From 5065edb417c4dc4a9642da2006d06fda192199a6 Mon Sep 17 00:00:00 2001
From: Etienne Carriere <etienne.carriere@st.com>
Date: Thu, 12 Jun 2025 14:23:03 +0200
Subject: [PATCH] drivers: i2c: stm32: support more than 256 bytes transfer for
 RTIO

Add support for transfer of more than 256 byte in STM32 v1 and v2
RTIO drivers.

Signed-off-by: Etienne Carriere <etienne.carriere@st.com>
---
 drivers/i2c/i2c_ll_stm32.h         |  4 ++--
 drivers/i2c/i2c_ll_stm32_v1_rtio.c |  6 -----
 drivers/i2c/i2c_ll_stm32_v2_rtio.c | 35 ++++++++++++++++++------------
 3 files changed, 23 insertions(+), 22 deletions(-)

diff --git a/drivers/i2c/i2c_ll_stm32.h b/drivers/i2c/i2c_ll_stm32.h
index b3ca4a5e725..01f9115a5d2 100644
--- a/drivers/i2c/i2c_ll_stm32.h
+++ b/drivers/i2c/i2c_ll_stm32.h
@@ -73,10 +73,10 @@ struct i2c_stm32_data {
 	struct i2c_rtio *ctx;
 	uint32_t dev_config;
 	uint8_t *xfer_buf;
-	uint8_t xfer_len;
+	size_t xfer_len;
 	uint8_t xfer_flags;
 #ifdef CONFIG_I2C_STM32_V1
-	uint8_t msg_len;
+	size_t msg_len;
 	uint8_t is_restart;
 	uint16_t slave_address;
 #endif /* CONFIG_I2C_STM32_V1 */
diff --git a/drivers/i2c/i2c_ll_stm32_v1_rtio.c b/drivers/i2c/i2c_ll_stm32_v1_rtio.c
index 7e8ef89039a..3c0728d79d6 100644
--- a/drivers/i2c/i2c_ll_stm32_v1_rtio.c
+++ b/drivers/i2c/i2c_ll_stm32_v1_rtio.c
@@ -333,12 +333,6 @@ int i2c_stm32_msg_start(const struct device *dev, uint8_t flags,
 	data->is_restart = 0;
 	data->slave_address = i2c_addr;
 
-	/* TODO deal with larger than 255 byte transfers correctly */
-	if (buf_len > UINT8_MAX) {
-		/* TODO LL_I2C_EnableReloadMode(i2c); */
-		return -EINVAL;
-	}
-
 	LL_I2C_Enable(i2c);
 
 	LL_I2C_DisableBitPOS(i2c);
diff --git a/drivers/i2c/i2c_ll_stm32_v2_rtio.c b/drivers/i2c/i2c_ll_stm32_v2_rtio.c
index c0f5697f9c3..519066afad7 100644
--- a/drivers/i2c/i2c_ll_stm32_v2_rtio.c
+++ b/drivers/i2c/i2c_ll_stm32_v2_rtio.c
@@ -101,22 +101,29 @@ void i2c_stm32_event(const struct device *dev)
 		LL_I2C_ClearFlag_STOP(i2c);
 		LL_I2C_DisableReloadMode(i2c);
 		i2c_stm32_master_mode_end(dev);
+
+		if (i2c_rtio_complete(ctx, ret)) {
+			i2c_stm32_start(dev);
+			return;
+		}
 	}
 
-	/* TODO handle the reload separately from complete */
-	/* Transfer Complete or Transfer Complete Reload */
 	if (LL_I2C_IsActiveFlag_TC(i2c) ||
 	    LL_I2C_IsActiveFlag_TCR(i2c)) {
+
 		/* Issue stop condition if necessary */
-		/* TODO look at current sqe flags */
 		if ((data->xfer_flags & I2C_MSG_STOP) != 0) {
-			LL_I2C_GenerateStopCondition(i2c);
+			if (data->xfer_len == 0) {
+				LL_I2C_GenerateStopCondition(i2c);
+			} else {
+				LL_I2C_SetTransferSize(i2c, MIN(data->xfer_len, UINT8_MAX));
+			}
 		} else {
 			i2c_stm32_disable_transfer_interrupts(dev);
-		}
 
-		if ((data->xfer_len == 0) && i2c_rtio_complete(ctx, ret)) {
-			i2c_stm32_start(dev);
+			if ((data->xfer_len == 0) && i2c_rtio_complete(ctx, ret)) {
+				i2c_stm32_start(dev);
+			}
 		}
 	}
 }
@@ -162,12 +169,6 @@ int i2c_stm32_msg_start(const struct device *dev, uint8_t flags,
 		transfer = LL_I2C_REQUEST_WRITE;
 	}
 
-	/* TODO deal with larger than 255 byte transfers correctly */
-	if (buf_len > UINT8_MAX) {
-		/* TODO LL_I2C_EnableReloadMode(i2c); */
-		return -EINVAL;
-	}
-
 	if ((I2C_MSG_ADDR_10_BITS & flags) != 0) {
 		LL_I2C_SetMasterAddressingMode(i2c,
 				LL_I2C_ADDRESSING_MODE_10BIT);
@@ -178,9 +179,15 @@ int i2c_stm32_msg_start(const struct device *dev, uint8_t flags,
 		LL_I2C_SetSlaveAddr(i2c, (uint32_t) i2c_addr << 1);
 	}
 
+	if (buf_len > UINT8_MAX) {
+		LL_I2C_EnableReloadMode(i2c);
+	} else {
+		LL_I2C_DisableReloadMode(i2c);
+	}
+
 	LL_I2C_DisableAutoEndMode(i2c);
 	LL_I2C_SetTransferRequest(i2c, transfer);
-	LL_I2C_SetTransferSize(i2c, buf_len);
+	LL_I2C_SetTransferSize(i2c, MIN(buf_len, UINT8_MAX));
 
 	LL_I2C_Enable(i2c);