hw/i2c/aspeed: add slave device in old register mode

Add slave mode functionality for the Aspeed I2C controller in old
register mode. This is implemented by realizing an I2C slave device
owned by the I2C controller and attached to its own bus.

The I2C slave device only implements asynchronous sends on the bus, so
slaves not supporting that will not be able to communicate with it.

Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
[ clg: checkpatch fixes ]
Message-Id: <20220601210831.67259-6-its@irrelevant.dk>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20220630045133.32251-7-me@pjd.dev>
Signed-off-by: Cédric Le Goater <clg@kaod.org>

hw/i2c/aspeed_i2c.c

@@ -696,9 +696,7 @@ static void aspeed_i2c_bus_old_write(AspeedI2CBus *bus, hwaddr offset,
     switch (offset) {
     case A_I2CD_FUN_CTRL:
         if (SHARED_FIELD_EX32(value, SLAVE_EN)) {
-            qemu_log_mask(LOG_UNIMP, "%s: slave mode not implemented\n",
-                          __func__);
-            break;
+            i2c_slave_set_address(bus->slave, bus->regs[R_I2CD_DEV_ADDR]);
         }
         bus->regs[R_I2CD_FUN_CTRL] = value & 0x0071C3FF;
         break;
@@ -719,12 +717,15 @@ static void aspeed_i2c_bus_old_write(AspeedI2CBus *bus, hwaddr offset,
             bus->controller->intr_status &= ~(1 << bus->id);
             qemu_irq_lower(aic->bus_get_irq(bus));
         }
-        if (handle_rx && (SHARED_ARRAY_FIELD_EX32(bus->regs, R_I2CD_CMD,
-                                                  M_RX_CMD) ||
-                      SHARED_ARRAY_FIELD_EX32(bus->regs, R_I2CD_CMD,
-                                              M_S_RX_CMD_LAST))) {
-            aspeed_i2c_handle_rx_cmd(bus);
-            aspeed_i2c_bus_raise_interrupt(bus);
+        if (handle_rx) {
+            if (SHARED_ARRAY_FIELD_EX32(bus->regs, R_I2CD_CMD, M_RX_CMD) ||
+                SHARED_ARRAY_FIELD_EX32(bus->regs, R_I2CD_CMD,
+                                        M_S_RX_CMD_LAST)) {
+                aspeed_i2c_handle_rx_cmd(bus);
+                aspeed_i2c_bus_raise_interrupt(bus);
+            } else if (aspeed_i2c_get_state(bus) == I2CD_STXD) {
+                i2c_ack(bus->bus);
+            }
         }
         break;
     case A_I2CD_DEV_ADDR:
@@ -1036,6 +1037,73 @@ static const TypeInfo aspeed_i2c_info = {
     .abstract   = true,
 };
 
