linux-kernel - Re: [PATCH v2 1/2] i2c: ocores: increase poll timeout to total transfer timeout

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Message-ID: <60744be2-1a22-4056-bf05-22f64fb8b484@lunn.ch>
Date: Thu, 9 Oct 2025 15:20:36 +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 v2 1/2] i2c: ocores: increase poll timeout to total
 transfer timeout

On Thu, Oct 09, 2025 at 11:19:49AM +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.
> 
> The behavior in the regular case is unchanged, spinning for up to 1ms,
> but the open-coded poll loop is replaced with read_poll_timeout_atomic()
> as suggested by Andrew Lunn. In cases where 1ms is not sufficient,
> read_poll_timeout() is used, allowing a total transfer time up to the
> timeout set in struct i2c_adapter (defaulting to 1s, configurable through
> the I2C_TIMEOUT ioctl).

Thanks

Did you test with CONFIG_DEBUG_ATOMIC_SLEEP enabled? I don't think it
is an issue, but the old code could be used in atomic context because
it never slept.

Reviewed-by: Andrew Lunn <andrew@...n.ch>

    Andrew