core.c
@@ -119,11 +119,23 @@ void led_set_brightness(struct led_classdev *led_cdev,
 {
 	int ret = 0;
 
-	/* delay brightness if soft-blink is active */
+	/*
+	 * In case blinking is on delay brightness setting
+	 * until the next timer tick.
+	 */
 	if (led_cdev->blink_delay_on || led_cdev->blink_delay_off) {
-		led_cdev->delayed_set_value = brightness;
-		if (brightness == LED_OFF)
-			schedule_work(&led_cdev->set_brightness_work);
+		led_cdev->new_brightness_value = brightness;
+
+		/* New brightness will be set on next timer tick. */
+		if (brightness != LED_OFF)
+			return;
+		/*
+		 * If need to disable soft blinking delegate this to the
+		 * work queue task to avoid problems in case we are
+		 * called from hard irq context.
+		 */
+		led_cdev->flags |= LED_BLINK_DISABLE;
+		led_set_brightness_async(led_cdev, brightness);
 		return;
 	}
 
diff --git a/drivers/leds/leds.h b/drivers/leds/leds.h
index 1c026c9..ca38f6a 100644
--- a/drivers/leds/leds.h
+++ b/drivers/leds/leds.h
@@ -17,13 +17,10 @@
 #include <linux/leds.h>
 
 static inline void led_set_brightness_async(struct led_classdev *led_cdev,
-					enum led_brightness value)
+					    enum led_brightness value)
 {
-	value = min(value, led_cdev->max_brightness);
-	led_cdev->brightness = value;
-
-	if (!(led_cdev->flags & LED_SUSPENDED))
-		led_cdev->brightness_set(led_cdev, value);
+	led_cdev->delayed_set_value = value;
+	schedule_work(&led_cdev->set_brightness_work);
 }
 
 static inline int led_get_brightness(struct led_classdev *led_cdev)
diff --git a/include/linux/leds.h b/include/linux/leds.h
index 2377e0f..8fefe72 100644
--- a/include/linux/leds.h
+++ b/include/linux/leds.h
@@ -48,6 +48,7 @@ struct led_classdev {
 #define SET_BRIGHTNESS_ASYNC	(1 << 21)
 #define SET_BRIGHTNESS_SYNC	(1 << 22)
 #define LED_DEV_CAP_FLASH	(1 << 23)
+#define LED_BLINK_DISABLE	(1 << 24)
 
 	/* Set LED brightness level */
 	/* Must not sleep, use a workqueue if needed */
@@ -93,6 +94,7 @@ struct led_classdev {
 
 	struct work_struct	set_brightness_work;
 	int			delayed_set_value;
+	int			new_brightness_value;
 
 #ifdef CONFIG_LEDS_TRIGGERS
 	/* Protects the trigger data below */
-- 
1.7.9.5

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