xref: /openbmc/qemu/hw/i2c/i2c_mux_pca954x.c (revision 7d87775f) 
1 /*
2  * I2C multiplexer for PCA954x series of I2C multiplexer/switch chips.
3  *
4  * Copyright 2021 Google LLC
5  *
6  * This program is free software; you can redistribute it and/or modify it
7  * under the terms of the GNU General Public License as published by the
8  * Free Software Foundation; either version 2 of the License, or
9  * (at your option) any later version.
10  *
11  * This program is distributed in the hope that it will be useful, but WITHOUT
12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14  * for more details.
15  */
16 
17 #include "qemu/osdep.h"
18 #include "qapi/error.h"
19 #include "hw/i2c/i2c.h"
20 #include "hw/i2c/i2c_mux_pca954x.h"
21 #include "hw/i2c/smbus_slave.h"
22 #include "hw/qdev-core.h"
23 #include "hw/qdev-properties.h"
24 #include "hw/sysbus.h"
25 #include "qemu/log.h"
26 #include "qemu/module.h"
27 #include "qemu/queue.h"
28 #include "qom/object.h"
29 #include "trace.h"
30 
31 #define PCA9548_CHANNEL_COUNT 8
32 #define PCA9546_CHANNEL_COUNT 4
33 
34 /*
35  * struct Pca954xState - The pca954x state object.
36  * @control: The value written to the mux control.
37  * @channel: The set of i2c channel buses that act as channels which own the
38  * i2c children.
39  */
40 typedef struct Pca954xState {
41     SMBusDevice parent;
42 
43     uint8_t control;
44 
45     bool enabled[PCA9548_CHANNEL_COUNT];
46     I2CBus *bus[PCA9548_CHANNEL_COUNT];
47 
48     char *name;
49 } Pca954xState;
50 
51 /*
52  * struct Pca954xClass - The pca954x class object.
53  * @nchans: The number of i2c channels this device has.
54  */
55 typedef struct Pca954xClass {
56     SMBusDeviceClass parent;
57 
58     uint8_t nchans;
59 } Pca954xClass;
60 
61 #define TYPE_PCA954X "pca954x"
62 OBJECT_DECLARE_TYPE(Pca954xState, Pca954xClass, PCA954X)
63 
64 /*
65  * For each channel, if it's enabled, recursively call match on those children.
66  */
67 static bool pca954x_match(I2CSlave *candidate, uint8_t address,
68                           bool broadcast,
69                           I2CNodeList *current_devs)
70 {
71     Pca954xState *mux = PCA954X(candidate);
72     Pca954xClass *mc = PCA954X_GET_CLASS(mux);
73     int i;
74 
75     /* They are talking to the mux itself (or all devices enabled). */
76     if ((candidate->address == address) || broadcast) {
77         I2CNode *node = g_new(struct I2CNode, 1);
78         node->elt = candidate;
79         QLIST_INSERT_HEAD(current_devs, node, next);
80         if (!broadcast) {
81             return true;
82         }
83     }
84 
85     for (i = 0; i < mc->nchans; i++) {
86         if (!mux->enabled[i]) {
87             continue;
88         }
89 
90         if (i2c_scan_bus(mux->bus[i], address, broadcast,
91                          current_devs)) {
92             if (!broadcast) {
93                 return true;
94             }
95         }
96     }
97 
98     /* If we arrived here we didn't find a match, return broadcast. */
99     return broadcast;
100 }
101 
102 static void pca954x_enable_channel(Pca954xState *s, uint8_t enable_mask)
103 {
104     Pca954xClass *mc = PCA954X_GET_CLASS(s);
105     int i;
106 
107     /*
108      * For each channel, check if their bit is set in enable_mask and if yes,
109      * enable it, otherwise disable, hide it.
110      */
111     for (i = 0; i < mc->nchans; i++) {
112         if (enable_mask & (1 << i)) {
113             s->enabled[i] = true;
114         } else {
115             s->enabled[i] = false;
116         }
117     }
118 }
119 
120 static void pca954x_write(Pca954xState *s, uint8_t data)
121 {
122     s->control = data;
123     pca954x_enable_channel(s, data);
124 
125     trace_pca954x_write_bytes(data);
126 }
127 
128 static int pca954x_write_data(SMBusDevice *d, uint8_t *buf, uint8_t len)
129 {
130     Pca954xState *s = PCA954X(d);
131 
132     if (len == 0) {
133         qemu_log_mask(LOG_GUEST_ERROR, "%s: writing empty data\n", __func__);
134         return -1;
135     }
136 
137     /*
138      * len should be 1, because they write one byte to enable/disable channels.
