[PATCH v6 0/2] i2c: Add dynamic transfer timeout based on message length and frequency

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

The I2C core and most controller drivers use a static 1-second timeout
for all transfers regardless of message length or bus frequency.  This
causes unnecessarily long delays on error paths for short transfers, and
may be tight for very long transfers at low bus frequencies.

This series introduces a generic helper in i2c-core that computes a
transfer-specific timeout and stores it in the standard adap->timeout
field, making the dynamic value visible to the core retry loop in
__i2c_transfer() as well as to the driver's own wait sites.

The helper accepts a safety coefficient and a minimum floor as parameters
so each driver retains control over its own timing policy without those
values becoming public API.

The second patch converts the Qualcomm GENI I2C controller to use this
helper.  The 10x safety margin over the theoretical wire time and the
300ms minimum floor (to budget for clock stretching) remain private to
the qcom-geni driver.

Changes in v6:
- Split into two patches: core helper + driver consumer
- Moved timeout calculation to i2c-core as i2c_update_timeout(), which
  writes directly into adap->timeout so all consumers of that field
  (including the __i2c_transfer() retry loop) benefit automatically
- Driver supplies safety coefficient and minimum floor as parameters,
  keeping I2C_TIMEOUT_SAFETY_COEFFICIENT and I2C_TIMEOUT_MIN_USEC
  internal to i2c-qcom-geni.c
- Compute timeout once per batch in geni_i2c_xfer() using max message
  length, all internal wait sites read adap->timeout directly

Link: https://lore.kernel.org/r/20260715101805.3615166-1-aniket.randive@oss.qualcomm.com

Signed-off-by: Aniket Randive <aniket.randive@oss.qualcomm.com>
---
Aniket Randive (2):
      i2c: core: Add i2c_update_timeout() helper for dynamic transfer timeouts
      i2c: qcom-geni: Add dynamic transfer timeout based on transfer length and frequency

 drivers/i2c/busses/i2c-qcom-geni.c | 37 +++++++++++++++++++++++++++++--------
 drivers/i2c/i2c-core-base.c        | 24 ++++++++++++++++++++++++
 include/linux/i2c.h                |  3 +++
 3 files changed, 56 insertions(+), 8 deletions(-)
---
base-commit: b8809969e1d7a591e0f49dd464a5d04b3cf02ab1
change-id: 20260716-master-f7da57c7529a

Best regards,
--  
Aniket Randive <aniket.randive@oss.qualcomm.com>