1 /* SPDX-License-Identifier: GPL-2.0-only */
2
3 /*
4 * NXP PCF8574 8-port I2C GPIO expansion chip.
5 * Copyright (c) 2024 KNS Group (YADRO).
6 * Written by Dmitrii Sharikhin <d.sharikhin@yadro.com>
7 */
8
9 #include "qemu/osdep.h"
10 #include "hw/i2c/i2c.h"
11 #include "hw/gpio/pcf8574.h"
12 #include "hw/irq.h"
13 #include "migration/vmstate.h"
14 #include "qemu/log.h"
15 #include "qemu/module.h"
16 #include "qom/object.h"
17
18 /*
19 * PCF8574 and compatible chips incorporate quasi-bidirectional
20 * IO. Electrically it means that device sustain pull-up to line
21 * unless IO port is configured as output _and_ driven low.
22 *
23 * IO access is implemented as simple I2C single-byte read
24 * or write operation. So, to configure line to input user write 1
25 * to corresponding bit. To configure line to output and drive it low
26 * user write 0 to corresponding bit.
27 *
28 * In essence, user can think of quasi-bidirectional IO as
29 * open-drain line, except presence of builtin rising edge acceleration
30 * embedded in PCF8574 IC
31 *
32 * PCF8574 has interrupt request line, which is being pulled down when
33 * port line state differs from last read. Port read operation clears
34 * state and INT line returns to high state via pullup.
35 */
36
37 OBJECT_DECLARE_SIMPLE_TYPE(PCF8574State, PCF8574)
38
39 #define PORTS_COUNT (8)
40
41 struct PCF8574State {
42 I2CSlave parent_obj;
43 uint8_t lastrq; /* Last requested state. If changed - assert irq */
44 uint8_t input; /* external electrical line state */
45 uint8_t output; /* Pull-up (1) or drive low (0) on bit */
46 qemu_irq handler[PORTS_COUNT];
47 qemu_irq intrq; /* External irq request */
48 };
49
pcf8574_reset(DeviceState * dev)50 static void pcf8574_reset(DeviceState *dev)
51 {
52 PCF8574State *s = PCF8574(dev);
53 s->lastrq = MAKE_64BIT_MASK(0, PORTS_COUNT);
54 s->input = MAKE_64BIT_MASK(0, PORTS_COUNT);
55 s->output = MAKE_64BIT_MASK(0, PORTS_COUNT);
56 }
57
pcf8574_line_state(PCF8574State * s)58 static inline uint8_t pcf8574_line_state(PCF8574State *s)
59 {
60 /* we driving line low or external circuit does that */
61 return s->input & s->output;
62 }
63
pcf8574_rx(I2CSlave * i2c)64 static uint8_t pcf8574_rx(I2CSlave *i2c)
65 {
66 PCF8574State *s = PCF8574(i2c);
67 uint8_t linestate = pcf8574_line_state(s);
68 if (s->lastrq != linestate) {
69 s->lastrq = linestate;
70 if (s->intrq) {
71 qemu_set_irq(s->intrq, 1);
72 }
73 }
74 return linestate;
75 }
76
pcf8574_tx(I2CSlave * i2c,uint8_t data)77 static int pcf8574_tx(I2CSlave *i2c, uint8_t data)
78 {
79 PCF8574State *s = PCF8574(i2c);
80 uint8_t prev;
81 uint8_t diff;
82 uint8_t actual;
83 int line = 0;
84
85 prev = pcf8574_line_state(s);
86 s->output = data;
87 actual = pcf8574_line_state(s);
88
89 for (diff = (actual ^ prev); diff; diff &= ~(1 << line)) {
90 line = ctz32(diff);
91 if (s->handler[line]) {
92 qemu_set_irq(s->handler[line], (actual >> line) & 1);
93 }
94 }
95
96 if (s->intrq) {
97 qemu_set_irq(s->intrq, actual == s->lastrq);
98 }
99
100 return 0;
101 }
102
103 static const VMStateDescription vmstate_pcf8574 = {
104 .name = "pcf8574",
105 .version_id = 0,
106 .minimum_version_id = 0,
107 .fields = (VMStateField[]) {
108 VMSTATE_I2C_SLAVE(parent_obj, PCF8574State),
109 VMSTATE_UINT8(lastrq, PCF8574State),
110 VMSTATE_UINT8(input, PCF8574State),
111 VMSTATE_UINT8(output, PCF8574State),
112 VMSTATE_END_OF_LIST()
113 }
114 };
115
pcf8574_gpio_set(void * opaque,int line,int level)116 static void pcf8574_gpio_set(void *opaque, int line, int level)
117 {
118 PCF8574State *s = (PCF8574State *) opaque;
119 assert(line >= 0 && line < ARRAY_SIZE(s->handler));
120
121 if (level) {
122 s->input |= (1 << line);
123 } else {
124 s->input &= ~(1 << line);
125 }
126
127 if (pcf8574_line_state(s) != s->lastrq && s->intrq) {
128 qemu_set_irq(s->intrq, 0);
129 }
130 }
131
pcf8574_realize(DeviceState * dev,Error ** errp)132 static void pcf8574_realize(DeviceState *dev, Error **errp)
133 {
134 PCF8574State *s = PCF8574(dev);
135
136 qdev_init_gpio_in(dev, pcf8574_gpio_set, ARRAY_SIZE(s->handler));
137 qdev_init_gpio_out(dev, s->handler, ARRAY_SIZE(s->handler));
138 qdev_init_gpio_out_named(dev, &s->intrq, "nINT", 1);
139 }
140
pcf8574_class_init(ObjectClass * klass,void * data)141 static void pcf8574_class_init(ObjectClass *klass, void *data)
142 {
143 DeviceClass *dc = DEVICE_CLASS(klass);
144 I2CSlaveClass *k = I2C_SLAVE_CLASS(klass);
145
146 k->recv = pcf8574_rx;
147 k->send = pcf8574_tx;
148 dc->realize = pcf8574_realize;
149 dc->reset = pcf8574_reset;
150 dc->vmsd = &vmstate_pcf8574;
151 }
152
153 static const TypeInfo pcf8574_infos[] = {
154 {
155 .name = TYPE_PCF8574,
156 .parent = TYPE_I2C_SLAVE,
157 .instance_size = sizeof(PCF8574State),
158 .class_init = pcf8574_class_init,
159 }
160 };
161
162 DEFINE_TYPES(pcf8574_infos);
163