From: Phil Reid <preid@electromag.com.au>
To: Wolfram Sang <wsa@the-dreams.de>,
Codrin.Ciubotariu@microchip.com, kamel.bouhara@bootlin.com,
linux-arm-kernel@lists.infradead.org, linux-i2c@vger.kernel.org,
linux-kernel@vger.kernel.org, Nicolas.Ferre@microchip.com,
alexandre.belloni@bootlin.com, Ludovic.Desroches@microchip.com,
devicetree@vger.kernel.org, thomas.petazzoni@bootlin.com
Subject: Re: [PATCH 2/4] i2c: at91: implement i2c bus recovery
Date: Wed, 26 Aug 2020 07:44:02 +0800 [thread overview]
Message-ID: <8deeae50-2d67-d728-7afd-1b8f1b7a927e@electromag.com.au> (raw)
In-Reply-To: <20200825132846.GA1753@kunai>
On 25/08/2020 21:28, Wolfram Sang wrote:
> 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.
>
On my todo list still.
Our system eventually recovers at the moment and the multi-master bus
doesn't contain anything that's time critical to our systems operation.
--
Regards
Phil Reid
ElectroMagnetic Imaging Technology Pty Ltd
Development of Geophysical Instrumentation & Software
www.electromag.com.au
3 The Avenue, Midland WA 6056, AUSTRALIA
Ph: +61 8 9250 8100
Fax: +61 8 9250 7100
Email: preid@electromag.com.au
WARNING: multiple messages have this Message-ID (diff)
From: Phil Reid <preid@electromag.com.au>
To: Wolfram Sang <wsa@the-dreams.de>,
Codrin.Ciubotariu@microchip.com, kamel.bouhara@bootlin.com,
linux-arm-kernel@lists.infradead.org, linux-i2c@vger.kernel.org,
linux-kernel@vger.kernel.org, Nicolas.Ferre@microchip.com,
alexandre.belloni@bootlin.com, Ludovic.Desroches@microchip.com,
devicetree@vger.kernel.org, thomas.petazzoni@bootlin.com
Subject: Re: [PATCH 2/4] i2c: at91: implement i2c bus recovery
Date: Wed, 26 Aug 2020 07:44:02 +0800 [thread overview]
Message-ID: <8deeae50-2d67-d728-7afd-1b8f1b7a927e@electromag.com.au> (raw)
In-Reply-To: <20200825132846.GA1753@kunai>
On 25/08/2020 21:28, Wolfram Sang wrote:
> 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.
>
On my todo list still.
Our system eventually recovers at the moment and the multi-master bus
doesn't contain anything that's time critical to our systems operation.
--
Regards
Phil Reid
ElectroMagnetic Imaging Technology Pty Ltd
Development of Geophysical Instrumentation & Software
www.electromag.com.au
3 The Avenue, Midland WA 6056, AUSTRALIA
Ph: +61 8 9250 8100
Fax: +61 8 9250 7100
Email: preid@electromag.com.au
_______________________________________________
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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-08-25 23:50 UTC|newest]
Thread overview: 45+ 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 ` 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 ` Kamel Bouhara
2019-10-02 14:46 ` [PATCH 2/4] i2c: at91: implement i2c bus recovery Kamel Bouhara
2019-10-02 14:46 ` Kamel Bouhara
2019-10-04 9:35 ` Claudiu.Beznea
2019-10-04 9:35 ` Claudiu.Beznea
2019-10-04 9:35 ` Claudiu.Beznea
2019-10-04 20:39 ` Uwe Kleine-König
2019-10-04 20:39 ` Uwe Kleine-König
2019-10-07 10:17 ` Claudiu.Beznea
2019-10-07 10:17 ` Claudiu.Beznea
2019-10-07 10:17 ` Claudiu.Beznea
2019-10-09 13:55 ` Ludovic Desroches
2019-10-09 13:55 ` Ludovic Desroches
2019-10-09 13:55 ` Ludovic Desroches
2019-10-09 14:01 ` Alexandre Belloni
2019-10-09 14:01 ` Alexandre Belloni
2019-10-10 6:54 ` Ludovic Desroches
2019-10-10 6:54 ` Ludovic Desroches
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
2019-10-21 20:20 ` Wolfram Sang
2019-10-22 7:59 ` Kamel Bouhara
2019-10-24 14:08 ` Codrin.Ciubotariu
2019-10-24 14:08 ` Codrin.Ciubotariu
2019-10-24 14:08 ` Codrin.Ciubotariu
2019-10-24 15:07 ` Wolfram Sang
2019-10-24 15:07 ` Wolfram Sang
2019-10-25 1:14 ` Phil Reid
2019-10-25 1:14 ` Phil Reid
2019-10-25 1:14 ` Phil Reid
2020-08-25 13:28 ` Wolfram Sang
2020-08-25 13:28 ` Wolfram Sang
2020-08-25 23:44 ` Phil Reid [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 ` Kamel Bouhara
2019-10-02 14:46 ` [PATCH 4/4] ARM: at91/dt: sama5d4: " Kamel Bouhara
2019-10-02 14:46 ` Kamel Bouhara
2019-10-15 19:10 ` [PATCH 0/4] i2c bus recovery for Microchip SoCs Rob Herring
2019-10-15 19:10 ` Rob Herring
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