[PATCH v2 3/3] i2c: stm32: only send a STOP upon transfer completion

[Patrick DELAUNAY]

Hi,

On 9/9/22 10:43, Heiko Schocher wrote:
> Hello Jorge,
>
> On 09.09.22 10:30, Jorge Ramirez-Ortiz, Foundries wrote:
>> On 08/09/22, Patrick DELAUNAY wrote:
>>> Hi,
>>>
>>> On 9/8/22 12:59, 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.  This can
>>>> be especially seen when the processing get slower (ex: enabling lots
>>>> of debug messages), ending up send 2 STOP (one automatically by the
>>>> controller and a 2nd one at the end of the stm32_i2c_message_xfer
>>>> function).
>>>>
>> Cmon no need to thank me, that is kind of excessive :)
>> Just the sign-off or codevelop tags for reference
>>
>>
>> if you can wait before merging I will test the series before monday
> I would love to see a test before we merge this.
>
> @Patrick: feel free to merge it through stm32 repo.


Ok, I will take this serie in my next pull request for stm32


>
> Thanks!
>
> bye,
> Heiko


By Patrick


>> thanks
>> Jorge
>>
>>>> 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 | 8 ++++----
>>>>    1 file changed, 4 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/i2c/stm32f7_i2c.c b/drivers/i2c/stm32f7_i2c.c
>>>> index 0ec67b5c12..8803979d3e 100644
>>>> --- a/drivers/i2c/stm32f7_i2c.c
>>>> +++ b/drivers/i2c/stm32f7_i2c.c
>>>> @@ -477,16 +477,16 @@ static int stm32_i2c_message_xfer(struct stm32_i2c_priv *i2c_priv,
>>>>    			if (ret)
>>>>    				break;
>>>> +			/* End of transfer, send stop condition */
>>>> +			mask = STM32_I2C_CR2_STOP;
>>>> +			setbits_le32(&regs->cr2, mask);
>>>> +
>>>>    			if (!stop)
>>>>    				/* Message sent, new message has to be sent */
>>>>    				return 0;
>>>>    		}
>>>>    	}
>>>> -	/* End of transfer, send stop condition */
>>>> -	mask = STM32_I2C_CR2_STOP;
>>>> -	setbits_le32(&regs->cr2, mask);
>>>> -
>>>>    	return stm32_i2c_check_end_of_message(i2c_priv);
>>>>    }
>>>
>>> Reviewed-by: Patrick Delaunay <patrick.delaunay at foss.st.com>
>>>
>>> Thanks
>>> Patrick
>>>