linux-kernel - [PATCH v2] leds: expresswire: Fix chip state breakage

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Message-Id: <20251217-expresswire-fix-v2-1-4a02b10acd96@dujemihanovic.xyz>
Date: Wed, 17 Dec 2025 19:14:23 +0100
From: Duje Mihanović <dujemihanovic32@...il.com>
To: Lee Jones <lee@...nel.org>, Pavel Machek <pavel@...nel.org>, 
 Linus Walleij <linus.walleij@...aro.org>, 
 Daniel Thompson <daniel.thompson@...aro.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 v2] leds: expresswire: Fix chip state breakage

From: Duje Mihanović <duje@...emihanovic.xyz>

It is possible to put the KTD2801 chip in an unknown/undefined state by
changing the brightness very rapidly (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 talking to the chip. While at it,
make expresswire_power_off() use fsleep() and also unexport some
functions meant to be internal.

Fixes: 1368d06dd2c9 ("leds: Introduce ExpressWire library")
Tested-by: Karel Balej <balejk@...fyz.cz>
Signed-off-by: Duje Mihanović <duje@...emihanovic.xyz>
---
Changes in v2:
- Update trailers
- Rebase on v6.19-rc1
- Reword commit message (fix grammar errors, simplify text)
- Add Fixes: tag
- Link to v1: https://lore.kernel.org/r/20250829-expresswire-fix-v1-1-f8c8c6ad6c5f@dujemihanovic.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 bb69be228a6d..25c6b159a6ee 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 a422921f4159..7f8c4795f69f 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: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
change-id: 20250829-expresswire-fix-663d1b3c32aa

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