[PATCH] backlight: ktd253: Stabilize backlight

[Linus Walleij]

Remove interrupt disablement during backlight setting. It is
way to dangerous and makes platforms instable by having it
miss vblank IRQs leading to the graphics derailing.

The code is using ndelay() which is not available on
platforms such as ARM and will result in 32 * udelay(1)
which is substantial.

Fixes: 5317f37e48b9 ("backlight: Add Kinetic KTD253 backlight driver")
Cc: Stephan Gerhold <stephan at gerhold.net>
Reported-by: newbyte at disroot.org
Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
---
 drivers/video/backlight/ktd253-backlight.c | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/drivers/video/backlight/ktd253-backlight.c b/drivers/video/backlight/ktd253-backlight.c
index a7df5bcca9da..b79a47c2801f 100644
--- a/drivers/video/backlight/ktd253-backlight.c
+++ b/drivers/video/backlight/ktd253-backlight.c
@@ -40,7 +40,6 @@ static int ktd253_backlight_update_status(struct backlight_device *bl)
 	int brightness = backlight_get_brightness(bl);
 	u16 target_ratio;
 	u16 current_ratio = ktd253->ratio;
-	unsigned long flags;
 
 	dev_dbg(ktd253->dev, "new brightness/ratio: %d/32\n", brightness);
 
@@ -69,13 +68,9 @@ static int ktd253_backlight_update_status(struct backlight_device *bl)
 	}
 
 	/*
-	 * WARNING:
-	 * The loop to set the correct current level is performed
-	 * with interrupts disabled as it is timing critical.
 	 * The maximum number of cycles of the loop is 32
 	 * so the time taken will be (T_LOW_NS + T_HIGH_NS + loop_time) * 32,
 	 */
-	local_irq_save(flags);
 	while (current_ratio != target_ratio) {
 		/*
 		 * These GPIO operations absolutely can NOT sleep so no
@@ -92,7 +87,6 @@ static int ktd253_backlight_update_status(struct backlight_device *bl)
 		else
 			current_ratio--;
 	}
-	local_irq_restore(flags);
 	ktd253->ratio = current_ratio;
 
 	dev_dbg(ktd253->dev, "new ratio set to %d/32\n", target_ratio);
-- 
2.31.1