1 | /* |
2 | * Bit-Bang i2c emulation extracted from |
3 | * Marvell MV88W8618 / Freecom MusicPal emulation. |
4 | * |
5 | * Copyright (c) 2008 Jan Kiszka |
6 | * |
7 | * This code is licensed under the GNU GPL v2. |
8 | * |
9 | * Contributions after 2012-01-13 are licensed under the terms of the |
10 | * GNU GPL, version 2 or (at your option) any later version. |
11 | */ |
12 | |
13 | #include "qemu/osdep.h" |
14 | #include "hw/irq.h" |
15 | #include "hw/i2c/bitbang_i2c.h" |
16 | #include "hw/sysbus.h" |
17 | #include "qemu/module.h" |
18 | |
19 | //#define DEBUG_BITBANG_I2C |
20 | |
21 | #ifdef DEBUG_BITBANG_I2C |
22 | #define DPRINTF(fmt, ...) \ |
23 | do { printf("bitbang_i2c: " fmt , ## __VA_ARGS__); } while (0) |
24 | #else |
25 | #define DPRINTF(fmt, ...) do {} while(0) |
26 | #endif |
27 | |
28 | static void bitbang_i2c_enter_stop(bitbang_i2c_interface *i2c) |
29 | { |
30 | DPRINTF("STOP\n" ); |
31 | if (i2c->current_addr >= 0) |
32 | i2c_end_transfer(i2c->bus); |
33 | i2c->current_addr = -1; |
34 | i2c->state = STOPPED; |
35 | } |
36 | |
37 | /* Set device data pin. */ |
38 | static int bitbang_i2c_ret(bitbang_i2c_interface *i2c, int level) |
39 | { |
40 | i2c->device_out = level; |
41 | //DPRINTF("%d %d %d\n", i2c->last_clock, i2c->last_data, i2c->device_out); |
42 | return level & i2c->last_data; |
43 | } |
44 | |
45 | /* Leave device data pin unodified. */ |
46 | static int bitbang_i2c_nop(bitbang_i2c_interface *i2c) |
47 | { |
48 | return bitbang_i2c_ret(i2c, i2c->device_out); |
49 | } |
50 | |
51 | /* Returns data line level. */ |
52 | int bitbang_i2c_set(bitbang_i2c_interface *i2c, int line, int level) |
53 | { |
54 | int data; |
55 | |
56 | if (level != 0 && level != 1) { |
57 | abort(); |
58 | } |
59 | |
60 | if (line == BITBANG_I2C_SDA) { |
61 | if (level == i2c->last_data) { |
62 | return bitbang_i2c_nop(i2c); |
63 | } |
64 | i2c->last_data = level; |
65 | if (i2c->last_clock == 0) { |
66 | return bitbang_i2c_nop(i2c); |
67 | } |
68 | if (level == 0) { |
69 | DPRINTF("START\n" ); |
70 | /* START condition. */ |
71 | i2c->state = SENDING_BIT7; |
72 | i2c->current_addr = -1; |
73 | } else { |
74 | /* STOP condition. */ |
75 | bitbang_i2c_enter_stop(i2c); |
76 | } |
77 | return bitbang_i2c_ret(i2c, 1); |
78 | } |
79 | |
80 | data = i2c->last_data; |
81 | if (i2c->last_clock == level) { |
82 | return bitbang_i2c_nop(i2c); |
83 | } |
84 | i2c->last_clock = level; |
85 | if (level == 0) { |
86 | /* State is set/read at the start of the clock pulse. |
87 | release the data line at the end. */ |
88 | return bitbang_i2c_ret(i2c, 1); |
89 | } |
90 | switch (i2c->state) { |
91 | case STOPPED: |
92 | case SENT_NACK: |
93 | return bitbang_i2c_ret(i2c, 1); |
94 | |
95 | case SENDING_BIT7 ... SENDING_BIT0: |
96 | i2c->buffer = (i2c->buffer << 1) | data; |
97 | /* will end up in WAITING_FOR_ACK */ |
98 | i2c->state++; |
99 | return bitbang_i2c_ret(i2c, 1); |
100 | |
101 | case WAITING_FOR_ACK: |
102 | { |
103 | int ret; |
104 | |
105 | if (i2c->current_addr < 0) { |
106 | i2c->current_addr = i2c->buffer; |
107 | DPRINTF("Address 0x%02x\n" , i2c->current_addr); |
108 | ret = i2c_start_transfer(i2c->bus, i2c->current_addr >> 1, |
109 | i2c->current_addr & 1); |
110 | } else { |
111 | DPRINTF("Sent 0x%02x\n" , i2c->buffer); |
112 | ret = i2c_send(i2c->bus, i2c->buffer); |
