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leds: expresswire: Fix chip state breakage

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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: 1368d06dd2 ("leds: Introduce ExpressWire library")
Tested-by: Karel Balej <balejk@matfyz.cz>
Signed-off-by: Duje Mihanović <duje@dujemihanovic.xyz>
Link: https://patch.msgid.link/20251217-expresswire-fix-v2-1-4a02b10acd96@dujemihanovic.xyz
Signed-off-by: Lee Jones <lee@kernel.org>
This commit is contained in:
Duje Mihanović 2025-12-17 19:14:23 +01:00 • committed by Lee Jones
parent 393d56d437
commit f4b830a537
2 changed files with 17 additions and 10 deletions
Download patch file Download diff file Expand all files Collapse all files

24
drivers/leds/leds-expresswire.c
View file

@ -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");

3
include/linux/leds-expresswire.h
View file

@ -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 */