leds-expresswire.c

 1// SPDX-License-Identifier: GPL-2.0-only
 2/*
 3 * Shared library for Kinetic's ExpressWire protocol.
 4 * This protocol works by pulsing the ExpressWire IC's control GPIO.
 5 * ktd2692 and ktd2801 are known to use this protocol.
 6 */
 7
 8#include <linux/bits.h>
 9#include <linux/delay.h>
10#include <linux/export.h>
11#include <linux/gpio/consumer.h>
12#include <linux/irqflags.h>
13#include <linux/types.h>
14
15#include <linux/leds-expresswire.h>
16
17void expresswire_power_off(struct expresswire_common_props *props)
18{
19	gpiod_set_value_cansleep(props->ctrl_gpio, 0);
20	fsleep(props->timing.poweroff_us);
21}
22EXPORT_SYMBOL_NS_GPL(expresswire_power_off, "EXPRESSWIRE");
23
24void expresswire_enable(struct expresswire_common_props *props)
25{
26	unsigned long flags;
27
28	local_irq_save(flags);
29
30	gpiod_set_value(props->ctrl_gpio, 1);
31	udelay(props->timing.detect_delay_us);
32	gpiod_set_value(props->ctrl_gpio, 0);
33	udelay(props->timing.detect_us);
34	gpiod_set_value(props->ctrl_gpio, 1);
35
36	local_irq_restore(flags);
37}
38EXPORT_SYMBOL_NS_GPL(expresswire_enable, "EXPRESSWIRE");
39
40static void expresswire_start(struct expresswire_common_props *props)
41{
42	gpiod_set_value(props->ctrl_gpio, 1);
43	udelay(props->timing.data_start_us);
44}
45
46static void expresswire_end(struct expresswire_common_props *props)
47{
48	gpiod_set_value(props->ctrl_gpio, 0);
49	udelay(props->timing.end_of_data_low_us);
50	gpiod_set_value(props->ctrl_gpio, 1);
51	udelay(props->timing.end_of_data_high_us);
52}
53
54static void expresswire_set_bit(struct expresswire_common_props *props, bool bit)
55{
56	if (bit) {
57		gpiod_set_value(props->ctrl_gpio, 0);
58		udelay(props->timing.short_bitset_us);
59		gpiod_set_value(props->ctrl_gpio, 1);
60		udelay(props->timing.long_bitset_us);
61	} else {
62		gpiod_set_value(props->ctrl_gpio, 0);
63		udelay(props->timing.long_bitset_us);
64		gpiod_set_value(props->ctrl_gpio, 1);
65		udelay(props->timing.short_bitset_us);
66	}
67}
68
69void expresswire_write_u8(struct expresswire_common_props *props, u8 val)
70{
71	unsigned long flags;
72
73	local_irq_save(flags);
74
75	expresswire_start(props);
76	for (int i = 7; i >= 0; i--)
77		expresswire_set_bit(props, val & BIT(i));
78	expresswire_end(props);
79
80	local_irq_restore(flags);
81}
82EXPORT_SYMBOL_NS_GPL(expresswire_write_u8, "EXPRESSWIRE");