linux-kernel - [PATCH] leds: expresswire: Fix chip state breakage

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Message-Id: <20250829-expresswire-fix-v1-1-f8c8c6ad6c5f@dujemihanovic.xyz>
Date: Fri, 29 Aug 2025 23:08:30 +0200
From: Duje Mihanović <duje@...emihanovic.xyz>
To: Lee Jones <lee@...nel.org>, Pavel Machek <pavel@...nel.org>
Cc: Karel Balej <balejk@...fyz.cz>, David Wronek <david@...nlining.org>, 
 phone-devel@...r.kernel.org, ~postmarketos/upstreaming@...ts.sr.ht, 
 linux-leds@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Duje Mihanović <duje@...emihanovic.xyz>
Subject: [PATCH] leds: expresswire: Fix chip state breakage

It is possible to put the hardware state of the KTD2801 chip in an
unknown state by rapidly changing the brightness for a short period of
time (for example, with a brightness slider). When this happens, the
brightness is stuck on max and cannot be changed until the chip is power
cycled.

Fix this by disabling interrupts while the chip is being programmed.
While at it, make expresswire_power_off() use fsleep() and also unexport
some functions meant to be internal.

Signed-off-by: Duje Mihanović <duje@...emihanovic.xyz>
---
 drivers/leds/leds-expresswire.c  | 24 +++++++++++++++++-------
 include/linux/leds-expresswire.h |  3 ---
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/drivers/leds/leds-expresswire.c b/drivers/leds/leds-expresswire.c
index bb69be228a6d3c7a8f2abc7fa75bd473d4c7c79c..25c6b159a6ee93210bf8239388b5cdc434872240 100644
--- a/drivers/leds/leds-expresswire.c
+++ b/drivers/leds/leds-expresswire.c
@@ -9,6 +9,7 @@
 #include <linux/delay.h>
 #include <linux/export.h>
 #include <linux/gpio/consumer.h>
+#include <linux/irqflags.h>
 #include <linux/types.h>
 
 #include <linux/leds-expresswire.h>
@@ -16,37 +17,41 @@
 void expresswire_power_off(struct expresswire_common_props *props)
 {
 	gpiod_set_value_cansleep(props->ctrl_gpio, 0);
-	usleep_range(props->timing.poweroff_us, props->timing.poweroff_us * 2);
+	fsleep(props->timing.poweroff_us);
 }
 EXPORT_SYMBOL_NS_GPL(expresswire_power_off, "EXPRESSWIRE");
 
 void expresswire_enable(struct expresswire_common_props *props)
 {
+	unsigned long flags;
+
+	local_irq_save(flags);
+
 	gpiod_set_value(props->ctrl_gpio, 1);
 	udelay(props->timing.detect_delay_us);
 	gpiod_set_value(props->ctrl_gpio, 0);
 	udelay(props->timing.detect_us);
 	gpiod_set_value(props->ctrl_gpio, 1);
+
+	local_irq_restore(flags);
 }
 EXPORT_SYMBOL_NS_GPL(expresswire_enable, "EXPRESSWIRE");
 
-void expresswire_start(struct expresswire_common_props *props)
+static void expresswire_start(struct expresswire_common_props *props)
 {
 	gpiod_set_value(props->ctrl_gpio, 1);
 	udelay(props->timing.data_start_us);
 }
-EXPORT_SYMBOL_NS_GPL(expresswire_start, "EXPRESSWIRE");
 
-void expresswire_end(struct expresswire_common_props *props)
+static void expresswire_end(struct expresswire_common_props *props)
 {
 	gpiod_set_value(props->ctrl_gpio, 0);
 	udelay(props->timing.end_of_data_low_us);
 	gpiod_set_value(props->ctrl_gpio, 1);
 	udelay(props->timing.end_of_data_high_us);
 }
-EXPORT_SYMBOL_NS_GPL(expresswire_end, "EXPRESSWIRE");
 
-void expresswire_set_bit(struct expresswire_common_props *props, bool bit)
+static void expresswire_set_bit(struct expresswire_common_props *props, bool bit)
 {
 	if (bit) {
 		gpiod_set_value(props->ctrl_gpio, 0);
@@ -60,13 +65,18 @@ void expresswire_set_bit(struct expresswire_common_props *props, bool bit)
 		udelay(props->timing.short_bitset_us);
 	}
 }
-EXPORT_SYMBOL_NS_GPL(expresswire_set_bit, "EXPRESSWIRE");
 
 void expresswire_write_u8(struct expresswire_common_props *props, u8 val)
 {
+	unsigned long flags;
+
+	local_irq_save(flags);
+
 	expresswire_start(props);
 	for (int i = 7; i >= 0; i--)
 		expresswire_set_bit(props, val & BIT(i));
 	expresswire_end(props);
+
+	local_irq_restore(flags);
 }
 EXPORT_SYMBOL_NS_GPL(expresswire_write_u8, "EXPRESSWIRE");
diff --git a/include/linux/leds-expresswire.h b/include/linux/leds-expresswire.h
index a422921f4159f2f51e40f50ad5c9d89d9070511a..7f8c4795f69fa0337bd3b201279652c8e353c6d4 100644
--- a/include/linux/leds-expresswire.h
+++ b/include/linux/leds-expresswire.h
@@ -30,9 +30,6 @@ struct expresswire_common_props {
 
 void expresswire_power_off(struct expresswire_common_props *props);
 void expresswire_enable(struct expresswire_common_props *props);
-void expresswire_start(struct expresswire_common_props *props);
-void expresswire_end(struct expresswire_common_props *props);
-void expresswire_set_bit(struct expresswire_common_props *props, bool bit);
 void expresswire_write_u8(struct expresswire_common_props *props, u8 val);
 
 #endif /* _LEDS_EXPRESSWIRE_H */

---
base-commit: 1b237f190eb3d36f52dffe07a40b5eb210280e00
change-id: 20250829-expresswire-fix-663d1b3c32aa

Best regards,
-- 
Duje Mihanović <duje@...emihanovic.xyz>