139      */
140     if (len > 1) {
141         qemu_log_mask(LOG_GUEST_ERROR,
142             "%s: extra data after channel selection mask\n",
143             __func__);
144         return -1;
145     }
146 
147     pca954x_write(s, buf[0]);
148     return 0;
149 }
150 
151 static uint8_t pca954x_read_byte(SMBusDevice *d)
152 {
153     Pca954xState *s = PCA954X(d);
154     uint8_t data = s->control;
155     trace_pca954x_read_data(data);
156     return data;
157 }
158 
159 static void pca954x_enter_reset(Object *obj, ResetType type)
160 {
161     Pca954xState *s = PCA954X(obj);
162     /* Reset will disable all channels. */
163     pca954x_write(s, 0);
164 }
165 
166 I2CBus *pca954x_i2c_get_bus(I2CSlave *mux, uint8_t channel)
167 {
168     Pca954xClass *pc = PCA954X_GET_CLASS(mux);
169     Pca954xState *pca954x = PCA954X(mux);
170 
171     g_assert(channel < pc->nchans);
172     return pca954x->bus[channel];
173 }
174 
175 static void pca9546_class_init(ObjectClass *klass, void *data)
176 {
177     Pca954xClass *s = PCA954X_CLASS(klass);
178     s->nchans = PCA9546_CHANNEL_COUNT;
179 }
180 
181 static void pca9548_class_init(ObjectClass *klass, void *data)
182 {
183     Pca954xClass *s = PCA954X_CLASS(klass);
184     s->nchans = PCA9548_CHANNEL_COUNT;
185 }
186 
187 static void pca954x_realize(DeviceState *dev, Error **errp)
188 {
189     Pca954xState *s = PCA954X(dev);
190     DeviceState *d = DEVICE(s);
191     if (s->name) {
192         d->id = g_strdup(s->name);
193     } else {
194         d->id = g_strdup_printf("pca954x[%x]", s->parent.i2c.address);
195     }
196 }
197 
198 static void pca954x_init(Object *obj)
199 {
200     Pca954xState *s = PCA954X(obj);
201     Pca954xClass *c = PCA954X_GET_CLASS(obj);
202     int i;
203 
204     /* SMBus modules. Cannot fail. */
205     for (i = 0; i < c->nchans; i++) {
206         g_autofree gchar *bus_name = g_strdup_printf("i2c.%d", i);
207 
208         /* start all channels as disabled. */
209         s->enabled[i] = false;
210         s->bus[i] = i2c_init_bus(DEVICE(s), bus_name);
211     }
212 }
213 
214 static Property pca954x_props[] = {
215     DEFINE_PROP_STRING("name", Pca954xState, name),
216     DEFINE_PROP_END_OF_LIST()
217 };
218 
219 static void pca954x_class_init(ObjectClass *klass, void *data)
220 {
221     I2CSlaveClass *sc = I2C_SLAVE_CLASS(klass);
222     ResettableClass *rc = RESETTABLE_CLASS(klass);
223     DeviceClass *dc = DEVICE_CLASS(klass);
224     SMBusDeviceClass *k = SMBUS_DEVICE_CLASS(klass);
225 
226     sc->match_and_add = pca954x_match;
227 
228     rc->phases.enter = pca954x_enter_reset;
229 
230     dc->desc = "Pca954x i2c-mux";
231     dc->realize = pca954x_realize;
232 
233     k->write_data = pca954x_write_data;
234     k->receive_byte = pca954x_read_byte;
235 
236     device_class_set_props(dc, pca954x_props);
237 }
238 
239 static const TypeInfo pca954x_info[] = {
240     {
241         .name          = TYPE_PCA954X,
242         .parent        = TYPE_SMBUS_DEVICE,
243         .instance_size = sizeof(Pca954xState),
244         .instance_init = pca954x_init,
245         .class_size    = sizeof(Pca954xClass),
246         .class_init    = pca954x_class_init,
247         .abstract      = true,
248     },
249     {
250         .name          = TYPE_PCA9546,
251         .parent        = TYPE_PCA954X,
252         .class_init    = pca9546_class_init,
253     },
254     {
255         .name          = TYPE_PCA9548,
256         .parent        = TYPE_PCA954X,
257         .class_init    = pca9548_class_init,
258     },
259 };
260 
261 DEFINE_TYPES(pca954x_info)
262