| 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/core/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 | |
| 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 | |
| 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 | |
| 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 | |
| 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 | |
| 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 | |
| 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 | |
| 141 | static void pcf8574_class_init(ObjectClass *klass, const 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 | device_class_set_legacy_reset(dc, 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); |