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

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Message-ID: <7dbefacc-3ce0-47ea-b521-102320f49420@lunn.ch>
Date: Tue, 7 Oct 2025 14:34:25 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Matthias Schiffer <matthias.schiffer@...tq-group.com>
Cc: Peter Korsgaard <peter@...sgaard.com>,
	Andi Shyti <andi.shyti@...nel.org>, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux@...tq-group.com
Subject: Re: [PATCH 1/2] i2c: ocores: replace 1ms poll iteration timeout with
 total transfer timeout

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