linux-kernel - [PATCH] backlight: led_bl: fix initial power state

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Date:   Wed,  5 Jul 2023 15:24:14 +0100
From:   Mans Rullgard <mans@...sr.com>
To:     Lee Jones <lee@...nel.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>
Cc:     Helge Deller <deller@....de>, dri-devel@...ts.freedesktop.org,
        linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] backlight: led_bl: fix initial power state

The condition for the initial power state based on the default
brightness value is reversed.  Fix it.

Furthermore, use the actual state of the LEDs rather than the default
brightness specified in the devicetree as the latter should not cause
the backlight to be automatically turned on.

If the backlight device is not linked to any display, set the initial
power to on unconditionally.

Fixes: ae232e45acf9 ("backlight: add led-backlight driver")
Signed-off-by: Mans Rullgard <mans@...sr.com>
---
Changes in v3:
- Add comment

Changes in v2:
- Use the reported LED state to set initial power state
- Always power on if no phandle in DT
---
 drivers/video/backlight/led_bl.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/video/backlight/led_bl.c b/drivers/video/backlight/led_bl.c
index 3259292fda76..c94843c00a30 100644
--- a/drivers/video/backlight/led_bl.c
+++ b/drivers/video/backlight/led_bl.c
@@ -176,6 +176,7 @@ static int led_bl_probe(struct platform_device *pdev)
 {
 	struct backlight_properties props;
 	struct led_bl_data *priv;
+	int init_brightness;
 	int ret, i;
 
 	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
@@ -190,6 +191,8 @@ static int led_bl_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
+	init_brightness = priv->default_brightness;
+
 	ret = led_bl_parse_levels(&pdev->dev, priv);
 	if (ret < 0) {
 		dev_err(&pdev->dev, "Failed to parse DT data\n");
@@ -200,8 +203,11 @@ static int led_bl_probe(struct platform_device *pdev)
 	props.type = BACKLIGHT_RAW;
 	props.max_brightness = priv->max_brightness;
 	props.brightness = priv->default_brightness;
-	props.power = (priv->default_brightness > 0) ? FB_BLANK_POWERDOWN :
-		      FB_BLANK_UNBLANK;
+
+	/* Set power on if LEDs already on or not linked to a display. */
+	props.power = (init_brightness || !pdev->dev.of_node->phandle) ?
+		FB_BLANK_UNBLANK : FB_BLANK_POWERDOWN;
+
 	priv->bl_dev = backlight_device_register(dev_name(&pdev->dev),
 			&pdev->dev, priv, &led_bl_ops, &props);
 	if (IS_ERR(priv->bl_dev)) {
-- 
2.41.0