[PATCH v3 3/3] i2c: stm32: do not set the STOP condition on error

[Patrick DELAUNAY]

Hi Alain,

On 9/9/22 18:06, Alain Volmat wrote:
> 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);
>   }



Reviewed-by: Patrick Delaunay <patrick.delaunay at foss.st.com>
Tested-by: Patrick Delaunay <patrick.delaunay at foss.st.com> [stm32mp157c-dk2]

No regression detection on ST Microelectonics board.

- No error trace on boot

- I2C probe command is OK

   STM32MP> i2c probe
   Valid chip addresses: 28 33

- And other tests done with the 2 I2C devices STPMIC1 & STUSB1600 are ok:
   regulalor command

   pmic status command

   USB type C connection/deconnection


@Jorge: can you test also for your use-case, thanks


Thanks
Patrick