+static int aspeed_i2c_bus_slave_event(I2CSlave *slave, enum i2c_event event)
+{
+    BusState *qbus = qdev_get_parent_bus(DEVICE(slave));
+    AspeedI2CBus *bus = ASPEED_I2C_BUS(qbus->parent);
+    uint32_t reg_intr_sts = aspeed_i2c_bus_intr_sts_offset(bus);
+    uint32_t reg_byte_buf = aspeed_i2c_bus_byte_buf_offset(bus);
+    uint32_t value;
+
+    switch (event) {
+    case I2C_START_SEND_ASYNC:
+        value = SHARED_ARRAY_FIELD_EX32(bus->regs, reg_byte_buf, TX_BUF);
+        SHARED_ARRAY_FIELD_DP32(bus->regs, reg_byte_buf, RX_BUF, value << 1);
+
+        ARRAY_FIELD_DP32(bus->regs, I2CD_INTR_STS, SLAVE_ADDR_RX_MATCH, 1);
+        SHARED_ARRAY_FIELD_DP32(bus->regs, reg_intr_sts, RX_DONE, 1);
+
+        aspeed_i2c_set_state(bus, I2CD_STXD);
+
+        break;
+
+    case I2C_FINISH:
+        SHARED_ARRAY_FIELD_DP32(bus->regs, reg_intr_sts, NORMAL_STOP, 1);
+
+        aspeed_i2c_set_state(bus, I2CD_IDLE);
+
+        break;
+
+    default:
+        return -1;
+    }
+
+    aspeed_i2c_bus_raise_interrupt(bus);
+
+    return 0;
+}
+
+static void aspeed_i2c_bus_slave_send_async(I2CSlave *slave, uint8_t data)
+{
+    BusState *qbus = qdev_get_parent_bus(DEVICE(slave));
+    AspeedI2CBus *bus = ASPEED_I2C_BUS(qbus->parent);
+    uint32_t reg_intr_sts = aspeed_i2c_bus_intr_sts_offset(bus);
+    uint32_t reg_byte_buf = aspeed_i2c_bus_byte_buf_offset(bus);
+
+    SHARED_ARRAY_FIELD_DP32(bus->regs, reg_byte_buf, RX_BUF, data);
+    SHARED_ARRAY_FIELD_DP32(bus->regs, reg_intr_sts, RX_DONE, 1);
+
+    aspeed_i2c_bus_raise_interrupt(bus);
+}
+
+static void aspeed_i2c_bus_slave_class_init(ObjectClass *klass, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(klass);
+    I2CSlaveClass *sc = I2C_SLAVE_CLASS(klass);
+
+    dc->desc = "Aspeed I2C Bus Slave";
+
+    sc->event = aspeed_i2c_bus_slave_event;
+    sc->send_async = aspeed_i2c_bus_slave_send_async;
+}
+
+static const TypeInfo aspeed_i2c_bus_slave_info = {
+    .name           = TYPE_ASPEED_I2C_BUS_SLAVE,
+    .parent         = TYPE_I2C_SLAVE,
+    .instance_size  = sizeof(AspeedI2CBusSlave),
+    .class_init     = aspeed_i2c_bus_slave_class_init,
+};
+
 static void aspeed_i2c_bus_reset(DeviceState *dev)
 {
     AspeedI2CBus *s = ASPEED_I2C_BUS(dev);
@@ -1060,6 +1128,8 @@ static void aspeed_i2c_bus_realize(DeviceState *dev, Error **errp)
     sysbus_init_irq(SYS_BUS_DEVICE(dev), &s->irq);
 
     s->bus = i2c_init_bus(dev, name);
+    s->slave = i2c_slave_create_simple(s->bus, TYPE_ASPEED_I2C_BUS_SLAVE,
+                                       0xff);
 
     memory_region_init_io(&s->mr, OBJECT(s), &aspeed_i2c_bus_ops,
                           s, name, aic->reg_size);
@@ -1219,6 +1289,7 @@ static const TypeInfo aspeed_1030_i2c_info = {
 static void aspeed_i2c_register_types(void)
 {
     type_register_static(&aspeed_i2c_bus_info);
+    type_register_static(&aspeed_i2c_bus_slave_info);
     type_register_static(&aspeed_i2c_info);
     type_register_static(&aspeed_2400_i2c_info);
     type_register_static(&aspeed_2500_i2c_info);

include/hw/i2c/aspeed_i2c.h

@@ -223,6 +223,9 @@ struct AspeedI2CBus {
 
     struct AspeedI2CState *controller;
 
+    /* slave mode */
+    I2CSlave *slave;
+
     MemoryRegion mr;
 
     I2CBus *bus;
@@ -249,6 +252,11 @@ struct AspeedI2CState {
     AddressSpace dram_as;
 };
 
+#define TYPE_ASPEED_I2C_BUS_SLAVE "aspeed.i2c.slave"
+OBJECT_DECLARE_SIMPLE_TYPE(AspeedI2CBusSlave, ASPEED_I2C_BUS_SLAVE)
+struct AspeedI2CBusSlave {
+    I2CSlave i2c;
+};
 
 struct AspeedI2CClass {
     SysBusDeviceClass parent_class;