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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Proofpoint-ORIG-GUID: JfLMVA9r07sNUwupeekRlTMSJ8M4k-Jn X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzIyMDA0NyBTYWx0ZWRfXyOdxUYazOgP2 d+adICkWGRlozZ3oHRtLBtSzcGoid0YoND/hx4Iy/KxM6H9c38a4iF2rhyZDZSqOEXKfgyMTtBr kfn8c6CMMpO/5xxoB0RYWm7K5qaGTU8xN/fRFaXdwc4N1ZT7DyaFSOf3dZbi4S/vOOj7kQF/MFm SVt784u3qO79eyE5uK60pCfLUlFX9vijJX9KcKtVjDXHLnveTPkPtDvcfppOqc8LofMgvPtt+nq xwmVT9e051nQx/3FBCkQ8D5Ssr+WoNLvFZuCFGiswnTGG7pYlyIJw2qb+kzm7DDxylwUvYHzEKT gFbsBHVuf0NlMe+M+BGqO37X37G5AwXWIZ6sgX5vCEmeSF7JNwu65IEeF7S7e5foiJyexWdEeuu Yx1hmGPPMZsD83B7eqTCwE0eiVJ5G9X/gtp52VjFyqKei5daSltGDnhj2XLhz9Fws6+lDyvsV+N SKM5HXC0EXLX3Htq9/A== X-Proofpoint-GUID: JfLMVA9r07sNUwupeekRlTMSJ8M4k-Jn X-Proofpoint-Spam-Info: AW1haW4tMjYwNzIyMDA0NyBTYWx0ZWRfX369gSuCDYaBR GhZX/uEG+QszCWnsGDlLcSwBLbSILIMZujPQIv1p1LmT+TuZFZCB8/3sQqlpoGvww+JgUkzxbGi +Wrlgo3S6CAERMpU0Ghmekl2masr0a8= X-Authority-Analysis: v=2.4 cv=QK1YgALL c=1 sm=1 tr=0 ts=6a605458 cx=c_pps a=JL+w9abYAAE89/QcEU+0QA==:117 a=fChuTYTh2wq5r3m49p7fHw==:17 a=IkcTkHD0fZMA:10 a=RAioF0-LDSMA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=yOCtJkima9RkubShWh1s:22 a=EUspDBNiAAAA:8 a=W_snkT02l9C0IohT3WkA:9 a=QEXdDO2ut3YA:10 a=324X-CrmTo6CU4MGRt3R:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-22_02,2026-07-21_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 spamscore=0 phishscore=0 impostorscore=0 bulkscore=0 suspectscore=0 clxscore=1015 adultscore=0 lowpriorityscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607220047 On 7/20/2026 5:11 PM, Aniket Randive wrote: > The transfer timeout for an I2C controller should reflect the actual > message length and bus frequency rather than a static 1-second value. > A static timeout causes unnecessary delays on error paths for short > messages, and may be insufficient for very long transfers. > in short write as should be relative to the bus speed and data length instead of any hard coded values. > Add i2c_update_timeout() to i2c-core which computes a transfer-specific > timeout and stores it directly in the standard adap->timeout field. The > formula accounts for 9 bits per byte (8 data + 1 ACK) at the configured > bus frequency. The caller supplies a safety multiplier and a minimum > floor so that each driver retains full control over its timing policy > without those values becoming public API. > > Storing the result in adap->timeout makes it visible to all consumers of > that field, including the arbitration-loss retry loop in __i2c_transfer(). > > Signed-off-by: Aniket Randive > --- > drivers/i2c/i2c-core-base.c | 24 ++++++++++++++++++++++++ > include/linux/i2c.h | 3 +++ > 2 files changed, 27 insertions(+) > > diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c > index 3ec04787a737..3280652e20d8 100644 > --- a/drivers/i2c/i2c-core-base.c > +++ b/drivers/i2c/i2c-core-base.c > @@ -29,6 +29,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -2000,6 +2001,29 @@ void i2c_parse_fw_timings(struct device *dev, struct i2c_timings *t, bool use_de > } > EXPORT_SYMBOL_GPL(i2c_parse_fw_timings); > can i2c-core-base.c calculate within and store into adap->timeout ? Current adap->timeout = HZ can be removed if we add coefficient and safety factor default ? Any other thoughts ? > +/** > + * i2c_update_timeout - compute and set a dynamic transfer timeout on an adapter > + * @adap: the i2c_adapter whose timeout field will be updated > + * @bus_freq_hz: I2C bus clock frequency in Hz > + * @len: transfer length in bytes > + * @safety_coeff: multiplier applied over the theoretical wire time > + * @min_usec: minimum timeout floor in microseconds > + * > + * Computes a transfer-specific timeout from the message length and bus > + * frequency, applies a safety multiplier and a minimum floor, then stores > + * the result in adap->timeout (in jiffies). The caller supplies the policy > + * constants so they remain internal to the driver. > + */ > +void i2c_update_timeout(struct i2c_adapter *adap, u32 bus_freq_hz, > + size_t len, unsigned int safety_coeff, > + unsigned int min_usec) > +{ > + u64 bit_usec = mul_u64_u32_div(len * 9, USEC_PER_SEC, bus_freq_hz); > + > + adap->timeout = usecs_to_jiffies(bit_usec * safety_coeff + min_usec); > +} > +EXPORT_SYMBOL_GPL(i2c_update_timeout); why is this exported ? you have alrady added in i2c.h ? > + > /* ------------------------------------------------------------------------- */ > > int i2c_for_each_dev(void *data, int (*fn)(struct device *dev, void *data)) > diff --git a/include/linux/i2c.h b/include/linux/i2c.h > index 14ab4d3055af..b52974eb7e58 100644 > --- a/include/linux/i2c.h > +++ b/include/linux/i2c.h > @@ -912,6 +912,9 @@ void i2c_put_adapter(struct i2c_adapter *adap); > unsigned int i2c_adapter_depth(struct i2c_adapter *adapter); > > void i2c_parse_fw_timings(struct device *dev, struct i2c_timings *t, bool use_defaults); > +void i2c_update_timeout(struct i2c_adapter *adap, u32 bus_freq_hz, > + size_t len, unsigned int safety_coeff, > + unsigned int min_usec); > > /* Return the functionality mask */ > static inline u32 i2c_get_functionality(struct i2c_adapter *adap) >