linux-kernel - Re: [PATCH] i2c-davinci: Implement a bus recovery that actually works

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Date:	Mon, 10 Mar 2014 07:54:23 +0100
From:	Mike Looijmans <mike.looijmans@...ic.nl>
To:	Wolfram Sang <wsa@...-dreams.de>
CC:	<nsekhar@...com>, <khilman@...prootsystems.com>,
	<davinci-linux-open-source@...ux.davincidsp.com>,
	<linux-i2c@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Mike Looijmans <milo-software@...rs.sourceforge.net>
Subject: Re: [PATCH] i2c-davinci: Implement a bus recovery that actually works

On 03/09/2014 09:28 PM, Wolfram Sang wrote:
> On Fri, Feb 28, 2014 at 11:32:05AM +0100, mike.looijmans@...ic.nl wrote:
>> From: Mike Looijmans <milo-software@...rs.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
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