linux-kernel - Re: [PATCH 2/4] i2c: at91: implement i2c bus recovery

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Date:   Fri, 25 Oct 2019 09:14:00 +0800
From:   Phil Reid <preid@...ctromag.com.au>
To:     Wolfram Sang <wsa@...-dreams.de>, Codrin.Ciubotariu@...rochip.com
Cc:     kamel.bouhara@...tlin.com, linux-arm-kernel@...ts.infradead.org,
        linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org,
        Nicolas.Ferre@...rochip.com, alexandre.belloni@...tlin.com,
        Ludovic.Desroches@...rochip.com, devicetree@...r.kernel.org,
        thomas.petazzoni@...tlin.com
Subject: Re: [PATCH 2/4] i2c: at91: implement i2c bus recovery

On 24/10/2019 23:07, Wolfram Sang wrote:
> 
>> So at the beginning of a new transfer, we should check if SDA (or SCL?)
>> is low and, if it's true, only then we should try recover the bus.
> 
> Yes, this is the proper time to do it. Remember, I2C does not define a
> timeout.
> 

FYI: Just a single poll at the start of the transfer, for it being low, will cause problems with multi-master buses.
Bus recovery should be attempted after a timeout when trying to communicate, even thou i2c doesn't define a timeout.

I'm trying to fix the designware drivers handling of this at the moment.

-- 
Regards
Phil Reid