Dear Lee,

On Tue, 08 Nov 2016, Lukasz Majewski wrote:

quoted

Dear All,

quoted

The commit a55944ca82d2 ("backlight: update bd state & fb_blank
properties when necessary") has posed some extra restrictions on
blanking and unblanking frame buffer device.

Unfortunately, pwm_bl driver's probe did not initialize members of
struct backlight_device necessary for further blank/unblank
operation.

This code in case of initial unblank of backlight device (default 
behaviour) sets use_count to 1 and marks this particular backlight
device as used by all available fb devices (since it is not known
during probe how much and which fb devices will be assigned).

Without this code, the backlight works properly until one tries to
blank it manually from sysfs with "echo 1

quoted

/sys/class/graphics/fb0/blank". Since fb_bl_on[0] and use_count
were both set to 0, the logic at

fb_notifier_callback (@backlight.c) thought that we didn't turn on
(unblanked) the backlight device and refuses to disable (blank)
it. As a result we see garbage from fb displayed.

COmments/acks are more than welcome :-)

Ah, it looks like you dropped Jingoo from the list!

I can only apologize for such situation.... strange mistake.

I'll reply to the original mail with him in CC.

Thank you for your help.

Best regards,
Lukasz Majewski

quoted

quoted

Signed-off-by: Lukasz Majewski <redacted>
---
The patch has been tested on i.MX6q with 4.9-rc3
SHA1: a909d3e636995ba7c349e2ca5dbb528154d4ac30
---
Changes for v2:
- Update commit message with proper other commit reference

---
 drivers/video/backlight/pwm_bl.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/video/backlight/pwm_bl.c

b/drivers/video/backlight/pwm_bl.c index 1261400..6859ba0 100644

--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c

@@ -202,7 +202,7 @@ static int pwm_backlight_probe(struct

platform_device *pdev) struct pwm_bl_data *pb;
 	int initial_blank = FB_BLANK_UNBLANK;
 	struct pwm_args pargs;
-	int ret;
+	int ret, i;
 
 	if (!data) {
 		ret = pwm_backlight_parse_dt(&pdev->dev,
&defdata); @@ -348,6 +348,14 @@ static int
pwm_backlight_probe(struct platform_device *pdev) 
 	bl->props.brightness = data->dft_brightness;
 	bl->props.power = initial_blank;
+
+	if (initial_blank == FB_BLANK_UNBLANK) {
+		for (i = 0; i < FB_MAX; i++)
+			bl->fb_bl_on[i] = true;
+
+		bl->use_count = 1;
+	}
+
 	backlight_update_status(bl);
 
 	platform_set_drvdata(pdev, bl);