linux-kernel - Re: [PATCH] i2c: mpc: Use atomic read and fix break condition

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Message-ID: <YbHKsI35uHz9PjwO@ninjato>
Date:   Thu, 9 Dec 2021 10:21:52 +0100
From:   "wsa@...nel.org" <wsa@...nel.org>
To:     Chris Packham <Chris.Packham@...iedtelesis.co.nz>
Cc:     "mbizon@...ebox.fr" <mbizon@...ebox.fr>,
        "linux-i2c@...r.kernel.org" <linux-i2c@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] i2c: mpc: Use atomic read and fix break condition


> we'd hit the 100us timeout in the poll). But I see no evidence of that 
> actually happening (and no idea what arbitration lost means w.r.t i2c).

On a bus with multiple masters, it means the other master has won the
arbitration because the address it wants to talk to contains more 0 bits.

> I don't know that there is a maximum clock stretch time (we certainly 
> know there are misbehaving devices that hold SCL low forever). The SMBUS 
> protocol adds some timeouts but as far as I know i2c says nothing about 
> how long a remote device can hold SCL.

The above is all correct.

Even with the unclear situation about the 100us, I think this should go
to for-current soon, right?



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