Re: [PATCH V4] i2c: qcom-geni: Add dynamic transfer timeout based on transfer length and frequency

[Aniket RANDIVE <aniket.randive@oss.qualcomm.com>]

On 7/15/2026 9:36 AM, Mukesh Savaliya wrote:
> Hi Aniket, Thanks for addressing previous comments.
> 
> On 7/10/2026 9:40 PM, Aniket Randive wrote:
>> The driver uses a static XFER_TIMEOUT of HZ (1 second) for all transfers
>> regardless of message length or bus frequency, causing unnecessary
>> delays on error paths.
>>
>> Compute the timeout dynamically from message length and bus frequency
>> with a 10x safety margin over the theoretical wire time. Add a 300ms
>> floor to budget for I2C clock stretching, where a slave may hold SCL
>> low indefinitely during internal processing. This detects real hangs
> not only internal processing but it may go bad holding SCL low 
> indefinitely.
>> 3x faster than the old 1s static timeout.
> Meaning, in such case/scenario, don't need to wait till fixes timeout.
> I guess, 3x faster is relative to the 1 sec, but for larger data and 
> slower frequency it may not be 3x. Hence, correct it accordingly.

I will update the commit message in next patch.
Thanks,
Aniket

>>
>> For GPI multi-descriptor transfers, use the maximum message length across
>> all queued messages as the per-completion timeout.
>>
>> Signed-off-by: Aniket Randive <aniket.randive@oss.qualcomm.com>
>> ---
>>
>> Changes in v4:
>>   - As per konrad suggestion used mult_frac() for bit_usec to avoid 
>> intermediate
> Do not keep space before starting, directly start with "- As per....."

Ok. I will take care of this in next patch.
Thanks,
Aniket

>>    overflow on 32-bit targets.
>>   - Updated the commit message and added a driver comment explaining the
>>     rationale for the 0.3-second minimum timeout floor value.
>>
>>   drivers/i2c/busses/i2c-qcom-geni.c | 46 +++++++++++++++++++++++-------
>>   1 file changed, 36 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/ 
>> i2c-qcom-geni.c
>> index 96dbf04138be..c5c3adc8ec77 100644
>> --- a/drivers/i2c/busses/i2c-qcom-geni.c
>> +++ b/drivers/i2c/busses/i2c-qcom-geni.c
>> @@ -74,9 +74,13 @@ enum geni_i2c_err_code {
>>   #define PACKING_BYTES_PW    4
>>   #define ABORT_TIMEOUT        HZ
>> -#define XFER_TIMEOUT        HZ
>>   #define RST_TIMEOUT        HZ
>> +/* 9 bits per byte (8 data + 1 ACK), 10x safety margin */
>> +#define I2C_TIMEOUT_SAFETY_COEFFICIENT    10
> Add a line space to make it look clean
>> +/* 300ms floor: budget for clock stretching; slave may hold SCL low 
>> indefinitely */
> Already explained in commit log, can remove second part.
> 
>> +#define I2C_TIMEOUT_MIN_USEC        300000
>> +
> [...]