[PATCH 2/3 v2] i2c: designware: Extend check for mixed slave addresses

[Jean Delvare <jdelvare@suse.de>]

The i2c-designware driver only supports transfers where all messages
use the same slave address. This condition is currently tested in
i2c_dw_xfer_msg(), with 2 limitations:
* The code only checks the address value, not the 10-bit address
  flag, so it could miss an address change.
* For the AMD Navi GPU devices, the driver uses a dedicated function
  instead of i2c_dw_xfer_msg(), so the check is not performed.

Move the check to the common code path, and add the 10-bit address
flag comparison, to catch and report early if a given transfer is not
supported.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
---
Changes since v1:
* Use unlikely() to help the compiler minimize the performance penalty.

 drivers/i2c/busses/i2c-designware-master.c |   28 ++++++++++++++--------------
 1 file changed, 14 insertions(+), 14 deletions(-)

--- linux-6.16.orig/drivers/i2c/busses/i2c-designware-master.c
+++ linux-6.16/drivers/i2c/busses/i2c-designware-master.c
@@ -429,7 +429,6 @@ i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
 	struct i2c_msg *msgs = dev->msgs;
 	u32 intr_mask;
 	int tx_limit, rx_limit;
-	u32 addr = msgs[dev->msg_write_idx].addr;
 	u32 buf_len = dev->tx_buf_len;
 	u8 *buf = dev->tx_buf;
 	bool need_restart = false;
@@ -440,18 +439,6 @@ i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
 	for (; dev->msg_write_idx < dev->msgs_num; dev->msg_write_idx++) {
 		u32 flags = msgs[dev->msg_write_idx].flags;
 
-		/*
-		 * If target address has changed, we need to
-		 * reprogram the target address in the I2C
-		 * adapter when we are done with this transfer.
-		 */
-		if (msgs[dev->msg_write_idx].addr != addr) {
-			dev_err(dev->dev,
-				"%s: invalid target address\n", __func__);
-			dev->msg_err = -EINVAL;
-			break;
-		}
-
 		if (!(dev->status & STATUS_WRITE_IN_PROGRESS)) {
 			/* new i2c_msg */
 			buf = msgs[dev->msg_write_idx].buf;
@@ -806,10 +793,23 @@ static int
 i2c_dw_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
 {
 	struct dw_i2c_dev *dev = i2c_get_adapdata(adap);
-	int ret;
+	int ret, i;
 
 	dev_dbg(dev->dev, "%s: msgs: %d\n", __func__, num);
 
+	/*
+	 * This driver only supports I2C transfers where all the messages
+	 * use the same address.
+	 */
+	for (i = 1; i < num; i++) {
+		if (unlikely(msgs[i].addr != msgs[0].addr ||
+			     (msgs[i].flags & I2C_M_TEN) != (msgs[0].flags & I2C_M_TEN))) {
+			dev_err(dev->dev,
+				"Mixed slave addresses not supported\n");
+			return -EOPNOTSUPP;
+		}
+	}
+
 	pm_runtime_get_sync(dev->dev);
 
 	switch (dev->flags & MODEL_MASK) {

-- 
Jean Delvare
SUSE L3 Support