linux-kernel - Re: i2c-i801 retries on lost arbitration (resent: no gpg)

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Message-ID: <20100430100709.GD3553@swordfish.minsk.epam.com>
Date:	Fri, 30 Apr 2010 13:07:09 +0300
From:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To:	Jean Delvare <khali@...ux-fr.org>
Cc:	"Ben Dooks (embedded platforms)" <ben-linux@...ff.org>,
	Wolfram Sang <w.sang@...gutronix.de>,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: i2c-i801 retries on lost arbitration (resent: no gpg)

On (04/30/10 11:48), Jean Delvare wrote:
> Hi Sergey,
> 
> 
> > Both i2c spec and ICH7 datasheet requires to restart transaction in
> > case of lost arbitration.
> > 
> > "No information is lost during the arbitration process. A master that
> > loses the arbitration can generate clock pulses until the end of the
> > byte in which it loses the arbitration and must restart its transaction
> > when the bus is idle."
> >         
> > Please see the following patch. Is it correct?
> 
> No, it's not. As you wrote above, this is not specific to the Intel ICH
> but a general I2C issue. As such it must be handled in i2c-core and not
> by individual drivers. And as a matter of fact, it is already handled.
> Look at functions i2c_transfer and i2c_smbus_xfer in i2c-core.c, see
> the comments "Retry automatically on arbitration loss", the code is
> already there. It's just a matter of bus drivers properly setting
> adapter->retries (which i2c-i801.c does already.)
> 
Thanks.

> So I don't know which kernel you're using, but with the latest upstream
> kernel, things should work just fine already.
> 

OK. Thanks a lot.


	Sergey

	

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