hw/i2c: add asynchronous send

Add an asynchronous version of i2c_send() that requires the slave to
explicitly acknowledge on the bus with i2c_ack().

The current master must use the new i2c_start_send_async() to indicate
that it wants to do an asynchronous transfer. This allows the i2c core
to check if the target slave supports this or not. This approach relies
on adding a new enum i2c_event member, which is why a bunch of other
devices needs changes in their event handling switches.

Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
Message-Id: <20220601210831.67259-5-its@irrelevant.dk>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-Id: <20220630045133.32251-6-me@pjd.dev>
Signed-off-by: Cédric Le Goater <clg@kaod.org>

3 files changed, 41 insertions, 1 deletions

diff --git a/hw/i2c/core.c b/hw/i2c/core.c
index 145dce6078..d4ba8146bf 100644
--- a/hw/i2c/core.c
+++ b/hw/i2c/core.c
@@ -161,7 +161,8 @@ static int i2c_do_start_transfer(I2CBus *bus, uint8_t address,
            start condition.  */
 
         if (sc->event) {
-            trace_i2c_event("start", s->address);
+            trace_i2c_event(event == I2C_START_SEND ? "start" : "start_async",
+                            s->address);
             rv = sc->event(s, event);
             if (rv && !bus->broadcast) {
                 if (bus_scanned) {
@@ -212,6 +213,11 @@ int i2c_start_send(I2CBus *bus, uint8_t address)
     return i2c_do_start_transfer(bus, address, I2C_START_SEND);
 }
 
+int i2c_start_send_async(I2CBus *bus, uint8_t address)
+{
+    return i2c_do_start_transfer(bus, address, I2C_START_SEND_ASYNC);
+}
+
 void i2c_end_transfer(I2CBus *bus)
 {
     I2CSlaveClass *sc;
@@ -261,6 +267,23 @@ int i2c_send(I2CBus *bus, uint8_t data)
     return ret ? -1 : 0;
 }
 
+int i2c_send_async(I2CBus *bus, uint8_t data)
+{
+    I2CNode *node = QLIST_FIRST(&bus->current_devs);
+    I2CSlave *slave = node->elt;
+    I2CSlaveClass *sc = I2C_SLAVE_GET_CLASS(slave);
+
+    if (!sc->send_async) {
+        return -1;
+    }
+
+    trace_i2c_send_async(slave->address, data);
+
+    sc->send_async(slave, data);
+
+    return 0;
+}
+
 uint8_t i2c_recv(I2CBus *bus)
 {
     uint8_t data = 0xff;
@@ -297,6 +320,17 @@ void i2c_nack(I2CBus *bus)
     }
 }
 
+void i2c_ack(I2CBus *bus)
+{
+    if (!bus->bh) {
+        return;
+    }
+
+    trace_i2c_ack();
+
+    qemu_bh_schedule(bus->bh);
+}
+
 static int i2c_slave_post_load(void *opaque, int version_id)
 {
     I2CSlave *dev = opaque;
diff --git a/hw/i2c/smbus_slave.c b/hw/i2c/smbus_slave.c
index 5d10e27664..feb3ec6333 100644
--- a/hw/i2c/smbus_slave.c
+++ b/hw/i2c/smbus_slave.c
@@ -143,6 +143,10 @@ static int smbus_i2c_event(I2CSlave *s, enum i2c_event event)
             dev->mode = SMBUS_CONFUSED;
             break;
         }
+        break;
+
+    default:
+        return -1;
     }
 
     return 0;
diff --git a/hw/i2c/trace-events b/hw/i2c/trace-events
index 209275ed2d..af181d43ee 100644
--- a/hw/i2c/trace-events
+++ b/hw/i2c/trace-events
@@ -4,7 +4,9 @@
 
 i2c_event(const char *event, uint8_t address) "%s(addr:0x%02x)"
 i2c_send(uint8_t address, uint8_t data) "send(addr:0x%02x) data:0x%02x"
+i2c_send_async(uint8_t address, uint8_t data) "send_async(addr:0x%02x) data:0x%02x"
 i2c_recv(uint8_t address, uint8_t data) "recv(addr:0x%02x) data:0x%02x"
+i2c_ack(void) ""
 
 # aspeed_i2c.c