linux-kernel - Re: [PATCH v3 2/5] i2c: davinci: generate STP always when NACK is received

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Message-ID: <20141204182828.GG7944@katana>
Date:	Thu, 4 Dec 2014 19:28:28 +0100
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Grygorii Strashko <grygorii.strashko@...com>
Cc:	Sekhar Nori <nsekhar@...com>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>, linux-i2c@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Kevin Hilman <khilman@...prootsystems.com>,
	Santosh Shilimkar <ssantosh@...nel.org>,
	Murali Karicheri <m-karicheri2@...com>
Subject: Re: [PATCH v3 2/5] i2c: davinci: generate STP always when NACK is
 received

On Mon, Dec 01, 2014 at 05:34:04PM +0200, Grygorii Strashko wrote:
> According to I2C specification the NACK should be handled as follows:
> "When SDA remains HIGH during this ninth clock pulse, this is defined as the Not
> Acknowledge signal. The master can then generate either a STOP condition to
> abort the transfer, or a repeated START condition to start a new transfer."
> [I2C spec Rev. 6, 3.1.6: http://www.nxp.com/documents/user_manual/UM10204.pdf]
> 
> Currently the Davinci i2c driver interrupts the transfer on receipt of a
> NACK but fails to send a STOP in some situations and so makes the bus
> stuck until next I2C IP reset (idle/enable).
> 
> For example, the issue will happen during SMBus read transfer which
> consists from two i2c messages write command/address and read data:
> 
> S Slave Address Wr A Command Code A Sr Slave Address Rd A D1..Dn A P

Applied to for-current, thanks!


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