113 | } |
114 | if (ret) { |
115 | /* NACK (either addressing a nonexistent device, or the |
116 | * device we were sending to decided to NACK us). |
117 | */ |
118 | DPRINTF("Got NACK\n" ); |
119 | bitbang_i2c_enter_stop(i2c); |
120 | return bitbang_i2c_ret(i2c, 1); |
121 | } |
122 | if (i2c->current_addr & 1) { |
123 | i2c->state = RECEIVING_BIT7; |
124 | } else { |
125 | i2c->state = SENDING_BIT7; |
126 | } |
127 | return bitbang_i2c_ret(i2c, 0); |
128 | } |
129 | case RECEIVING_BIT7: |
130 | i2c->buffer = i2c_recv(i2c->bus); |
131 | DPRINTF("RX byte 0x%02x\n" , i2c->buffer); |
132 | /* Fall through... */ |
133 | case RECEIVING_BIT6 ... RECEIVING_BIT0: |
134 | data = i2c->buffer >> 7; |
135 | /* will end up in SENDING_ACK */ |
136 | i2c->state++; |
137 | i2c->buffer <<= 1; |
138 | return bitbang_i2c_ret(i2c, data); |
139 | |
140 | case SENDING_ACK: |
141 | i2c->state = RECEIVING_BIT7; |
142 | if (data != 0) { |
143 | DPRINTF("NACKED\n" ); |
144 | i2c->state = SENT_NACK; |
145 | i2c_nack(i2c->bus); |
146 | } else { |
147 | DPRINTF("ACKED\n" ); |
148 | } |
149 | return bitbang_i2c_ret(i2c, 1); |
150 | } |
151 | abort(); |
152 | } |
153 | |
154 | void bitbang_i2c_init(bitbang_i2c_interface *s, I2CBus *bus) |
155 | { |
156 | s->bus = bus; |
157 | s->last_data = 1; |
158 | s->last_clock = 1; |
159 | s->device_out = 1; |
160 | } |
161 | |
162 | /* GPIO interface. */ |
163 | |
164 | #define TYPE_GPIO_I2C "gpio_i2c" |
165 | #define GPIO_I2C(obj) OBJECT_CHECK(GPIOI2CState, (obj), TYPE_GPIO_I2C) |
166 | |
167 | typedef struct GPIOI2CState { |
168 | SysBusDevice parent_obj; |
169 | |
170 | MemoryRegion dummy_iomem; |
171 | bitbang_i2c_interface bitbang; |
172 | int last_level; |
173 | qemu_irq out; |
174 | } GPIOI2CState; |
175 | |
176 | static void bitbang_i2c_gpio_set(void *opaque, int irq, int level) |
177 | { |
178 | GPIOI2CState *s = opaque; |
179 | |
180 | level = bitbang_i2c_set(&s->bitbang, irq, level); |
181 | if (level != s->last_level) { |
182 | s->last_level = level; |
183 | qemu_set_irq(s->out, level); |
184 | } |
185 | } |
186 | |
187 | static void gpio_i2c_init(Object *obj) |
188 | { |
189 | DeviceState *dev = DEVICE(obj); |
190 | GPIOI2CState *s = GPIO_I2C(obj); |
191 | SysBusDevice *sbd = SYS_BUS_DEVICE(obj); |
192 | I2CBus *bus; |
193 | |
194 | memory_region_init(&s->dummy_iomem, obj, "gpio_i2c" , 0); |
195 | sysbus_init_mmio(sbd, &s->dummy_iomem); |
196 | |
197 | bus = i2c_init_bus(dev, "i2c" ); |
198 | bitbang_i2c_init(&s->bitbang, bus); |
199 | |
200 | qdev_init_gpio_in(dev, bitbang_i2c_gpio_set, 2); |
201 | qdev_init_gpio_out(dev, &s->out, 1); |
202 | } |
203 | |
204 | static void gpio_i2c_class_init(ObjectClass *klass, void *data) |
205 | { |
206 | DeviceClass *dc = DEVICE_CLASS(klass); |
207 | |
208 | set_bit(DEVICE_CATEGORY_BRIDGE, dc->categories); |
209 | dc->desc = "Virtual GPIO to I2C bridge" ; |
210 | } |
211 | |
212 | static const TypeInfo gpio_i2c_info = { |
213 | .name = TYPE_GPIO_I2C, |
214 | .parent = TYPE_SYS_BUS_DEVICE, |
215 | .instance_size = sizeof(GPIOI2CState), |
216 | .instance_init = gpio_i2c_init, |
217 | .class_init = gpio_i2c_class_init, |
218 | }; |
219 | |
220 | static void bitbang_i2c_register_types(void) |
221 | { |
222 | type_register_static(&gpio_i2c_info); |
223 | } |
224 | |
225 | type_init(bitbang_i2c_register_types) |
226 | |