[PATCH v4 3/4] i2c: stm32: do not set the STOP condition on error

[Alain Volmat]

Current function stm32_i2c_message_xfer is sending a STOP
whatever the result of the transaction is.  This can cause issues
such as making the bus busy since the controller itself is already
sending automatically a STOP when a NACK is generated.

Thanks to Jorge Ramirez-Ortiz for diagnosing and proposing a first
fix for this. [1]

[1] https://lore.kernel.org/u-boot/20220815145211.31342-2-jorge@foundries.io/

Reported-by: Jorge Ramirez-Ortiz, Foundries <jorge at foundries.io>
Signed-off-by: Jorge Ramirez-Ortiz <jorge at foundries.io>
Signed-off-by: Alain Volmat <alain.volmat at foss.st.com>
---
 drivers/i2c/stm32f7_i2c.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/i2c/stm32f7_i2c.c b/drivers/i2c/stm32f7_i2c.c
index 0ec67b5c12..2db7f44d44 100644
--- a/drivers/i2c/stm32f7_i2c.c
+++ b/drivers/i2c/stm32f7_i2c.c
@@ -483,9 +483,9 @@ static int stm32_i2c_message_xfer(struct stm32_i2c_priv *i2c_priv,
 		}
 	}
 
-	/* End of transfer, send stop condition */
-	mask = STM32_I2C_CR2_STOP;
-	setbits_le32(&regs->cr2, mask);
+	/* End of transfer, send stop condition if appropriate */
+	if (!ret && !(status & (STM32_I2C_ISR_NACKF | STM32_I2C_ISR_ERRORS)))
+		setbits_le32(&regs->cr2, STM32_I2C_CR2_STOP);
 
 	return stm32_i2c_check_end_of_message(i2c_priv);
 }
-- 
2.25.1