Re: [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-jo...@foundries.io/

Reported-by: Jorge Ramirez-Ortiz, Foundries <jo...@foundries.io>
Signed-off-by: Jorge Ramirez-Ortiz <jo...@foundries.io>
Signed-off-by: Alain Volmat <alain.vol...@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.delau...@foss.st.com>
Tested-by: Patrick Delaunay <patrick.delau...@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