drivers: i2c: sam0: Continue write/read if next message allows it

Update sam0 i2c driver to directly send/receive next message if it is
in the same direction and the current message has no stop or restart
flags. Seems like in some drivers this is the expected behaviour.

Fixes #36857

Signed-off-by: Christoffer Zakrisson <rustypig91@gmail.com>

Author: rustypig91

drivers/i2c/i2c_sam0.c

@@ -52,6 +52,8 @@ struct i2c_sam0_msg {
 struct i2c_sam0_dev_data {
 	struct k_sem sem;
 	struct i2c_sam0_msg msg;
+	struct i2c_msg *msgs;
+	uint8_t num_msgs;
 };
 
 #define DEV_NAME(dev) ((dev)->name)
@@ -137,6 +139,18 @@ static void i2c_sam0_isr(const struct device *dev)
 		return;
 	}
 
+	/*
+	 * Directly send/receive next message if it is in the same direction and
+	 * the current message has no stop flag and the next message has no
+	 * restart flag.
+	 */
+	const bool continue_next = (data->msg.size == 1) && (data->num_msgs > 1) &&
+				   ((data->msgs[0].flags & I2C_MSG_RW_MASK) ==
+				    (data->msgs[1].flags & I2C_MSG_RW_MASK)) &&
+				   !(data->msgs[0].flags & I2C_MSG_STOP) &&
+				   !(data->msgs[1].flags & I2C_MSG_RESTART) &&
+				   ((status & (SERCOM_I2CM_INTFLAG_MB | SERCOM_I2CM_INTFLAG_SB)));
+
 	if (status & SERCOM_I2CM_INTFLAG_MB) {
 		if (!data->msg.size) {
 			i2c->INTENCLR.reg = SERCOM_I2CM_INTENCLR_MASK;
@@ -147,12 +161,8 @@ static void i2c_sam0_isr(const struct device *dev)
 		i2c->DATA.reg = *data->msg.buffer;
 		data->msg.buffer++;
 		data->msg.size--;
-
-		return;
-	}
-
-	if (status & SERCOM_I2CM_INTFLAG_SB) {
-		if (data->msg.size == 1) {
+	} else if (status & SERCOM_I2CM_INTFLAG_SB) {
+		if (!continue_next) {
 			/*
 			 * If this is the last byte, then prepare for an auto
 			 * NACK before doing the actual read.  This does not
@@ -165,12 +175,20 @@ static void i2c_sam0_isr(const struct device *dev)
 		data->msg.buffer++;
 		data->msg.size--;
 
-		if (!data->msg.size) {
+		if (!continue_next) {
 			i2c->INTENCLR.reg = SERCOM_I2CM_INTENCLR_MASK;
 			k_sem_give(&data->sem);
 			return;
 		}
-		return;
+	}
+
+	if (continue_next) {
+		data->msgs++;
+		data->num_msgs--;
+
+		data->msg.buffer = data->msgs->buf;
+		data->msg.size = data->msgs->len;
+		data->msg.status = 0;
 	}
 }
 
@@ -373,10 +391,12 @@ static int i2c_sam0_transfer(const struct device *dev, struct i2c_msg *msgs,
 	if (!num_msgs) {
 		return 0;
 	}
+	data->num_msgs = num_msgs;
+	data->msgs = msgs;
 
-	for (; num_msgs > 0;) {
-		if (!msgs->len) {
-			if ((msgs->flags & I2C_MSG_RW_MASK) == I2C_MSG_READ) {
+	for (; data->num_msgs > 0;) {
+		if (!data->msgs->len) {
+			if ((data->msgs->flags & I2C_MSG_RW_MASK) == I2C_MSG_READ) {
 				return -EINVAL;
 			}
 		}
@@ -392,20 +412,20 @@ static int i2c_sam0_transfer(const struct device *dev, struct i2c_msg *msgs,
 				  SERCOM_I2CM_STATUS_BUSERR;
 		wait_synchronization(i2c);
 
-		data->msg.buffer = msgs->buf;
-		data->msg.size = msgs->len;
+		data->msg.buffer = data->msgs->buf;
+		data->msg.size = data->msgs->len;
 		data->msg.status = 0;
 
 		addr_reg = addr << 1U;
-		if ((msgs->flags & I2C_MSG_RW_MASK) == I2C_MSG_READ) {
+		if ((data->msgs->flags & I2C_MSG_RW_MASK) == I2C_MSG_READ) {
 			addr_reg |= 1U;
 
 			/* Set to auto ACK */
 			i2c->CTRLB.bit.ACKACT = 0;
 			wait_synchronization(i2c);
 		}
 
-		if (msgs->flags & I2C_MSG_ADDR_10_BITS) {
+		if (data->msgs->flags & I2C_MSG_ADDR_10_BITS) {
 #ifdef SERCOM_I2CM_ADDR_TENBITEN
 			addr_reg |= SERCOM_I2CM_ADDR_TENBITEN;
 #else
@@ -432,7 +452,7 @@ static int i2c_sam0_transfer(const struct device *dev, struct i2c_msg *msgs,
 		i2c->INTENSET.reg = SERCOM_I2CM_INTENSET_ERROR;
 #endif
 
-		if ((msgs->flags & I2C_MSG_RW_MASK) == I2C_MSG_READ) {
+		if ((data->msgs->flags & I2C_MSG_RW_MASK) == I2C_MSG_READ) {
 			/*
 			 * Always set MB even when reading, since that's how
 			 * some errors are indicated.
@@ -472,9 +492,9 @@ static int i2c_sam0_transfer(const struct device *dev, struct i2c_msg *msgs,
 			return -EIO;
 		}
 
-		if (msgs->flags & I2C_MSG_STOP) {
+		if (data->msgs->flags & I2C_MSG_STOP) {
 			i2c->CTRLB.bit.CMD = 3;
-		} else if ((msgs->flags & I2C_MSG_RESTART) && num_msgs > 1) {
+		} else if ((data->msgs->flags & I2C_MSG_RESTART) && data->num_msgs > 1) {
 			/*
 			 * No action, since we do this automatically if we
 			 * don't send an explicit stop
@@ -487,8 +507,8 @@ static int i2c_sam0_transfer(const struct device *dev, struct i2c_msg *msgs,
 			i2c->CTRLB.bit.CMD = 3;
 		}
 
-		num_msgs--;
-		msgs++;
+		data->num_msgs--;
+		data->msgs++;
 	}
 
 	return 0;