qemu

i2c_mux_pca954x.c (6289B)

---

 /*
  * I2C multiplexer for PCA954x series of I2C multiplexer/switch chips.
  *
  * Copyright 2021 Google LLC
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the
  * Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful, but WITHOUT
  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
  * for more details.
  */
 
 #include "qemu/osdep.h"
 #include "qapi/error.h"
 #include "hw/i2c/i2c.h"
 #include "hw/i2c/i2c_mux_pca954x.h"
 #include "hw/i2c/smbus_slave.h"
 #include "hw/qdev-core.h"
 #include "hw/sysbus.h"
 #include "qemu/log.h"
 #include "qemu/module.h"
 #include "qemu/queue.h"
 #include "qom/object.h"
 #include "trace.h"
 
 #define PCA9548_CHANNEL_COUNT 8
 #define PCA9546_CHANNEL_COUNT 4
 
 /*
  * struct Pca954xState - The pca954x state object.
  * @control: The value written to the mux control.
  * @channel: The set of i2c channel buses that act as channels which own the
  * i2c children.
  */
 typedef struct Pca954xState {
     SMBusDevice parent;
 
     uint8_t control;
 
     bool enabled[PCA9548_CHANNEL_COUNT];
     I2CBus *bus[PCA9548_CHANNEL_COUNT];
 } Pca954xState;
 
 /*
  * struct Pca954xClass - The pca954x class object.
  * @nchans: The number of i2c channels this device has.
  */
 typedef struct Pca954xClass {
     SMBusDeviceClass parent;
 
     uint8_t nchans;
 } Pca954xClass;
 
 #define TYPE_PCA954X "pca954x"
 OBJECT_DECLARE_TYPE(Pca954xState, Pca954xClass, PCA954X)
 
 /*
  * For each channel, if it's enabled, recursively call match on those children.
  */
 static bool pca954x_match(I2CSlave *candidate, uint8_t address,
                           bool broadcast,
                           I2CNodeList *current_devs)
 {
     Pca954xState *mux = PCA954X(candidate);
     Pca954xClass *mc = PCA954X_GET_CLASS(mux);
     int i;
 
     /* They are talking to the mux itself (or all devices enabled). */
     if ((candidate->address == address) || broadcast) {
         I2CNode *node = g_new(struct I2CNode, 1);
         node->elt = candidate;
         QLIST_INSERT_HEAD(current_devs, node, next);
         if (!broadcast) {
             return true;
         }
     }
 
     for (i = 0; i < mc->nchans; i++) {
         if (!mux->enabled[i]) {
             continue;
         }
 
         if (i2c_scan_bus(mux->bus[i], address, broadcast,
                          current_devs)) {
             if (!broadcast) {
                 return true;
             }
         }
     }
 
     /* If we arrived here we didn't find a match, return broadcast. */
     return broadcast;
 }
 
 static void pca954x_enable_channel(Pca954xState *s, uint8_t enable_mask)
 {
     Pca954xClass *mc = PCA954X_GET_CLASS(s);
     int i;
 
     /*
      * For each channel, check if their bit is set in enable_mask and if yes,
      * enable it, otherwise disable, hide it.
      */
     for (i = 0; i < mc->nchans; i++) {
         if (enable_mask & (1 << i)) {
             s->enabled[i] = true;
         } else {
             s->enabled[i] = false;
         }
     }
 }
 
 static void pca954x_write(Pca954xState *s, uint8_t data)
 {
     s->control = data;
     pca954x_enable_channel(s, data);
 
     trace_pca954x_write_bytes(data);
 }
 
 static int pca954x_write_data(SMBusDevice *d, uint8_t *buf, uint8_t len)
 {
     Pca954xState *s = PCA954X(d);
 
     if (len == 0) {
         qemu_log_mask(LOG_GUEST_ERROR, "%s: writing empty data\n", __func__);
         return -1;
     }
 
     /*
      * len should be 1, because they write one byte to enable/disable channels.
      */
     if (len > 1) {
         qemu_log_mask(LOG_GUEST_ERROR,
             "%s: extra data after channel selection mask\n",
             __func__);
         return -1;
     }
 
     pca954x_write(s, buf[0]);
     return 0;
 }
 
 static uint8_t pca954x_read_byte(SMBusDevice *d)
 {
     Pca954xState *s = PCA954X(d);
     uint8_t data = s->control;
     trace_pca954x_read_data(data);
     return data;
 }
 
 static void pca954x_enter_reset(Object *obj, ResetType type)
 {
     Pca954xState *s = PCA954X(obj);
     /* Reset will disable all channels. */
     pca954x_write(s, 0);
 }
 
 I2CBus *pca954x_i2c_get_bus(I2CSlave *mux, uint8_t channel)
 {
     Pca954xClass *pc = PCA954X_GET_CLASS(mux);
     Pca954xState *pca954x = PCA954X(mux);
 
     g_assert(channel < pc->nchans);
     return pca954x->bus[channel];
 }
 
 static void pca9546_class_init(ObjectClass *klass, void *data)
 {
     Pca954xClass *s = PCA954X_CLASS(klass);
     s->nchans = PCA9546_CHANNEL_COUNT;
 }
 
 static void pca9548_class_init(ObjectClass *klass, void *data)
 {
     Pca954xClass *s = PCA954X_CLASS(klass);
     s->nchans = PCA9548_CHANNEL_COUNT;
 }
 
 static void pca954x_init(Object *obj)
 {
     Pca954xState *s = PCA954X(obj);
     Pca954xClass *c = PCA954X_GET_CLASS(obj);
     int i;
 
     /* SMBus modules. Cannot fail. */
     for (i = 0; i < c->nchans; i++) {
         g_autofree gchar *bus_name = g_strdup_printf("i2c.%d", i);
 
         /* start all channels as disabled. */
         s->enabled[i] = false;
         s->bus[i] = i2c_init_bus(DEVICE(s), bus_name);
     }
 }
 
 static void pca954x_class_init(ObjectClass *klass, void *data)
 {
     I2CSlaveClass *sc = I2C_SLAVE_CLASS(klass);
     ResettableClass *rc = RESETTABLE_CLASS(klass);
     DeviceClass *dc = DEVICE_CLASS(klass);
     SMBusDeviceClass *k = SMBUS_DEVICE_CLASS(klass);
 
     sc->match_and_add = pca954x_match;
 
     rc->phases.enter = pca954x_enter_reset;
 
     dc->desc = "Pca954x i2c-mux";
 
     k->write_data = pca954x_write_data;
     k->receive_byte = pca954x_read_byte;
 }
 
 static const TypeInfo pca954x_info[] = {
     {
         .name          = TYPE_PCA954X,
         .parent        = TYPE_SMBUS_DEVICE,
         .instance_size = sizeof(Pca954xState),
         .instance_init = pca954x_init,
         .class_size    = sizeof(Pca954xClass),
         .class_init    = pca954x_class_init,
         .abstract      = true,
     },
     {
         .name          = TYPE_PCA9546,
         .parent        = TYPE_PCA954X,
         .class_init    = pca9546_class_init,
     },
     {
         .name          = TYPE_PCA9548,
         .parent        = TYPE_PCA954X,
         .class_init    = pca9548_class_init,
     },
 };
 
 DEFINE_TYPES(pca954x_info)