linux-kernel - [PATCH] leds: leds-lp50xx: enable chip before any communication

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Message-ID: <20251016145623.2863553-1-christian@klarinett.li>
Date: Thu, 16 Oct 2025 16:56:23 +0200
From: Christian Hitz <christian@...rinett.li>
To: Lee Jones <lee@...nel.org>,
	Pavel Machek <pavel@...nel.org>,
	Jacek Anaszewski <jacek.anaszewski@...il.com>,
	Dan Murphy <dmurphy@...com>
Cc: Christian Hitz <christian.hitz@....ch>,
	stable@...r.kernel.org,
	Pavel Machek <pavel@....cz>,
	linux-leds@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] leds: leds-lp50xx: enable chip before any communication

From: Christian Hitz <christian.hitz@....ch>

If a GPIO is used to control the chip's enable pin, it needs to be pulled
high before any SPI communication is attempted.
Split lp50xx_enable_disable() into two distinct functions to enforce
correct ordering.
Observe correct timing after manipulating the enable GPIO and SPI
communication.

Fixes: 242b81170fb8 ("leds: lp50xx: Add the LP50XX family of the RGB LED driver")

Signed-off-by: Christian Hitz <christian.hitz@....ch>
Cc: stable@...r.kernel.org
---
 drivers/leds/leds-lp50xx.c | 51 +++++++++++++++++++++++++++-----------
 1 file changed, 36 insertions(+), 15 deletions(-)

diff --git a/drivers/leds/leds-lp50xx.c b/drivers/leds/leds-lp50xx.c
index d19b6a459151..f23e9ae434e4 100644
--- a/drivers/leds/leds-lp50xx.c
+++ b/drivers/leds/leds-lp50xx.c
@@ -52,6 +52,8 @@
 
 #define LP50XX_SW_RESET		0xff
 #define LP50XX_CHIP_EN		BIT(6)
+#define LP50XX_START_TIME_US	500
+#define LP50XX_RESET_TIME_US	3
 
 /* There are 3 LED outputs per bank */
 #define LP50XX_LEDS_PER_MODULE	3
@@ -374,19 +376,42 @@ static int lp50xx_reset(struct lp50xx *priv)
 	return regmap_write(priv->regmap, priv->chip_info->reset_reg, LP50XX_SW_RESET);
 }
 
-static int lp50xx_enable_disable(struct lp50xx *priv, int enable_disable)
+static int lp50xx_enable(struct lp50xx *priv)
 {
 	int ret;
 
-	ret = gpiod_direction_output(priv->enable_gpio, enable_disable);
+	if (priv->enable_gpio) {
+		ret = gpiod_direction_output(priv->enable_gpio, 1);
+		if (ret)
+			return ret;
+
+		udelay(LP50XX_START_TIME_US);
+	} else {
+		ret = lp50xx_reset(priv);
+		if (ret)
+			return ret;
+	}
+
+	return regmap_write(priv->regmap, LP50XX_DEV_CFG0, LP50XX_CHIP_EN);
+}
+
+static int lp50xx_disable(struct lp50xx *priv)
+{
+	int ret;
+
+	ret = regmap_write(priv->regmap, LP50XX_DEV_CFG0, 0);
 	if (ret)
 		return ret;
 
-	if (enable_disable)
-		return regmap_write(priv->regmap, LP50XX_DEV_CFG0, LP50XX_CHIP_EN);
-	else
-		return regmap_write(priv->regmap, LP50XX_DEV_CFG0, 0);
+	if (priv->enable_gpio) {
+		ret = gpiod_direction_output(priv->enable_gpio, 0);
+		if (ret)
+			return ret;
+
+		udelay(LP50XX_RESET_TIME_US);
+	}
 
+	return 0;
 }
 
 static int lp50xx_probe_leds(struct fwnode_handle *child, struct lp50xx *priv,
@@ -453,6 +478,10 @@ static int lp50xx_probe_dt(struct lp50xx *priv)
 		return dev_err_probe(priv->dev, PTR_ERR(priv->enable_gpio),
 				     "Failed to get enable GPIO\n");
 
+	ret = lp50xx_enable(priv);
+	if (ret)
+		return ret;
+
 	priv->regulator = devm_regulator_get(priv->dev, "vled");
 	if (IS_ERR(priv->regulator))
 		priv->regulator = NULL;
@@ -550,14 +579,6 @@ static int lp50xx_probe(struct i2c_client *client)
 		return ret;
 	}
 
-	ret = lp50xx_reset(led);
-	if (ret)
-		return ret;
-
-	ret = lp50xx_enable_disable(led, 1);
-	if (ret)
-		return ret;
-
 	return lp50xx_probe_dt(led);
 }
 
@@ -566,7 +587,7 @@ static void lp50xx_remove(struct i2c_client *client)
 	struct lp50xx *led = i2c_get_clientdata(client);
 	int ret;
 
-	ret = lp50xx_enable_disable(led, 0);
+	ret = lp50xx_disable(led);
 	if (ret)
 		dev_err(led->dev, "Failed to disable chip\n");
 
-- 
2.51.0