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

[Jorge Ramirez-Ortiz, Foundries]

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.

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);