From: Wolfram Sang <wsa@the-dreams.de>
To: Phil Reid <preid@electromag.com.au>
Cc: kamel.bouhara@bootlin.com, alexandre.belloni@bootlin.com,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
Ludovic.Desroches@microchip.com, linux-i2c@vger.kernel.org,
thomas.petazzoni@bootlin.com, Codrin.Ciubotariu@microchip.com,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 2/4] i2c: at91: implement i2c bus recovery
Date: Tue, 25 Aug 2020 15:28:46 +0200 [thread overview]
Message-ID: <20200825132846.GA1753@kunai> (raw)
In-Reply-To: <65d83bb0-9a0c-c6e2-1c58-cb421c69816c@electromag.com.au>
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Hi Phil,
yes, this thread is old but a similar issue came up again...
On Fri, Oct 25, 2019 at 09:14:00AM +0800, Phil Reid 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.
I wonder what you ended up with? You are right, a single poll is not
enough. It only might be if one applies the new "single-master" binding
for a given bus. If that is not present, my best idea so far is to poll
SDA for the time defined in adapter->timeout and if it is all low, then
initiate a recovery.
All the best,
Wolfram
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next prev parent reply other threads:[~2020-08-25 13:30 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-02 14:46 [PATCH 0/4] i2c bus recovery for Microchip SoCs Kamel Bouhara
2019-10-02 14:46 ` [PATCH 1/4] dt-bindings: i2c: at91: document optional bus recovery properties Kamel Bouhara
2019-10-02 14:46 ` [PATCH 2/4] i2c: at91: implement i2c bus recovery Kamel Bouhara
2019-10-04 9:35 ` Claudiu.Beznea
2019-10-04 20:39 ` Uwe Kleine-König
2019-10-07 10:17 ` Claudiu.Beznea
2019-10-09 13:55 ` Ludovic Desroches
2019-10-09 14:01 ` Alexandre Belloni
2019-10-10 6:54 ` Ludovic Desroches
2019-10-24 12:29 ` Kamel Bouhara
2019-10-25 7:04 ` Ludovic.Desroches
2019-10-21 20:20 ` Wolfram Sang
2019-10-22 7:59 ` Kamel Bouhara
2019-10-24 14:08 ` Codrin.Ciubotariu
2019-10-24 15:07 ` Wolfram Sang
2019-10-25 1:14 ` Phil Reid
2020-08-25 13:28 ` Wolfram Sang [this message]
2020-08-25 23:44 ` Phil Reid
2019-10-02 14:46 ` [PATCH 3/4] ARM: at91/dt: sama5d3: add i2c gpio pinctrl Kamel Bouhara
2019-10-02 14:46 ` [PATCH 4/4] ARM: at91/dt: sama5d4: " Kamel Bouhara
2019-10-15 19:10 ` [PATCH 0/4] i2c bus recovery for Microchip SoCs Rob Herring
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