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

[Mukesh Savaliya <mukesh.savaliya@oss.qualcomm.com>]

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.
> 
> 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....."
>    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
> +
[...]