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

[Jorge Ramirez-Ortiz, Foundries]

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

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
>