Re: [PATCH 1/2] i2c: ocores: replace 1ms poll iteration timeout with total transfer timeout

From: Andrew Lunn

Date: Tue Oct 07 2025 - 08:34:28 EST


On Tue, Oct 07, 2025 at 02:09:24PM +0200, Matthias Schiffer wrote:
> When a target makes use of clock stretching, a timeout of 1ms may not be
> enough. One extreme example is the NXP PTN3460 eDP to LVDS bridge, which
> takes ~320ms to send its ACK after a flash command has been
> submitted.
>
> Replace the per-iteration timeout of 1ms with limiting the total
> transfer time to the timeout set in struct i2c_adapter (defaulting to
> 1s, configurable through the I2C_TIMEOUT ioctl). While we're at it, also
> add a cpu_relax() to the busy poll loop.

1s is a long time to spin. Maybe it would be better to keep with the
current spin for 1ms, and then use one of the helpers from iopoll.h to
do a sleeping wait? Say with 10ms sleeps, up to the 1s maximum?

Andrew