[PATCH] i2c: imx_lpi2c: Fix MSR status check issue in STOP

[Ye Li]

Hi Heiko,

On 4/28/2026 5:55 PM, Heiko Schocher wrote:
> Hello Ye Li,
> 
> On 28.04.26 10:53, Ye Li wrote:
>> In bus_i2c_stop, the MSR SDF is checked in a loop after stop command
>> is sent. Meanwhile, some error status in MSR is also checked by
>> imx_lpci2c_check_clear_error. But the imx_lpci2c_check_clear_error
>> will clear the MSR.
>>
>> It causes problem in below situation:
>> In current loop, SDF does not set, but error status is found by
>> imx_lpci2c_check_clear_error (for example, NDF), then NDF will be cleared
>> and result has NDF error. However, because SDF does not set in this loop,
>> it goes not next loop. When SDF is set in next loop,
>> imx_lpci2c_check_clear_error is re-executed, but as the MSR is cleared,
>> the result is 0. Then the stop return 0. But it should return NDF error.
>>
>> Signed-off-by: Ye Li <ye.li at nxp.com>
>> ---
>>   drivers/i2c/imx_lpi2c.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/i2c/imx_lpi2c.c b/drivers/i2c/imx_lpi2c.c
>> index a309fd6f07c..e2b4fd334ec 100644
>> --- a/drivers/i2c/imx_lpi2c.c
>> +++ b/drivers/i2c/imx_lpi2c.c
>> @@ -239,7 +239,6 @@ static int bus_i2c_stop(struct udevice *bus)
>>       start_time = get_timer(0);
>>       while (1) {
>>           status = readl(&regs->msr);
>> -        result = imx_lpci2c_check_clear_error(regs);
> 
> Wouldn;t it be better to evaluate bits in result too, and return
> if error bits found?

I find below commit in history, please take a look. If evaluate bits and 
return, it moves back to previous clock issue.

commit a32effd2838a62a5d1dcc01f613508f1d90b5667
Author: Gao Pan <pandy.gao at nxp.com>
Date:   Sun Jul 8 11:46:41 2018 +0800

     imx: lpi2c: fix clock issue when NACK detected

     For LPI2C IP, NACK is detected by the rising edge of the ninth clock.
     In current uboot driver, once NACK is detected, it will reset and then
     disable LPI2C master. As a result, we can never see the falling edge
     of the ninth clock.

     Signed-off-by: Gao Pan <pandy.gao at nxp.com>
     Signed-off-by: Peng Fan <peng.fan at nxp.com>
     Reviewed-by: Heiko Schocher <hs at denx.de>


Best regards,
Ye Li

> 
>>           /* stop detect flag */
>>           if (status & LPI2C_MSR_SDF_MASK) {
>>               /* clear stop flag */
>> @@ -250,10 +249,13 @@ static int bus_i2c_stop(struct udevice *bus)
>>           if (get_timer(start_time) > LPI2C_NACK_TOUT_MS) {
>>               debug("stop timeout\n");
>> +            result = imx_lpci2c_check_clear_error(regs);
>>               return -ETIMEDOUT;
>>           }
>>       }
>> +    result = imx_lpci2c_check_clear_error(regs);
>> +
>>       return result;
>>   }
>>
> 
> bye,
> Heiko