i2c: designware: slave should do WRITE_REQUESTED before WRITE_RECEIVED

Sometimes we would get the following flow when doing an i2cset:

0x1 STATUS SLAVE_ACTIVITY=0x1 : RAW_INTR_STAT=0x514 : INTR_STAT=0x4
I2C_SLAVE_WRITE_RECEIVED
0x1 STATUS SLAVE_ACTIVITY=0x0 : RAW_INTR_STAT=0x714 : INTR_STAT=0x204
I2C_SLAVE_WRITE_REQUESTED
I2C_SLAVE_WRITE_RECEIVED

Documentation/i2c/slave-interface.rst says that I2C_SLAVE_WRITE_REQUESTED,
which is mandatory, should be sent while the data did not arrive yet. It
means in a write-request I2C_SLAVE_WRITE_REQUESTED should be reported
before any I2C_SLAVE_WRITE_RECEIVED.

By the way, I2C_SLAVE_STOP didn't be reported in the above case because
DW_IC_INTR_STAT was not 0x200.

dev->status can be used to record the current state, especially Designware
I2C controller has no interrupts to identify a write-request. This patch
makes not only I2C_SLAVE_WRITE_REQUESTED been reported first when
IC_INTR_RX_FULL is rising and dev->status isn't STATUS_WRITE_IN_PROGRESS
but also I2C_SLAVE_STOP been reported when a STOP condition is received.
Signed-off-by: Michael Wu <michael.wu@vatics.com>
Acked-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/busses/i2c-designware-slave.c

@@ -172,26 +172,25 @@ static int i2c_dw_irq_handler_slave(struct dw_i2c_dev *dev)
 		"%#x STATUS SLAVE_ACTIVITY=%#x : RAW_INTR_STAT=%#x : INTR_STAT=%#x\n",
 		enabled, slave_activity, raw_stat, stat);
 
-	if ((stat & DW_IC_INTR_RX_FULL) && (stat & DW_IC_INTR_STOP_DET))
-		i2c_slave_event(dev->slave, I2C_SLAVE_WRITE_REQUESTED, &val);
+	if (stat & DW_IC_INTR_RX_FULL) {
+		if (dev->status != STATUS_WRITE_IN_PROGRESS) {
+			dev->status = STATUS_WRITE_IN_PROGRESS;
+			i2c_slave_event(dev->slave, I2C_SLAVE_WRITE_REQUESTED,
+					&val);
+		}
+
+		regmap_read(dev->map, DW_IC_DATA_CMD, &tmp);
+		val = tmp;
+		if (!i2c_slave_event(dev->slave, I2C_SLAVE_WRITE_RECEIVED,
+				     &val))
+			dev_vdbg(dev->dev, "Byte %X acked!", val);
+	}
 
 	if (stat & DW_IC_INTR_RD_REQ) {
 		if (slave_activity) {
-			if (stat & DW_IC_INTR_RX_FULL) {
-				regmap_read(dev->map, DW_IC_DATA_CMD, &tmp);
-				val = tmp;
-
-				if (!i2c_slave_event(dev->slave,
-						     I2C_SLAVE_WRITE_RECEIVED,
-						     &val)) {
-					dev_vdbg(dev->dev, "Byte %X acked!",
-						 val);
-				}
-				regmap_read(dev->map, DW_IC_CLR_RD_REQ, &tmp);
-			} else {
-				regmap_read(dev->map, DW_IC_CLR_RD_REQ, &tmp);
-				regmap_read(dev->map, DW_IC_CLR_RX_UNDER, &tmp);
-			}
+			regmap_read(dev->map, DW_IC_CLR_RD_REQ, &tmp);
+
+			dev->status = STATUS_READ_IN_PROGRESS;
 			if (!i2c_slave_event(dev->slave,
 					     I2C_SLAVE_READ_REQUESTED,
 					     &val))
@@ -203,18 +202,10 @@ static int i2c_dw_irq_handler_slave(struct dw_i2c_dev *dev)
 		if (!i2c_slave_event(dev->slave, I2C_SLAVE_READ_PROCESSED,
 				     &val))
 			regmap_read(dev->map, DW_IC_CLR_RX_DONE, &tmp);
-
-		i2c_slave_event(dev->slave, I2C_SLAVE_STOP, &val);
-		return 1;
 	}
 
-	if (stat & DW_IC_INTR_RX_FULL) {
-		regmap_read(dev->map, DW_IC_DATA_CMD, &tmp);
-		val = tmp;
-		if (!i2c_slave_event(dev->slave, I2C_SLAVE_WRITE_RECEIVED,
-				     &val))
-			dev_vdbg(dev->dev, "Byte %X acked!", val);
-	} else {
+	if (stat & DW_IC_INTR_STOP_DET) {
+		dev->status = STATUS_IDLE;
 		i2c_slave_event(dev->slave, I2C_SLAVE_STOP, &val);
 	}