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

[Alain Volmat]

Hi Jorge

On Sun, Sep 11, 2022 at 08:57:17PM +0200, Jorge Ramirez-Ortiz, Foundries wrote:
> On 09/09/22, Alain Volmat wrote:
> > Hi Patrick
> > 
> > On Fri, Sep 09, 2022 at 02:53:23PM +0200, Patrick DELAUNAY wrote:
> > > Hi Alain
> > > 
> > > 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).
> > > > 
> > > > 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);
> > > >   }
> > > 
> > > 
> > > Boot on DK2 failed with the traces:
> > 
> > Ouch, I am very sorry about that. I think I might have made a mistake
> > during testing / removing debug traces, leading to this mistake ;-(
> > Very sorry about that, thanks a lot Patrick for the test.
> > 
> 
> Just did a quick verification on my end and at least for my use case it is all
> good.
> 
> My use case is enabling SCP03 on the NXP SE05x using the U-boot i2c driver from
> OP-TEE via the trampoline.
> 
> Also, xould you mind also including the fix below in your series Alain? I think
> it is better if you send them all together.

Sure, just added it in my tree and will put the serie v4 in few seconds.
Thanks a lot for the patch.

Alain

> 
> many thanks for steping up for these fixes
> 
> Jorge
> 
> 
> 
> Author: Jorge Ramirez-Ortiz <jorge at foundries.io>
> Date:   3 minutes ago
> 
>     i2c: stm32: fix usage of rise/fall device tree properties
>     
>     These two device tree properties were not being applied.
>     
>     Signed-off-by: Jorge Ramirez-Ortiz <jorge at foundries.io>
> 
> diff --git a/drivers/i2c/stm32f7_i2c.c b/drivers/i2c/stm32f7_i2c.c
> index 505d27afe8..5231055be0 100644
> --- a/drivers/i2c/stm32f7_i2c.c
> +++ b/drivers/i2c/stm32f7_i2c.c
> @@ -910,17 +910,18 @@ static int stm32_of_to_plat(struct udevice *dev)
>  {
>         const struct stm32_i2c_data *data;
>         struct stm32_i2c_priv *i2c_priv = dev_get_priv(dev);
> -   u32 rise_time, fall_time;
>         int ret;
>  
>         data = (const struct stm32_i2c_data *)dev_get_driver_data(dev);
>         if (!data)
>                 return -EINVAL;
>  
> -   rise_time = dev_read_u32_default(dev, "i2c-scl-rising-time-ns",
> + i2c_priv->setup.rise_time = dev_read_u32_default(dev,
> +                                  "i2c-scl-rising-time-ns",
>                                          STM32_I2C_RISE_TIME_DEFAULT);
>  
> -   fall_time = dev_read_u32_default(dev, "i2c-scl-falling-time-ns",
> + i2c_priv->setup.fall_time = dev_read_u32_default(dev,
> +                                 "i2c-scl-falling-time-ns",
>                                          STM32_I2C_FALL_TIME_DEFAULT);
>  
>         i2c_priv->dnf_dt = dev_read_u32_default(dev, "i2c-digital-filter-width-ns", 0);