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

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Message-ID: <20140309202841.GB2835@katana>
Date:	Sun, 9 Mar 2014 21:28:41 +0100
From:	Wolfram Sang <wsa@...-dreams.de>
To:	mike.looijmans@...ic.nl
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 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?

Thanks,

   Wolfram


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