From: Mike Looijmans <mike.looijmans@topic.nl>
To: Wolfram Sang <wsa@the-dreams.de>
Cc: <nsekhar@ti.com>, <khilman@deeprootsystems.com>,
<davinci-linux-open-source@linux.davincidsp.com>,
<linux-i2c@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
Mike Looijmans <milo-software@users.sourceforge.net>
Subject: Re: [PATCH] i2c-davinci: Implement a bus recovery that actually works
Date: Mon, 10 Mar 2014 07:54:23 +0100 [thread overview]
Message-ID: <531D619F.5000803@topic.nl> (raw)
In-Reply-To: <20140309202841.GB2835@katana>
On 03/09/2014 09:28 PM, Wolfram Sang wrote:
> On Fri, Feb 28, 2014 at 11:32:05AM +0100, mike.looijmans@topic.nl wrote:
>> From: Mike Looijmans <milo-software@users.sourceforge.net>
>>
>> Having a board where the I2C bus locks up occasionally made it clear
>> that the bus recovery in the i2c-davinci driver will only work on
>> some boards, because on regular boards, this will only toggle GPIO
>> lines that aren't muxed to the actual pins.
>>
>> The I2C controller has the built-in capability to bit-bang its lines.
>> Use this to implement a generic recovery routine that puts the
>> controller in GPIO mode and pulse the clk lines until both SDA and
>> SCL return to a high state.
>>
>> Because the controller must be held in reset while doing so, the
>> recovery routine must re-init the controller. Since this was already
>> being done after each call to i2c_recover_bus, move that call into
>> the recovery routine as well.
>>
>> Tested on a custom board with OMAP-L138, and after this change, the
>> board can recover from chips keeping SDA low.
>>
>> Note: This is an adapted port from 2.6.37 code, and was only tested
>> with that kernel.
>
> What about using struct i2c_bus_recovery_info, so the actual recovery
> logic is taken from the core?
I never knew such a thing existed, but it sounds like a sensible thing to do.
In addition, one could also remove the "sda_pin" and "scl_pin" members from
the platform data struct, as they no longer serve any purpose after this patch.
I won't be doing those changes though. My sponsor's budget is limited, so I'm
just having to do the minimum I can get away with. Maybe someone from TI can
take it further?
Mike.
Met vriendelijke groet / kind regards,
Mike Looijmans
TOPIC Embedded Systems
Eindhovenseweg 32-C, NL-5683 KH Best
Postbus 440, NL-5680 AK Best
Telefoon: (+31) (0) 499 33 69 79
Telefax: (+31) (0) 499 33 69 70
E-mail: mike.looijmans@topic.nl
Website: www.topic.nl
Please consider the environment before printing this e-mail
WARNING: multiple messages have this Message-ID (diff)
From: Mike Looijmans <mike.looijmans@topic.nl>
To: Wolfram Sang <wsa@the-dreams.de>
Cc: nsekhar@ti.com, khilman@deeprootsystems.com,
davinci-linux-open-source@linux.davincidsp.com,
linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
Mike Looijmans <milo-software@users.sourceforge.net>
Subject: Re: [PATCH] i2c-davinci: Implement a bus recovery that actually works
Date: Mon, 10 Mar 2014 07:54:23 +0100 [thread overview]
Message-ID: <531D619F.5000803@topic.nl> (raw)
In-Reply-To: <20140309202841.GB2835@katana>
On 03/09/2014 09:28 PM, Wolfram Sang wrote:
> On Fri, Feb 28, 2014 at 11:32:05AM +0100, mike.looijmans@topic.nl wrote:
>> From: Mike Looijmans <milo-software@users.sourceforge.net>
>>
>> Having a board where the I2C bus locks up occasionally made it clear
>> that the bus recovery in the i2c-davinci driver will only work on
>> some boards, because on regular boards, this will only toggle GPIO
>> lines that aren't muxed to the actual pins.
>>
>> The I2C controller has the built-in capability to bit-bang its lines.
>> Use this to implement a generic recovery routine that puts the
>> controller in GPIO mode and pulse the clk lines until both SDA and
>> SCL return to a high state.
>>
>> Because the controller must be held in reset while doing so, the
>> recovery routine must re-init the controller. Since this was already
>> being done after each call to i2c_recover_bus, move that call into
>> the recovery routine as well.
>>
>> Tested on a custom board with OMAP-L138, and after this change, the
>> board can recover from chips keeping SDA low.
>>
>> Note: This is an adapted port from 2.6.37 code, and was only tested
>> with that kernel.
>
> What about using struct i2c_bus_recovery_info, so the actual recovery
> logic is taken from the core?
I never knew such a thing existed, but it sounds like a sensible thing to do.
In addition, one could also remove the "sda_pin" and "scl_pin" members from
the platform data struct, as they no longer serve any purpose after this patch.
I won't be doing those changes though. My sponsor's budget is limited, so I'm
just having to do the minimum I can get away with. Maybe someone from TI can
take it further?
Mike.
Met vriendelijke groet / kind regards,
Mike Looijmans
TOPIC Embedded Systems
Eindhovenseweg 32-C, NL-5683 KH Best
Postbus 440, NL-5680 AK Best
Telefoon: (+31) (0) 499 33 69 79
Telefax: (+31) (0) 499 33 69 70
E-mail: mike.looijmans@topic.nl
Website: www.topic.nl
Please consider the environment before printing this e-mail
next prev parent reply other threads:[~2014-03-10 6:54 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-28 10:32 [PATCH] i2c-davinci: Implement a bus recovery that actually works mike.looijmans
2014-02-28 10:32 ` mike.looijmans-Oq418RWZeHk
2014-03-09 20:28 ` Wolfram Sang
2014-03-09 20:28 ` Wolfram Sang
2014-03-10 6:54 ` Mike Looijmans [this message]
2014-03-10 6:54 ` Mike Looijmans
2014-03-10 7:26 ` Wolfram Sang
2014-03-10 7:26 ` Wolfram Sang
2014-03-10 10:21 ` Mike Looijmans
2014-03-10 10:21 ` Mike Looijmans
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